2. INTRODUCTION AND EXPLANATORY NOTES, LEG 48, IPOD PHASE OFTHE DEEP SEA DRILLING PROJECT

L. Montadert, Institut Français du Pétrole, 92500 Rueil Malmaison, France,D.G. Roberts, Institute of Oceanographic Sciences, Wormley, Godalming GU8 5UB, Surrey, England

andR.W. Thompson, California State University, Arcata, California

BACKGROUND AND PLANNING OF LEG 48

Unlike many cruises of the Deep Sea Drilling Project,Leg 48 was scientifically planned to drill a number of sitesto systematically address the problems of passive marginevolution. These problems have been discussed in thepreceding chapter. Sites drilled during Leg 48 (Figure 1)were selected on the continental margin of the Bay ofBiscay and on the Rockall Plateau. Both these margins arecharacterized by reduced Tertiary progradation thusenabling safe penetration of the synrift and prerift sedimentsat shallow depths. The two margins also offered a contrastin both age and structure. The margin of the Bay of Biscayapparently formed by rifting at about 130 m.y. and isstructured into a series of rifted blocks and half-grabensoverlain by a thin Cretaceous and Tertiary cover. Thesouthwest Rockall Plateau which was rifted at about 60m.y. B.P. does not show a prominent horst and grabenstructure but, instead, consists of a thick deltaic (?)sequence closely similar to that observed beneath the outerV0ring Plateau off Norway. In order to ensure maximumflexibility in the drilling program, many alternate sites wereproposed and accepted by the Safety Panel. The intentionwas to have the facility to modify the program according tothe first drilling results without reference to DSDP. Thisproved fortunate because the ship's drilling capability wasconsiderably reduced following the loss of the drill string atHole 400A. Although Site 401 was drilled with the readyconcurrence of the Chief Scientist of DSDP, Hole 402A waschosen from the data and site proposals onboard. Thisflexibility again proved useful in drilling Site 404 on theRockall Plateau.

The principal objectives of Leg 48 are given in thepreceding chapter and the individual objectives of each sitein each site chapter.

LEG 48 OPERATIONAL SUMMARY

Leg 48 of the International Phase of Ocean Drilling of theDeep Sea Drilling Project began on 12 May 1976 and ended61.86 days later in Aberdeen, Scotland, on 13 July 1976.During this leg, Glomar Challenger traveled 1935.4nautical miles and drilled 10 holes at eight sites. Waterdepths ranged from 4414 meters to 2317 meters andaveraged 3099 meters. Hole depths ranged from 72.5meters to 831.5 meters and averaged 399.2 meters. A totalof 2995.5 meters was cored and 1230.22 meters of corewere recovered representing some 41.06 per cent (Table 1).

Figure 1. Location of Sites 399 through 406 drilled onDSDP Leg 48.

Time distribution for the leg was 9.65 days in port, 11.41days cruising, and 40.8 days on site. The on-site timeconsisted of 8.6 days tripping, 0.09 days drilling, 20.9 dayscoring, 0.6 days positioning the ship, 0.57 days formechanical downtime, 0.54 days in re-entry operations, 1.8days waiting on weather, and 7.7 days in miscellaneousactivities such as picking up a new drill string and runningdownhole logs.

The most serious problem encountered during the leg wasthe loss of 5056 meters of drill pipe plus the bottom-holeassembly when the pin end of the pup joint attached to theBowen-sub broke shortly after re-entering Hole 400A. Theremaining drill string length onboard effectively restrictedsubsequent drilling operations to depths of less than 3000

L. MONTADERT, D. G. ROBERTS, R. W. THOMPSON

TABLE 1Coring Summary, Leg 48

Hole

399400 l400A-T401

402 l402AJ403

404

405

406

Dates

23 to 24 May24 May to6 June6 June to10 June10 June to16 June20 June to24 June25 June to29 June29 June to4 July4 to 9 July

Latitude

47°23.4'N47°22.90'N47°22.90'N47°25.65'N

47°52.48'N

56°08.31'N

56°03.13'N

55°20.18'N

55°15.50'N

Longitude

09°13.3'W09°11.90'W09°11.90'W08°48.62'W

08°50.44'W

23°17.64'W

23°14.95'W

22°03.49'W

22°05.41'W

WaterDepth (m)

4399439943992495

2339.5

2301

2306

2958

2907

Penetration

72.5_

777.5341.0

137.0469.5489.0

389.0

407.0

8341.0

No. ofCores

21

7428

53552

26

43

53

MetersCored

17.5—

729.5265.0

42.0332.5489.0

243.5

407.0

489.5

MetersRecovered

11.77—

350.86103.22

12.19167.5160.83

74.85

172.05

189.42

Recovery (%)

_-

4838.7

29.050.032.9

30.7

42.7

38.69

meters, requiring a drastic revision of the Bay of Biscaydrilling program.

Logging of single-bit holes was successfully carried outfor the first time during Leg 48. To achieve this, the bit wasattached to a bit disconnect assembly in turn connected tothe standard bottom-hole assembly. During drillingoperations, this bit disconnect assembly was held in placeby removable lugs also held in place by a shifting sleeve. Atthe logging depth, a shifting tool is lowered to move thesleeve from behind the lugs allowing them to fall in, therebyreleasing the bit. This operation was successful on four ofthe five holes that were logged. The exception was Site 406where the bit was released before the shifting tool was used.

Nine beacons were used during the leg and all performedwell with the exception of those used at Site 399. The signalfrom the 16-Hz beacon deployed initially deteriorated somuch that a 13.5-Hz beacon was dropped though this alsogave a weak signal. While attempting to position on thissecond beacon, the signal from the first became stronger.Offsets were dialed in and the first beacon was used again.However, this signal became unusable, and the ship wasmoved to Holes 400/400A where another beacon wasdeployed.

Positioning on this leg was excellent except for theproblems encountered at Site 399. The only other occasionthat the ship moved off position was at Site 404 whenextreme weather conditions made it impossible to holdposition. At Site 401, the ship was held on location inmanual and semi-automatic mode while repairs were madeto the gyro compass. Accurate navigation of the ship duringapproaches to sites was difficult because no speed log wasavailable. This resulted in delays of several hours whileawaiting good satellite fixes.

The heave compensator was not used until Core 74 ofHole 400A had been cut. It was used again at Site 401 andwas taken out for logging. It was put in the string for Site402 and pulled out for logging. At Site 403, it was used andlocked out to assess differences in recovery and penetrationrate. The heave compensator was not used for the balance ofthe leg because of the rapidly changing weather conditionsand the need to be able to clear the mudline quickly.

Re-entry was scheduled only for Hole 400A. Afterdrilling to 5176.5 meters, the drill string was tripped to

examine the bit for the cause of the poor recovery. Afterchanging the bit, the hole was re-entered after positioningfor 1 hour and 23 minutes, although the drill string was lostshortly afterward.

Fourteen heat flow measurements were made of which 10were run while the heave compensator was in the drillstring.

The weather was generally good for much of the leg, butadverse conditions affected operations on two occasionsprematurely terminating logging at Site 403 and drilling atSite 404.

SUMMARY OF SCIENTIFIC RESULTS

Detailed scientific results at each site are reported in theSite Report chapters (Chapters 3 through 7, this volume).Overall synopses have been published previously in bothgeneral and specific form (Montadert, Roberts, et al., 1976;Montadert, Roberts, et al., 1977). At the end of thisvolume, a series of chapters synthesize the results of thecruise in terms of the major problems and processes ofpassive margin evolution.

The following section offers a brief synopsis of the majorscientific results at each site. The general stratigraphy ofeach site is summarized in Figure 2 (in back pocket) whichcan be found in more detail on the superlogs enclosed at theend of the volume.

Principal Results

Site 399Site 399 was drilled as a pilot hole to determine the depth

to which casing could be washed during the intendedsubsequent re-entry hole. Thruster malfunction and beaconsignal deterioration forced a move to Site 400, 0.1 mileeast-southeast before further drilling could begin. Thesection penetrated at Site 399 consisted mainly of olive-graymarly calcareous ooze of Pleistocene age.

Holes 400/400A

Site 400 was drilled at the foot of the MeriadzekEscarpment of North Biscay in 4399 meters depth. The sitewas located in a half-graben forming part of a succession oftilted and rotated fault blocks near the continent/ocean

10

INTRODUCTION AND EXPLANATORY NOTES

boundary. The main objectives were to define the nature ofthe pre-, syn-, and post-rifting environments, the regionalunconformities, the paleoceanography, and the subsidencehistory.

Hiatuses were found between the lowermost Pliocene andthe uppermost Miocene, within the lower Miocene, betweenthe Oligocene and the middle Eocene, between the upperPaleocene and the Upper Cretaceous, and between theCampanian and the Albian. Four lithologic units and eightsub-units were recognized.

Unit 1 (0 to 413 m) comprises nannofossil ooze,nannofossil chalks, and marly ooze and chalk which rangein age from Holocene to early Miocene. Unit 2 (413 to 640m) ranges in age from early Miocene to late Paleocene. As awhole, this unit is less calcareous and contains a muchlarger component of siliceous biogenous remains especiallyin the middle Eocene. Unit 3 (640 to 654 m) comprisescalcareous and marly nannofossil chalks of late Campanianto Maestrichtian age, and is defined at its base by a 30-m.y.hiatus. Unit 4 (654 to 777.5 m), of Albian to late Aptianage, comprises carbonaceous claystones interbedded withcalcareous mudstones. The calcareous mudstones weredeposited by turbidity currents whereas the carbonaceousclaystones correspond to normal pelagic sedimentsdeposited in a deep environment close to the CCD. Theorganic matter is carbonaceous material of terrestrial origin.Because no marine organic matter was found, there is noindication that anoxic conditions existed in the Bay ofBiscay during the Early Cretaceous. The 30-m.y. hiatusseparating the Albian-Aptian "black shales" from theCampanian-Maestrichtian nannofossil chalks is contempo-raneous with the well-known global transgression and sepa-rates formations both of which were deposited in deep wa-ter.

Within the Tertiary, variations in carbonate, biogenicsilica, and clay content along with the observed hiatusesapparently reflect fluctuations in CCD level, bottom currentactivity and surface productivity.

Site 401

Site 401 was situated on the planated edge of a tiltedfault-block underlying the southern edge of the MeriadzekTerrace on the north Biscay margin. The site wascontinuously cored below 84.5 meters and terminated inKimmeridgian-Portlandian shallow water carbonates at341.0 meters.

Four lithologic units were distinguished. Unit 1 (0-20 m)of Quaternary age consists of olive-gray calcareous mud andyellowish brown calcareous ooze. Unit 2 (20 to 171.5 m),of middle Oligocene (or younger) to middle Eocene age,consists of greenish gray nannofossil chalk and marlynannofossil chalk. An 18-m.y. hiatus separates the middleEocene from the uppermost Eocene-lower Oligocene. Unit3 (171.5 to 247.0 m) is of early Eocene to Late Cretaceousage. The Eocene and uppermost Paleocene beds consist ofyellowish brown to orange-brown nannofossil and marlycalcareous chalks. Hiatuses are present between the lowerand upper Paleocene and between the lower Paleocene andthe Maestrichtian. The Maestrichtian to Campanian bedsconsist of laminated nannofossil and foraminiferal calcare-ous chalk. Unit 4 is of late Aptian to Kimmeridgian-Port-

landian age and is separated by a 34-m.y. hiatus from Unit3. Thin upper Aptian oozes comprise the upper part of thesequence and are separated by a large gap from the underly-ing bioclastic limestones which indicate ages from possibleNeocomian at the top to late Tithonian to Berriasian. Thisgap corresponds to erosion during the Early Cretaceous ofthe crest of the tilting block. Intraclast grainstones compris-ing the lowest part of the unit are of Kimmeridgian to Port-landian age.

The presence of shallow water Aptian carbonates incontrast to the carbonaceous claystones and mudstones inHole 400A shows that a substantial submarine relief(—2000 m) existed at the end of the rifting phase. Followingsubaerial erosion during the Early Cretaceous at this site,the deposition of late Aptian chalks in an outer-shelfenvironment indicates that subsidence began in Aptian time.The Campanian-Maestrichtian chalks were deposited in1500 meters depth and the Tertiary beds close to the presentdepth. Discovery of coralline debris in the Kimmeridgian-Portlandian section, in the Tithonian-Berriasian and in theNeocomian, suggests the existence of a large carbonate plat-form dissected by rifting. Less probably the deposition ofthese shallow water carbonates could have been restricted tobathymetric highs forming the top of tilted blocks previous-ly created during the Late Jurassic. Abundant biogenic silicain the middle Eocene section is associated with a decrease insurface and bottom water temperatures and with a promi-nent unconformity marking erosion.

Holes 402/402A

Site 402 was located on the upper slope of the northerncontinental margin of the Bay of Biscay. The mainobjectives were to establish the presence or absence ofshallow water Upper Cretaceous beds, and to penetratepre-Aptian synrift sediments and the upslope equivalent ofthe deep water Albian-Aptian carbonaceous mudstonespenetrated at Hole 400A.

Three lithological units were distinguished: Unit 1 (0 to175.0 m) is composed of Quaternary to middle Miocenenannofossil ooze and siliceous nannofossil chalk of lateEocene age deposited in a bathyal or upper-slopeenvironment. The base of the unit is defined by a hiatus of atleast 55 m.y. between the Albian and middle Eocene. Unit 2(175 to 232 m) is Albian in age and consists of extremelylithified limestones exhibiting sound velocities up to 3 km/s.The main facies include vuggy bioclastic limestones,silicified limestones with large sponge spicules, and afine-grained micritic limestone indicating deposition in ashelf environment. Unit 3 (232.0 to 469.5 m) consists ofcarbonaceous marly limestone, carbonaceous calcareousmuds tone, and carbonaceous marly calcareous chalk ofAlbian and Aptian age. Two major depositional sequencesrecognized in these beds reflect changing environments invery shallow water depths conditioned by the balancebetween a large terrigenous input and subsidence of themargin following rifting.

The Albian-Aptian section may have been deposited aspart of a delta complex built on the subsiding shelf. Theterrigenous "black shale" sediments may have beenderived by reworking of coastal plain sediments colonized

11

L. MONTADERT, D. G. ROBERTS, R. W. THOMPSON

by abundant vegetation. Reduction in the supply ofterrigenous material in late Albian time may indicateinundation of the source by rising sea level. The abnormallithification of the Albian sediments just below the hiatus isascribed to precipitation of silica from silica-enrichedinterstitial water. The middle Eocene sediments arecharacterized by abundant silica and a deep water faunaindicative of deposition in bathyal conditions. The deepwater fauna is contaminated by a displaced shelf fauna andflora containing species indicative of nearshore conditions.This floral evidence of reworking may indicate erosion ofthe shelf, perhaps associated with the global early-middleEocene regression and/or tectonic deformation at that time.

Site 403

Site 403 was drilled on the southwest rifted margin of theRockall Plateau in a sediment-filled basin that strikesparallel to, and lies 30 km east of, the oldest magneticanomaly (24) recorded in the adjacent ocean crust. At thesite, a thick, faulted section of deltaic aspect isunconformably overlain by a thin sequence of sediments,pelagic in their upper part and progradational below. Themain objective of drilling was to determine the nature of theunconformity and the sediments beneath it, and theirrelation to the rifting and spreading history between Rockalland Greenland. The site was abandoned at 489 meterssub-bottom because of torquing in unconsolidated sands.Coring was continuous to total depth.

The section is divisible into three lithologic units andseveral sub-units. Quaternary to upper Miocene nannofossiloozes, foraminifer nannofossil oozes, and chalks occupy theupper 223 meters of section (Unit 1). A 15-m.y. hiatusseparates the upper Miocene and underlying upperOligocene chalks; it may reflect erosion (or non-deposition) by intensive bottom currents followingsubsidence of the Iceland-Faeroe Rise. Deposition rates inthe upper Miocene reached 38-m/m.y. Unit 2 is 47 metersthick and comprises foraminifer nannofossil chalks of lateOligocene and middle Eocene age. The upper Oligocenechalks, a mere 10 meters thick, are grayish green, whereasthe middle Eocene chalks are siliceous and glauconitic. A3-5-m.y. hiatus may separate the middle and lower Eoceneat about 10 meters above the base of the unit. Unit 3,comprising the balance of the recovered section, is a lowerEocene to upper Paleocene series of interbeddedvolcaniclastics and mudstones of shallow marine deltaicaspect. The oldest sediments penetrated are non-fossilif-erous, arkosic sands and sandstones with minor ligniticmudstone and cross-laminated siltstones, of marginal ma-rine or deltaic aspect. Faunal and lithological evidence indi-cates progressive subsidence of the site from a littoral depthin late Paleocene-early Eocene time to outer shelf depths bymiddle Eocene, then to depths in excess of 1000 meters byOligocene time.

Site 404

Site 404 was drilled three miles southeast of the precedingsite, within the same sediment-filled basin on the southwestmargin of the Rockall Plateau, in anticipation that theunconsolidated sands that had prematurely terminateddrilling at Site 403 would not be encountered. A total of 389

meters of section was penetrated, of which the upper 170meters were spot cored.

Three lithologic units were apparent and are consideredequivalent to those at Site 403. The uppermost, Unit 1,ranges in age from Pleistocene to late Miocene, and consistsof a top 28 meters of light brown calcareous mudstone andmarly nannofossil and foraminifer nannofossil oozes, ofPleistocene and late Pliocene age. Pebbles of quartz,feldspar, quartzite, hornfels, and granites within thisinterval suggest ice-rafting. Following an uncored 76meters, the lower part of Unit 1 consists of 95 meters oflower Pliocene to upper Miocene bluish white nannofossiland foraminifer oozes. Unit 2, 28.5 meters thick, is middleEocene olive-yellow to dusky green calcareous porcelanitesand nannofossil porcelanites; siliceous tuffs and glauconiticmudstones are common and contact with underlying Unit 3is transitional. Unlike at Site 403, Oligocene sediments areeither absent or were not recovered at Site 404. Thelowermost lithologic unit, Unit 3, at Site 404 consists of72.5 meters of lower Eocene to probable upper Paleocenesiliceous tuffs, tuffaceous porcelanites, and glauconiticsiliceous limestones, underlain by 99 meters of tuffaceousmudstones. The lowest 30 meters of Unit 3 containsglauconitic sandstones, conglomerates and lignites; the holeended in a tuffaceous conglomerate containing a largeoyster shell fragment. These rocks indicate a near littoralenvironment, probably the top of the deltaic sequence but,by middle Eocene time, the site had subsided rapidly tomiddle bathyal depths. Fresh shards of volcanic glass in themiddle Eocene sediments suggest contemporaneousvolcanism, possibly on the Iceland-Faeroe Rise.

Site 405

Site 405 was drilled at the foot of the east-west-trendingtransform fault which defines part of the southwest marginof the Rockall Plateau. The principal objective of the site(with Site 406) was to examine the structural andstratigraphic evolution of a transform margin also exposedto a subsequent phase of rifting and subsidence as recordedat Sites 403 and 404. The site was cored continuously to atotal sub-bottom depth of 407 meters.

Almost the whole of the Pliocene is unrepresented and ahiatus of about 43 m.y. was present between the upperMiocene and the middle Eocene. Two lithologic units andsix sub-units were recognized. Unit 1 extends from the seafloor to the upper Miocene-middle Eocene hiatus at 65meters. The unit consists of marly foraminiferal nannofossilooze and foraminiferal nannofossil ooze. Unit 2 consists inits upper part of foraminiferal nannofossil ooze, nannofossilooze, and siliceous nannofossil ooze; in its lower part, theprincipal lithologies are well-laminated siliceous mudstoneswith interbedded chert layers. The hole terminated inclaystones of early Eocene age. Dips of up to 30° wererecorded in these lower Eocene sediments. Benthicforaminiferal assemblages of Eocene age are a mixture ofbathyal and upper-slope to shelf species.

Site 406

Site 406 was situated about 5 miles south of 405 and wasdrilled to provide with this site a composite stratigraphicrecord of the history of a transform margin. The hole was

12

INTRODUCTION AND EXPLANATORY NOTES

also designed to penetrate the Pliocene to middle Eocenethat was missing at Site 405. The hole was spot cored to adepth of 413.5 meters and then cored continuously to thefinal sub-bottom depth of 822.0 meters.

Hiatuses were found between the upper and middleMiocene, within the upper Miocene, between the middleOligocene and the upper Eocene, and between the upperEocene and the middle Eocene. Five lithologic units andthree sub-units were recognized. Unit 1 (0 to 71.5 m)comprises rhythmically interbedded calcareous mud, marlyforaminiferal nannofossil ooze and foraminiferalnannofossil ooze. Unit 2 (110 to 557.5 m) consists offoraminiferal nannofossil ooze and chalk of Pliocene tomiddle Miocene age. Unit 3 (557.5 to 617.5 m) of earlyMiocene to late Oligocene age consists principally ofdiatomaceous chalk with interbeds of calcareous diatomite.Unit 4 (617.5 to 765.0 m), of late Eocene age, is calcareouschalks interbedded with diatomites. Slumping is commonwithin the unit. Unit 5 (765.0 to 822.0 m) of middle Eoceneage consists of marly calcareous chalk and limestonesrepresenting the uppermost part of the fan-like bodyobserved on the seismic profiles.

The lower-middle Eocene sediments drilled at Sites 405and 406 are interpreted as a large submarine fan built outfrom the foot of the transform fault in bathyal depths. Thehiatuses are tentatively attributed to periods of intensifiedbottom circulation perhaps associated with wider oceancirculation changes. The alternations of carbonate anddiatomite may indicate local up welling, and the slumpingerosion by bottom currents. The thick section of Miocenecalcareous ooze is probably the product of sedimentdrifting. The seismic and Paleobathymetric data suggest that1.6 km of subaerial relief may have existed along thetransform fault. The total relief of about 5.5 km wasapparently created by Eocene time.

EXPLANATORY NOTES

Responsibility for Authorship

The authorship of Site Report chapters is collectively theshipboard party with ultimate responsibility lying with thetwo chief scientists who rewrote much of these chapters.Chapters 3 through 7 present data and discussions on theholes drilled. However, presentation of the Site Reportsdoes not necessarily follow the format established inprevious DSDP volumes. In Site Report chapters 6 and 7,Holes 403 and 404, and 405 and 406 on the Rockall Plateauare grouped together. The remaining sites are discussed inindividual chapters. All Site Report chapters, however,follow the same general outline (below) with the authorshiplisted in parentheses.

Site Data and Principal ResultsBackground and Objectives (Montadert and Roberts)Operations (Montadert and Roberts)Lithology (Thompson, Auffret, Kagami, Lumsden,

Timofeev, Montadert, Roberts)Biostratigraphy (Bock, Dupeuble, Muller, Schnitker)

Biostratigraphic SummaryForaminifers (Schnitker, Bock, Dupeuble)Calcareous Nannofossils (Muller)Palynology (taken from shore-lab studies)

Physical Properties (Thompson)

Well Logging (Mann, Roberts)Correlation of Seismic Reflectors (Montadert, Roberts)Sedimentation Rates (Muller)Summary and Conclusions (Montadert, Roberts)ReferencesIn preparing the site chapters, exclusive use has been

made of the shore-based studies given in other chapters inthis volume. These are fully acknowledged in the text.Contributions by individual shoreside workers to sections ofthe Site Report also are acknowledged.

Chapters in the volume are grouped under paleontology,sedimentology, organic geochemistry, regional geologicalstudies, and into a series of synthesis chapters designed toprovide an overview of passive margin evolution.Shipboard organic and inorganic geochemical data arediscussed in the chapters by Harrison and Gieskes.

Superlogs

The general practice followed in the Initial Reports of theDeep Sea Drilling Project has been to present the basiclithologic data on core forms appended to each site chapter.Smear-slide and quantitative sedimentologic data haveusually been tabulated separately and dispersed on the coresummary forms. Physical properties data have been treatedseparately.

The shipboard scientific party felt that more use could bemade out of these data and the downhole logs bycollectively presenting them on superlogs which are insertedinside the back cover of this volume. In this way,correlations can be directly observed between, e.g.,carbonate content, sonic velocity, and gamma-ray values.Lithologic units can be readily discerned using thispresentation and subtle changes in lithology presented moreobviously. The superlogs have been drawn at a scale of1/200 to match the optical camera graphic recordings of thedownhole logs.

Data presented on the superlogs are as follows:AgeBiostratigraphic zonation (foraminifers, nannofossils,

and radiolarians)Magnetic susceptibilityNatural remanent magnetizationGrain sizeGamma-ray logCarbonateLithologic units and sub-unitsSub-bottom depthCore recoveryCore numberLithologic logLithologic descriptionDrilling rateSound speed (perpendicular and parallel to bedding)Wet bulk density (a) perpendicular and parallel to the

bedding from GRAPE, (b) determined by chunk andsyringe

Acoustic impedancePorosity and water content

Whenever possible, the electric logs have been tracedonto the superlogs but have been omitted for clarity on thesuperlog for Site 406.

13

L. MONTADERT, D. G. ROBERTS, R. W. THOMPSON

Survey and Drilling Data

The survey data used for specific site selections are givenin each Site Report chapter. On passage between sites,continuous observations were made of depth, magneticfield, and sub-bottom structure. Short surveys were madeon Glomar Challenger before dropping the beacon, using aprecision echo sounder, seismic profiles, and magne-tometer.

Underway depths were continuously recorded on a Gifftprecision graphic recorder (PGR). The depths were read onthe basis of an assumed 800 fathoms/s sounding velocity.The sea depth (in m) at each site was corrected (1)according to the tables of Matthews (1939) and (2) for thedepth of the hull transducer (6 m) below sea level. Inaddition, any depths referred to the drilling platform havebeen calculated under the assumption that this level is 10meters above the water line.

The seismic profiling Teledyne system consisted of twoBolt airguns, a hydrophone array, Bolt amplifiers andfilters, and two EDO recorders which had the same filtersettings.

Drilling Characteristics

Since the water circulation down the hole is an open one,cuttings are lost onto the sea bed and cannot be examined.The only information available about sedimentarystratification between cores, other than from seismic data, isfrom an examination of the behavior of the drill string asobserved on the drill platform. The harder the layer beingdrilled, the slower and more difficult it is to penetrate.However, there are a number of other variable factors whichdetermine the rate of penetration, so it is not possible torelate this directly with the hardness of the layers. Theparameters of bit weight and rp m s a r e recorded on thedrilling recorder and influence the rate of penetration whichis recorded on the superlogs.

Drilling Disturbances

When the cores were split, many showed signs of thesediment having been disturbed since its deposition. Suchsigns were the concave downward appearance of originallyplane bands, the haphazard mixing of lumps of differentlithologies, and the near fluid state of some sedimentsrecovered from tens or hundreds of meters below the seabed. It seems reasonable to suppose that these disturbancescame about during or after the cutting of the core. Threedifferent stages during which the core may suffer stressessufficient to alter its physical characteristics from those ofthe in-situ state are: cutting, retrieval (with accompanyingchanges in pressure and temperature), and core handling.

Shipboard Scientific Procedures

Numbering of Sites, Hole, Cores, Samples

Drill site numbers run consecutively from the first sitedrilled by Glomar Challenger in 1968; the site number isthus unique. A site refers to the hole or holes drilled fromone acoustic positioning beacon. Several holes may bedrilled at a single locality by pulling the drill string abovethe sea floor ("mud line") and offsetting the ship somedistance (usually 100 m or more) from the previous hole.

The first (or only) hole drilled at a site takes the sitenumber. Additional holes at the same site are furtherdistinguished by a letter suffix. The first hole has only thesite number; the second has the site number with suffix A;the third has the site number with suffix B; and so forth. Forexample, if Site 400 had 3 holes drilled they should bereferenced as Site 400 (first hole), Hole 400A (secondhole), and Hole 400B (third hole). It is important, forsampling purposes, to distinguish the holes drilled at a site,since recovered sediments or rocks usually do not comefrom equivalent positions in the stratigraphic column atdifferent holes.

The cored interval is the interval in meters below the seafloor measured from the point at which coring for aparticular core was started to the point at which it wasterminated. This interval is generally 9.5 meters (nominallength of a core barrel) but may be shorter if conditionsdictate. Cores and cored intervals need not be contiguous.In soft sediment, the drill string can be "washed ahead"without recovering core by applying sufficiently high pumppressure to wash sediment out of the way of the bit. In asimilar manner, a center bit, which fills the opening in thebit face, can replace the core barrel if drilling ahead in hardsediments without coring is necessary.

The maximum (full) core recovery in a single coringattempt is 9.5 meters of sediment or rock (Figure 3). Thisconsists of 9.3 meters in a plastic liner that is held within thecore barrel, and 0.2 meter in the core catcher which isscrewed onto the lower end of the barrel. When a core isbrought onboard, the plastic liner and core are cut in1.5-meter sections starting from the top of the recoveredsediment. A full 9.5-meter core thus consists of six full1.5-meter sections numbered 1 to 6 from the top down, ashort (0.3 m) Section 7, and the core catcher at the bottom(see discussion below concerning logging of the corecatcher). In the case of partial recovery (Figure 3), sectionsstill are measured off and numbered from the top of therecovered sediment, however the number of sections willcorrespond to the number of 1.5-meter intervals necessaryto accommodate the length of core recovered. This mayrange anywhere from 1 to 6 with the lowermost sectionusually containing less than 1.5 meters and the core catcher.

On Leg 48, the core-catcher samples were split, thenlogged on the barrel sheets and stored as an additionalincrement (maximum 0.2 m) of sediment at the bottom ofthe lowermost section of each core. Despite some contraryopinions, an attempt also was made to maintainthe non-conventional designation of CC for the catchersamples. The full designation of catcher samples from thisleg thus includes the number of the lowermost section of thecore within which the catcher was logged; for example —400A (site and hole) — 52 (core number) — 5 (sectionnumber) — CC.

The cores taken from a hole are numbered sequentiallyfrom the top down as the coring proceeds. By DS DPconvention, the top of the recovered sediment (top ofSection 1) is assigned the depth of the top of the coredinterval and any unrecovered sediment is represented as avoid at the bottom of the cored interval (Figure 3). The corenumber and its associated cored interval in meters below thesea floor are unique for a hole and are entered into theDSDP computerized data base.

14

FULLRECOVERY

PARTIALRECOVERY

INTRODUCTION AND EXPLANATORY NOTES

PARTIALRECOVERYWITH VOID

1

2

3

4

5

6

7

IK

f.V."

t . *r V ' .

tVv

;:•>.•;

Lv.*

1

111

z

RE

D

OCJ

IΛ

0)

QJ

EI D

σiII

TOP

CORE-CATCHER —*SAMPLE

BOTTOM

CORE-CATCHERSAMPLE

EMPTYLINER

TOP

BOTTOM

EMPTYLINER

CORE-CATCHERSAMPLE

TOP

BOTTOM

Figure 3. Diagram showing procedure in cutting and labeling of core sections.

In the core laboratory on Glomar Challenger, afterroutine processing, the 1.5-meter sections of sediment coreand liner are split in half lengthwise. One half is designatedthe "archive" half, which is described by the shipboardgeologists, and photographed; the other is the "working"half, which is sampled by the shipboard sedimentologistsand paleontologists for further shipboard and shore-basedanalyses.

Samples taken from core sections are designated by theinterval in centimeters from the top of the core section fromwhich the sample was extracted; the sample size, in cm3, isalso given. Thus, a full sample designation would consist ofthe following information:

Leg (Optional)Site (Hole, if other than first hole)Core number

Section numberInterval in centimeters from top of sectionHole 400A-52-3, 122-124 cm (10 cm3) designates a

10-cm3 sample taken from Section 3 of Core 52 from thesecond hole (A) drilled at Site 400. The depth below the seafloor for this sample would be the depth to the top of thecored interval (in this case 559 m) plus 3 meters for Sections1 and 2, plus 122 cm (depth below top of Section 3), or563.22 meters.

Core Handling

The first assessment of the core material was made onsamples from the core catcher.

After a core section had been cut, sealed, and labeled, itwas brought into the core laboratory for processing. Theroutine procedure listed below was usually followed:

15

L. MONTADERT, D. G. ROBERTS, R. W. THOMPSON

1) Weighting of the core section for mean bulk densitymeasurement.

2) GRAPE analysis for bulk density.3) Sonic velocity determinations.4) Thermal conductivity measurements.After the physical measurements were made, the core

liner was cut, and the core split into halves by a wire cutter,if the sediment was a soft ooze. If compacted or partiallylithified sediments were included, the core was split by amachine band saw or diamond wheel.

One of the split halves was designated a working half.Samples, including those for grain-size, X-ray mineralogy,interstitial water chemistry, and total carbon, organiccarbon, and carbonate content were taken, labeled, andsealed. Larger samples were taken from suitable cores fororganic geochemical analysis, usually prior to splitting thecore. The working half was then sampled for shipboard andshore-based studies.

The other half of a split section was designated an archivehalf. The cut surface was smoothed with a spatula toemphasize the sedimentary features. The color, texture,structure, and composition of the various lithologic unitswithin a section were described on standard visual coredescription sheets (one per section), and any unusualfeatures noted. A smear slide was made, usually at 75 cm ifthe core was uniform. However, two or more smear slideswere often made, for each area of distinct lithology in thecore section. The smear slides were examined under apetrographic microscope. The archive half of the coresection was then photographed, both in color and in blackand white. Both halves were sent to cold storage onboardship after they had been processed.

Material obtained from core catchers, and not used up inthe initial examination, was retained for subsequent work,in freezer boxes. Sometimes significant pebbles from thecore were extracted and stored separately in labeledcontainers.

All samples recovered on Leg 48 are now deposited incold storage at the DSDP East Coast Repository atLamont-Doherty Geological Observatory and are availableto investigators.

Procedures Used in the Measurement and Presentationof Physical Property Data

Objectives

Physical properties data derived from cores help theshipboard selection and interpretations of sediment unitsand aid correlation of those units with downhole logs andwith seismic reflectors, thereby providing a means ofextrapolating information beyond the drill sites. With thispurpose in mind the two primary objectives consisted of: (1)relating physical properties of cores to lithology, withemphasis on composition and lithification (includingcompaction and cementation) and (2) correlating lithologyto downhole logs.

Sampling and Measurements

Physical properties determinations on cores (in additionto coring rate) include: temperature, sound speed, wet bulkdensity, sound impedance, porosity, water content, and a

few measurements of shear strength made with the vaneshear equipment on uncompacted sediment within the top160 meters below the ocean bottom. Brief descriptions ofprocedures for sampling and measurement follow. Thereader may consult detailed discussions in the variousshipboard manuals and the publication by Boyce (1976).

Understanding relationships among physical propertiesand lithologies requires close coordination between sampleselection and description of lithology while in progressonboard ship; selection of samples to avoid drillingdisturbance and fractures; careful preparation of samples;and use of the same interval (of 5 to 10 cm), slab, or plug(minicore) for sound speed, bulk density, porosity, andwater content as well as CaCOβ content. Immediatecalculation of sound speed allowed recognition of changesin lithology, more critical examination of the core, andselection of more samples for definition of key beds thatmight help correlation with downhole logs. Measurementsof sound speed (with the Hamilton Frame) and wet bulkdensity (by the 2-minute GRAPE method) on two samplesper section when plotted relative to depth produced logswith striking accord to the lithologic observations and thedownhole logs (see the superlog for Site 406).

Temperature measurements merely involved inserting athermometer into the sediment of the split liner at the timeof sample selection, immediately prior to measurement ofsound speed.

Measurements of compressional sound speed with theHamilton Frame ranged from an average of 2 per core at thebeginning of the cruise (Site 400) up to 10 per core at theend of the cruise (Site 406). The more frequent measure-ments reflected delineation of abrupt velocity changes.Techniques included measurement of uncompacted sedi-ment in the split liners, measurement on slabs of compactsediment removed from the liners and squared with a razoror saw, and measurements on plugs (minicores) cut with thedrill press.

Except in the uncompacted sediment, sound speeds weredetermined both parallel and peΦendicular to the sedimentlayers. Measurements both parallel and peΦendicular to thebeds on 17 samples from the bottom 150 meters of Site 403showed close agreement (within a few per cent and withoutany consistent variation) between sound speeds on slabs andplugs taken from the same slabs.

Measurements of wet bulk density utilized the GammaRay Attenuation Porosity Evaluator (GRAPE) and theweight/volume procedures in the shipboard chemistrylaboratory. Before the cores were split, selected sections,which most nearly filled the plastic liners, were run throughthe continuous GRAPE equipment. In uncompactedsediment the 2-minute GRAPE measurements utilized metalcylinders (Boyce bottles) or the split plastic liner whereasthe weight/volume determinations came from small syringesamples. In compact sediment, 2-minute GRAPE measure-ments and weight/volume determinations both came fromthe same slabs or plugs utilized for the sound speed mea-surements .

The initial procedure was later modified to eliminatemeasurements perpendicular to the beds. Based onexperience from Sites 400, 401, and 402 these extrameasurements wasted time because they showed no

16

INTRODUCTION AND EXPLANATORY NOTES

consistent variations from the measurements parallel to thesediment layers.

Determinations of wet bulk density, porosity, and watercontent in the shipboard chemistry laboratory averaged twoper core. These determinations utilized the same samplesmeasured with the Hamilton Frame and with the GRAPE.

Calculations and Data Tables

Each of the site chapters that follows includes a numericalsummary of physical properties determinations plottedrelative to core interval and sub-bottom depth, includinggeneral lithology and CaCCh. The data tables vary somewhatfrom chapter to chapter, representing the discontinuance ofvane shear measurements after Site 402, measuring the wetbulk density by 2-minute GRAPE only parallel with thebedding after Site 402, and identifying the type of sample (seethe data tables for Sites 405 and 406).

Determinations of sound speed anisotropy and impedanceinvolve simple calculations. The anisotropy appears as anumerical difference between values measured parallel andperpendicular to the sediment layers, and as a percentagedifference between the two. Calculations of sound impedance(sound speed × wet bulk density) include two forms forcomparison: one using an average of densities determined bythe 2-minute GRAPE and the other using the weight/volumedata for density. Both calculations utilize the sound speedsmeasured parallel to the sediment layers on the assumptionthat these would most nearly equal in-situ sound speeds,allowing for expectable decrease in sound velocity due tounloading in bringing the core to the surface. This assumptionapparently was incorrect for some well-cemented rocksbecause the sound speeds measured perpendicular to thesediment layers with the Hamilton Frame agreed with thedownhole sound speeds also measured perpendicular to thebeds (see the superlog for Site 402).

The CaCU3 percentages in the physical propertiessummaries were derived in the shipboard chemistry laboratoryby the carbonate bomb method used on the same samples onwhich physical properties were derived. At Sites 401 and 402the CaCθ3 percentages determined on the physical propertiessamples were consistently lower (ranging from a few per centup to 20 per cent lower) than percentages determined onlithology samples. A variation in drying procedure (a fewhours versus 24 hours for lithology and physical propertysamples, respectively) may have caused this discrepancy.

Downhole Logging

Downhole logging is perhaps best known for its use inpetroleum exploration where it is widely and successfully usedin correlation and stratigraphic studies andin the evaluation offormation fluids and lithology. In deep-sea drilling, theimportance of logging is both great and obvious in determiningin-situ sonic velocities to accurately correlate seismicreflectors with lithology, to compare the shipboarddetermination of physical properties with those measured insitu, and to determine lithologies in areas of poor recovery.However, with the exception of a few holes drilled in theigneous rocks of the Mid-Atlantic Ridge and some earlyattempts during DSDP Legs 7 and 8, there has been no loggingin continental margin areas during the history of the Deep SeaDrilling Project.

For Leg 48, the Institute of Oceanographic Sciences of theNatural Environment Research Council for the Department ofEnergy kindly provided funding for a logging service bySchlumberger Well Services (U.K.) Ltd.

Th e principles of do wnh ole loggi ng and i ts practi ce onboardGlomar Challenger are discussed here to avoid repetition ineach site chapter. Interpretations of the downhole logs aregiven in each site chapter and discussed more fully in aseparate chapter.

Principles of Downhole Logging

The following tools were on board Glomar Challenger forLeg 48:

1) Compensated Neutron Log (CNL) — 3%" O.D.2) Sonic (BHC) — 3%" O.D.3) Compensated Formation Density (FDC) — 33/β" O.D.4) Gamma Ray (GR) — 3%" O.D.5) Variable Density Log (VDL) — 33/s" O.D.6) Induction Resistivity (ISF) — 33/8" O.D.7) Temperature Log — 1*‰" O.D.The brief explanation given below of the principles of

operation of each tool is based on Schlumberger LogInterpretation v. I — Principles (1972).

Compensated Neutron Log (CNL) - Porosity Log

The neutron log is used principally for the delineation ofporous formations and the determination of their porosity.

A radioactive, plutonium-beryllium or americium-beryllium source mounted in the sonde continuously emitsneutrons. These neutrons collide with nuclei in the sedimentand lose energy with each collision. The quantity of energylost per collision is dependent on the relative mass of thenucleus with which the neutron collides. The greatest lossoccurs when the neutron strikes a hydrogen nucleus. Thedeceleration of the neutrons is therefore dependent on theamount of hydrogen in the formation. Successive collisionsdecelerate within microseconds the neutrons to thermal vel-ocities corresponding to energies of around 0.25 electronvolts. The neutrons then diffuse randomly without furtherenergy loss until captured by the nuclei of atoms such ashydrogen, silicon, chlorine, etc. On excitation these nucleiemit high energy gamma rays or neutrons.

The CNL measures these neutron activities at detectors, Niand N2, spaced at 16 and 24 inches from the source (Figure 4).Theratio of the counting rates at these detectors isrelated to thequantity of hydrogen and hence to the liquid-filled pore spaceof the formation. The ratio is processed by a surface computerto yield a linearly scaled recording of neutron porosity indexthat assumes a limestone matrix.

The counting rates at the detectors fluctuate even where theporosity is constant because the collisions are random. Thecount rates are therefore averaged in a time-constant circuit.The appearance and statistical accuracy of the log are thereforefunctions of the setting of the time constant and the loggingspeed. A time constant of 2 seconds and a logging speed of1800 ft/hr yield good quality logs.

It should be noted that the CNL detects all of the water in theformation and not the interstitial water alone. For example, itdetects water chemically bonded to shales. In suchformations, the neutron porosity is greater than the effectiveporosity. Minor corrections to the CNL for borehole size,

17

L. MONTADERT, D. G. ROBERTS, R. W. THOMPSON

Figure 4. Schematic of the compensated neutronlog used principally for delineation of porousformations.

salinity, temperature, and pressure can be derived fromnomograms.

Sonic Log (BHC)

The sonic log is a recording, versus depth, of the time ( t)required for a compressional sound wave to traverse one footof formation. The interval transit time is the reciprocal of thevelocity of the compressional sound wave andis dependent onthe lithology and porosity of the formation.

The Borehole Compensated Log (Figure 5) consists of twopairs of receivers with a transducer above and below. Theelapsed time between transmission of a sound pulse anddetection of the first arrival at the two corresponding receiversare measured continuously. As the speed of sound in the sondeand borehole fluid is less than that of the formation, the firstarrival corresponds to a wavelet that has traveled through theformation.

The transducers are pulsed alternately and the t values readon the pairs of receivers. These values are automaticallyaveraged by computer to cancel errors due to sonde tilt andhole size changes. The transit time is also integrated bycomputer to give the total travel time to aid seismicinterpretation.

Occasionally, a weak first arrival may only trigger the firstreceiver and the second receiver may be triggered by a laterarrival in the same wave train. Spuriously large travel timesthus measured in pulse cycles are shown on the sonic curve asexcursion towards higher t values known as cycle skipping.This phenomenon is likely to occur when the signal is stronglyattenuated by unconsoli dated or heavily fractured formations.

The t data are displayed in units of microseconds per foottogether with the gamma and caliper logs. The integrated

l

UPPER TRANSMITTER

LOWER TRANSMITTER

Figure 5. Schematic of BHC sonde, showing ray paths forthe two transmitter-receiver sets. Averaging the two Atmeasurements cancels errors due to sonde tilt and hole-size changes.

travel time is given by a series of pips recorded at millisecondintervals.

The transit time data can be used to evaluate porosity(Wyllie, 1956, 1958) according to the relation:

t log- tmatf- tma

wheretiog= sonic log value in microseconds per ft,tma= transit time of the matrix material,tf = about 189 s/ft (corresponding to a

"fluid velocity" Vf of about 5300 ft/s).

Compensated Formation Density (FDC)

The Formation Density Log provides direct measurementsof density and is useful as a porosity logging tool.

18

INTRODUCTION AND EXPLANATORY NOTES

The tool consists of a radioactive source which is applied tothe borehole wall in a shielded sidewall skid (Figure 6). Thesource emits medium energy gamma rays which lose energy asthey undergo Compton scattering by the electrons in theformation. The number of Compton scattering collisions isrelated directly to the number of electrons in the formation.Gamma rays reaching the detector at a fixed distance from thesource are counted and give a measure of the electron densityor number of electrons per cubic centimeter of the formation.Electron density is related to the true bulk density, pbgrains/cm3, which is in turn dependent on the density of therock matrix material, the formation porosity and the density ofthe fluid filling the pores.

To minimize the influence of borehole fluids, thesource anddetector mounted on a skid are shielded. The openings of theshields are applied against the borehole wall by means of aneccentering arm. A correction is needed when the contactbetween the skid and the formations is poor. In the chart ofFigure 7, a plot of long-spacing count rate versusshort-spacing count rate is given. Points for a given value of pband various hole conditions fall on or close to an averagecurve. From these average curves, the corrected pb can bederived without any explicit measurement of hole conditions.This correction is made automatically in the FDC and thecorrected pb and the correction, p, are recorded on the log.

Due to the random scattering, the data exhibit statisticalvariations that are smoothed before recording by passing thesignal through a circuit with a time constant adjustable forformation density. The logging speed is chosen so that the toolwill not travel more than one foot during one time constant; themaximum recommended logging speed is 1800 feet per hour.

SCHLUMBERGER LOG INTERPRETATION/PRINCIPLES

Mud UaKes (p ,h ) \X r m c me X

•Formation (p.

'• Long Spacing ;

'. Detector '.

f:'ú•>.v•••>

Short Spacing \Detector '.

Barite

33

39

66

MUD CAKEWITH BARITE

\mcmè\2.0

2.1

2.5

1/4"

π

1/2"

J*

3/4"

*

KX

•^ / ? 3-JL * ^

X / CT MUD CAKE2.6/ M J j WITHOUT BARITE

M T S Smc

Jxr 10

/ 1.75

1/4"

0

D

Δ

112"

a

A

3/4"

•A

2.94

SHORT SPACING DETECTOR COUNTING RATE

Figure 7. "Spine-and-ribs" plot, showing response of FDCcounting rates to mud cake.

The log data are normally presented with the gamma ray andCNL logs. The density log responds to the electron density ofthe formations and the electron density, pe, is proportional tobulk density. For a substance consisting of a single element

(2Z)

Figure 6. Schematic drawing of the dual spacing FormationDensity Logging Device (FDC).

p b

wherepb is the actual bulk density,Z is the atomic number,A is the atomic weight.

For a molecular substance

(2 Z's)p e p b mol. wt.

where Z is the sum of the atomic numbers of the atoms in themolecule.

For a density logging tool, calibrated in a freshwater-filled limestone formation, it can be shown that

p a = l.0704pe- 0.1883where pa = apparent bulk density recorded by the tool.For sandstones, limestones, and dolomites, p a is practicallyidentical to the bulk density.

For a clear formation of known matrix density (pma), ofporosity containing a fluid of average density pi, the formationbulk density, pb is pb = pt + (1 - Φ)Pma

19

L. MONTADERT, D. G. ROBERTS, R. W. THOMPSON

For many pore fluids, the difference between pa and pb issmall and = ^ma~^b , where pa = pb.

ma Pf

Gamma Ray (GR)The gamma-ray log is a measurement of the natural

radioactivity of the formations. In sediments, the gamma-raylog is normally a reflection of shale content becauseradioactive elements are concentrated in clays and shales. Thetool also records the gamma-ray activity of the formationthrough the casing. During Leg 48, the gamma log was used tocorrelate between the various logging runs.

The gamma-ray sonde contains a scintillation counter tomeasure the gamma radiation originating in the volume of theformation near the sonde. The naturally radioactive elementscontained within the sediments emit gamma rays whoseenergies are degraded as they pass through the sediment. Theamount of absorption depends on the density of the sedimentso that less dense sediments will appear to be more radioactive.

The gamma-ray response after correction for holeconditions (diameter, casing, mud weight, etc.) isproportional to the weight concentration of radioactivematerial in the formation.

The number of gamma rays reaching the counter fluctuateseven when the sonde is stationary due to the statisticallyrandom natural emission of gamma rays. To average out thesestatistical variations, various time constants can be selected toaccord with the measured level of radioactivity.

It should be noted that in interpreting the gamma-ray curve,a bed boundary is picked at a point halfway between themaximum and minimum deflection. The recorded depth ofthis point depends on the logging speed and time constant. Forexample, the apparent depth is shifted in the direction the toolis moving with an increase in the logging speed or length oftime constant. The lag is approximately equal to the distancethe counter moves during one time constant.

To avoid excessive distortion of the curve, the recordingspeed is chosen so that the lag is about one foot. The dynamicmeasure point of a gamma-ray logging tool is then taken asbeing located below the counter at a distance equal to the lag.This places the mid-point of a bed-boundary gamma-rayanomaly at the correct depth on the log.

Variable Density Log (VDL)The variable density log provides a qualitative record of

the variable amplitude of sonic wave trains transmitted bysonic sondes.

The wave train is displayed on an oscilloscope, the lightspot of which varies in brightness in proportion to theamplitude of the received acoustic wave. The oscilloscopetraces are photographed onto film moving synchronouslywith the sonde. On the film, amplitude changes are shownby variations in contrast across the film so that dark areascorrespond to positive maxima of the wave form.

The amplitude or variable density log is often used todetect fracture systems in hard formations. In suchformations, the amplitude of the wave is much reduced.However, bedding planes and thin shale interbeds may givethe same response as fractures so that careful comparison ofthe logs with core and drilling data is necessary ininterpretation. Variations in resistivity and porosity can alsodetermine fracturing.

Induction Resistivity (ISF)

The induction log was originally developed to measureformation resistivity in boreholes containing oil-basedmuds. Induction logging devices are focused to reduce theinfluence of the borehole and of the surrounding formations.

The induction sonde consists of several transmitter andreceiver coils, but the principles can be understood byconsidering a sonde comprising single transmitter andreceiver coils (Figure 8).

A high frequency alternating current of constant intensityis sent through the transmitter coil creating an alternatingmagnetic field that induces secondary currents in theformation. These currents flow in circular ground loop pathscoaxial with the transmitter coil. These ground loop currentscreate magnetic fields which induce a current in the receivercoil. The induced current is proportional to the conductivityof the formations. Any signal produced by direct couplingof transmitter and receiver coils is balanced out by themeasuring circuits.

The ISF combination used on Leg 48 included a deepinduction tool focused to measure the resistivity of theuninvaded zone of the formation and a shallow sphericallyfocused array to measure the resistivity of the flushed andtransition zones near the borehole. The spontaneouspotential or difference between the potential of a movableelectrode in the borehole and the fixed potential of a surfaceelectrode was also measured to calculate formation waterresistivity, salinity, and the presence of permeable beds. Agamma-ray log was also run for calibration purposes.

Operational Aspects of Logging on Glomar Challenger

Prior to Leg 48, only logging of re-entry holes had beenfeasible from Glomar Challenger. This was because tools

TRANSMITTEROSCILLATOR

TRANSMITTERCOIL

AMPLIFIERAND

OSCILLATORHOUSING

FORMATION

-BORE HOLE

Figure 8. Basic two-coil induction log system.

20

INTRODUCTION AND EXPLANATORY NOTES

slim enough to pass through the bit were not available, andthere was no method of releasing the bit in hole to allowpassage of the larger diameter conventional logging toolsthrough the drill stem. For Leg 48, Mr. V. Larson, DSDPOperations Manager, developed a special rotary shiftingtool to release the bit at the foot of the completed hole,enabling logging of single bit holes.

All the holes drilled during Leg 48 were single bit holes.After termination of drilling, the holes were prepared forlogging by spotting mud and then pulling the drill stringback to about 100 meters below the sea bed to wipe the holeclean. The drill pipe was then lowered to the terminal depthbefore the shifting tool was run in to release the bit. Afterreleasing the bit, the drill stem was pulled back to about 100meters below the sea bed. It was necessary to suspend thedrill stem at about this depth to support the bottom holeassembly and bumper subs. In consequence, the upper 100to 200 meters of single bit holes cannot be logged using thistechnique.

The logging tools were normally run in the followingcombinations and order: (1) Gamma, Sonic, Caliper; (2)Gamma, Induction SP; (3) Gamma, Neutron, Density.

The logging tools were so contained as to reduce thenumber of runs and to utilize the gamma log as a correlatorbetween the various runs. During logging, the opticalcamera was set to run at speeds of 1/200 and 1/1000. Auseful complement to the logging was the compilation,during drilling, of a summary lithostratigraphic and physicalproperties log at a 1/200 scale.

During logging operations, a number of problems wereencountered that bear relevantly on future logging onGlomar Challenger. The DSDP holes are normally drilledusing sea-water circulation. Although the hole was "wipedclean" and mud was spotted before logging, the toolscommonly failed to reach total depth (TD) indicating thatthe hole was slowly filling. In conventional drilling, usingmud circulation, a mud cake would be expected to form alining to the borehole that would prevent sedimentsloughing downhole. Apart from preventing the logs fromreaching TD, the poor hole conditions frequently caused"bridging" of the hole, requiring spudding by the tool and,on occasions, fresh wiper runs using the drill stem. Aserious effect was to jam the caliper necessitating care ininterpretation. It was found useful to run the caliperdownhole to avoid jamming. In future logging, motorizedfeeler-type calipers may be more useful.

The reliability of several of the logs, notably the densityand neutron logs, is dependent on good borehole conditions.In particular, the hole should be smooth and its diametershould not exceed the 12-inch limit of the eccentralizer usedwith these tools. Due to jamming, the caliper cannot bereliably used as a check on hole diameter to assess thereliability of these data. However, comparison betweenthese logs, the sonic and resistivity curves, and the small pvalues suggests that these logs are reliable. The reliability ofthe variable density log is questionable for the requiredcentralization of ±Vs is unlikely to have been achieved.

Wave motion is shown as "stair stepping" on the logs.The effectiveness of the heave compensator in eliminatingor reducing wave motion is doubtful and complicated by theabsence of a fixed point of reference once the drill pipe is

off the bottom. It should be noted that the 36-inch sheaverequired by the bending diameter of the Schlumberger cableis too large to be used with the heave compensator. Theeffects of the heave compensator on logging speed and thussensor resolution are likely to be variable. A useful additionto the suite of logging tools would be a dipmeter. Taping ofthe logs is considered to be an essential part of any loggingprogram on Glomar Challenger. Data recorded on tape canbe played back in any combination of depth and scale andprocessed using computer and visual display techniques.Depth adjustments and correlations between logs can becarried out more easily. In the poor hole conditions at Site405 for example, the operation of the tools at their limits hasresulted in saturation of the analog curves. However, thereal data are preserved on tape and can be redisplayed byplayback.

It should be noted that depths of the lithostratigraphic logderived from the drillers are usually deeper than thoserecorded on the electric logs. The magnitude of thediscrepancy varies downhole to a maximum of about 9meters. At Site 406, for example, the formation correlationis +9 meters, the drill stem +5.5 meters, and the sea bed+ 3 meters. These discrepancies have several causes. Thedisagreement in the sea bed depth arises from small errors(±1 m) in (reading) the echo sounder and the equivocaldepth of the first core cut at the sea bed; tidal effects maycause a further discrepancy of ±1 meter. There are alsocumulative errors that arise from the measurement of drillpipe lengths and the uncertain position of the core recoveredin each cored interval. Drilled depths determined with thebumper subs closed are also at variance with the drill stemdepth determined with the bumper subs open. The problemof correlation between cores and logs could be considerablyreduced by routine measurement of the natural gamma-rayactivity of the cores using a scanning scintillometer in thelaboratory.

In presenting the logs, no attempt has been made toremove these discrepancies and the lithostratigraphic andelectric logs are displayed relative to a common sea floordatum.

Copies of the logs run on Leg 48 may be obtained bywriting to the Associate Chief Scientist, Science Services,Deep Sea Drilling Project A-031, University of California atSan Diego, La Jolla, California 92093.

Geochemical Measurements

Aboard ship, analyses for pH, alkalinity, and salinity areconducted routinely.

pH is determined by two different methods. One is aflow-through electrode method, the other is a punch-inelectrode method. pH is determined on all samples via theflow-through method, which is a glass capillary electrode inwhich a small portion of unfiltered pore water is passed. Inthe softer sediments a "punch-in" pH is also determined byinserting pH electrodes directly into the sediment at ambienttemperature prior to squeezing. The pH electrodes for bothmethods are plugged into an Orion digital millivolt meter.

Alkalinity is measured by a colorimetric titration of a1-ml aliquot of interstitial water with 0.LV HCl using amethyl red/blue indicator.

Alkalinity (meq/kg) = (ml HCl titrated) (97.752)

21

L. MONTADERT, D. G. ROBERTS, R. W. THOMPSON

Salinity is calculated from the fluid refractive index asmeasured by a Goldberg optical refractometer, using theratio:

Salinity (7oo) = (0.55) AN

where AN = refractive index difference × I04. Localsurface sea water is regularly examined by each of the abovemethods for reference.

Quantitative Sedimentologic Analyses

Smear Slides

The lithologic classification of sediments is based onvisual estimates of texture and composition in smear slidesmade onboard ship. These estimates are of areal abundanceson the slide and may differ somewhat from the moreaccurate laboratory analyses of grain-size, carbonatecontent, and mineralogy. Experience has shown thatdistinctive minor components can be accurately estimated(±1 or 2%), but that an accuracy of ± 10 per cent for majorconstituents is rarely attained. Carbonate content isespecially difficult to estimate in smear slides, as is theamount of clay present. Smear-slide analyses at selectedlevels as well as averaged analyses for intervals of uniformlithology are given on the core description sheets. Forcarbonate content, reference should be made to shipboardcarbonate bomb analyses and shore-based analyses (seebelow).

Carbonate Data

During Leg 48, extensive use was made of the carbonatebomb device as an aid in sediment classification onboardship. This device is basically a cylindrical vessel withpressure gauge in which a sediment sample of knownweight is reacted with acid. The pressure of CO2 generatedis measured and converted to per cent carbonate. Accuracyto within ±5 per cent total carbonate has been quoted for thedevice.

Samples were taken for DSDP shore-basedcarbon-carbonate analysis using the LECO 70-SecondAnalyzer. Results of these analyses are shown on the super-logs.

X-Ray Mineralogical Analyses

X-ray mineralogical analyses of Leg 48 sediments wereprovided by the Société Nationale ELF Aquitaine in Pau,France for the Biscay sites, and by the Centre de Recherchessur l'Environnement (Prof. M. Vigneaux, Directeur) of theUniversité de Bordeaux for the Rockall sites. Analyses bySNPA were made on powdered bulk samples andcomparisons of peak areas yielded percentages of quartz,calcite, dolomite, and anhydrite to an estimated accuracy of±10 per cent. Amounts of feldspar and siderite wereestimated qualitatively. Two types of analyses wereconducted at Bordeaux: (1) bulk samples were pulverizedand analyzed by powder diagrams. Comparison to syntheticreference samples yielded semiquantitative estimates ofquartz, calcite, dolomite, and feldspar (alkali andPlagioclase); and (2) clay fractions (

INTRODUCTION AND EXPLANATORY NOTES

10 20

Percentage of Components

30 40 50 60 70

Nomenclature

80 90 100 Component

Authigenic Components

Siliceous Skeletons

CaCO3 (See text)

Siliceous Skeletons

Silt and Clay

CaCO3

Siliceous Skeletons

Silt and Clay

CaCO3

Siliceous Skeletons

Silt and Clay

CaCO3

Siliceous Skeltons

Silt and Clay

CaCO3

Authigenic Components

Siliceous Skeletons

CaCO3

Terrigenous and Volcanic Detritus

Sediment Type

Pelagic Clay ( a )

Pelagic Biogenic Siliceous

Transitional Biogenic

Siliceous ^ c '

Pelagic Biogenic Calcareous

Transitional Biogenic

(e)Calcareous v

(b)

(d)

Terrigenous Sediments (f)

(a) See descriptive notes in text

(b) Soft - oozes; Hard - radiolarite, diatomite, chert, or Porcellanite

(c) Less than 50% siliceous fossils - diatomaceous (radiolarian) mud or mudstone

Greater than 50% siliceous fossils - muddy diatom (radiolarian) ooze or muddy diatomite (radiolarite)

Greater than 10% CaCO3 - calcareous

(d) Soft - ooze; Firm - chalk; Hard - indurated chalk, limestone

(e) Soft - marly calcareous ooze; Firm - marly chalk; Hard - marly limestone

(f) Soft - clay, mud, silt, sand; Hard - claystone, mudstone, shale (if fissile), siltstone, sandstone

For pyroclastic sediments see text.

Figure 9. Summary chart of lithologic classification for oceanic sediments.

III. Transitional Biogenic Siliceous Sediments10-70% siliceous microfossils30-90% terrigenous components (mud)

mud: muddy diatom ooze (muddydiatomite)If CaCθ3 10 to 30 per cent: appropriate qualifier isused (See III).

IV. Pelagic Biogenic Calcareous Sediments>30% CaCC-330% terrigenous components60 per cent:

soft: calcareous (or nannofossil, etc.) oozefirm: chalk (or nannofossil chalk, etc.)

23

L. MONTADERT, D. G. ROBERTS, R. W. THOMPSON

Pelagic

Non-biogenic

Pelagic Clay

Strip system used in graphic logs to indicate presence

of important minor components (10-50%).

symbol for

main component

symbol for

main component

symbol for minor

component (30-50%)

symbol for minor

component (10-30%)

Siliceous Bioqenic

Pelagic Siliceous Biogenic - Soft

Diatom Ooze

Diatom-Rad or

Radiolarian Ooze Siliceous Ooze

SB1

Pelagic Siliceous Bioqenic - Hard

Diatomite Radiolariate Porcellanite

> *

* 'L v

Δ ΔΔΔΔΔΔΔΔΔΔΔΔ Δ ΔΔΔΔΔΔ

Δ Δ Δ ΔΔ Δ Δ

Δ Δ ΔΔ Δ Δ Δ Δ

Δ Δ Δ ΔΔ Δ Δ

_ A A A, A A A A

A A A A

Transitional Bioqenic Siliceous Sediments

Siliceous Component 50%

tuffaceous

Porcellanite

(10-30% volcanic ash)

diatomaceous

nanno chalk

(30-50% diatoms)

Siliceous Modifier

Symbol and According to

Hard or Soft.

Calcareous Biogenic

Pelagic Biogenic Calcareous - Soft

Nanno-Foram or

Nannofossil Ooze Foraminifer Ooze Foram-Nanno Ooze Calcareous Ooze

Transitional Biogenic Calcareous Sediments

(Examples)

u-~J-—-L-~TJL:

±•£÷±÷±: CBl -mm• ~r T ~r_-r_i_-r_I_-i-_i_-r

DDooDOOOOOO

Pelagic Biogenic Calcareous - FirmNanno-Foram or

Nannofossil Chalk Foraminifer Chalk Foram Nanno Chalk Calcareous Chalk

1 1

1 1

I 11

1 1 1

1 1 I 1

1 1 1 1

I ' I ' II I IIT IT I I II I Iri ii i i I

i ' i ' i ' i

! i ! i ! i ! i :

Marly NannoOoze

Marly NannoChalk

Pelagic Biogenic Calcareous - Hard

Limestone

CB9

Transitional Biogenic Calcareous Sediments

ii

Z i MarlyLimestoneTerrigenous Sediments Qualifiers Letter Overprint (as per examples)^~~- Zeolite Al Glauconite A3 Siderite A4 (other may be designated)

Clay/Claystone Mud/Mudstone Shale (Fissile) Sandy mud/Sandy mud stone Si It/Siltstone Sand/Sandstone

Volcanic BrecciaConcretionsDrawn Circle with Symbol (others may be designated)

MnManganese P = Pyrite Z = Zeolite

Special Rock Types

Gravel Conglomerate Breccia

Carbonaceous or Sapropelic

SRI IIPSR2

BasicIgneous

AcidIgneous

2-10% organic

Figure 10. Key to lithologic and biostratigraphic symbols.

24

hard: limestone (or nannofossil limestone, etc.)NOTE: Sediments containing 10 to 30 per centCaCθ3 fall in other classes where they are denotedwith the adjective "calcareous," "nannofossil," etc.

VI. Terrigenous Sediments>30% terrigenous components

L. MONTADERT, D. G. ROBERTS, R. W. THOMPSON

C. Silicified SedimentsAt Site 405, much of the calcareous mudstoneobtained in Cores 31 to 43 contains in excess of10 per cent opaline silica which is not in the formof recognizable microfossils. Very hard layers inthis section are classified as chert whereas thesomewhat softer portions are termed silicifiedmudstone. The latter are indicated graphically byutilizing the chert symbol in only a fraction of thelithology column. These sediments are thusdistinguished from those indicated as siliceouswherein greater than 10 per cent of recognizablesiliceous microfossils are present, and for whichthe porcelanite symbol was used.

Core Disturbance

Unconsolidated sediments are often quite disturbed by therotary drilling/coring technique, and there is a completegradation of disturbance style with increasing sedimentinduration. An assessment of degree and style of drillingdeformation is made onboard ship for all cored material,and shown graphically in a separate column on the coredescription sheets. The following symbols are used:

Slightly deformed; bedding contacts slightlybent.Moderately deformed; bedding contacts haveundergone extreme bowing.

~^ — " -* ' Highly deformed; bedding completelydisturbed, often showing symmetricaldiapir-like structures.

O O O Soupy, or drilling breccia; water-saturatedintervals that have lost all aspects of originalbedding and sediment cohesiveness.

Consolidated sediments and rocks seldom show muchinternal deformation, but are usually broken by drilling intocylindrical pieces of varying length. There is frequently noindication if adjacent pieces in the core liner are actuallycontiguous or if intervening sediment has been lost duringdrilling. The symbolOOwas used for cylindrical pieces ofcore separated by intervals of drilling breccia or injected(remolded) softer sediment. In some cases (notably Site400) fragments of previously drilled material have sloughedback down the hole and been recored. Such material isindicated by the symbol (OOQ) and labeled as cavings.

Sedimentary Structures

Megascopic sedimentary structures are apparent in manyof the cored sediments. These include primary features suchas lamination, graded bedding, and bioturbation as well assecondary features such as microfaulting. Where it isreasonably certain that these features are not the product ofcoring disturbance, they are logged graphically in a separatecolumn on the core description sheets utilizing the symbolsshown in Figure 12. Caution should be used in drawingconclusions based on the sedimentary structures because itis often extremely difficult to differentiate between naturalstructures and those produced by coring.

Core Description Forms

The basic lithologic and biostratigraphic data aresummarized on core description forms (barrel sheets) which

Parallellaminations

Contorted bedding(not artificial)

Massive or homogeneous(no symbol necessary)

Load casts (HAND DRAWN)

Cross stratification

Gradational contract(HAND DRAWN)

Sharp contact(HAND DRAWN)

Sedimentary clasts OJM JJM>JMJ*

Burrows

Microfaulting ~L

"Gritty" -TT"laminations

Figure 12. Sedimentary structure symbols.

make up the remainder of this volume. Insofar as possiblethe lithologic data for the main lithology are presented in thefollowing order:

Sediment or rock nameColor name and GSA (or Munsell) numberGeneral Description of the core including disturbance,

sedimentary structures and other special featuresComposition from smear slides and/or thin sectionsCarbon-carbonate determinationsGrain-size determinationsX-ray mineralogy

Many cores contain important minor lithologies as well asthe major lithology and descriptive information is includedfor these wherever possible.

An exemplary core description form showing all symbolsand explanatory notes is included herewith (Figure 13) as anaid to understanding and utilizing the core data presented inthe remainder of this volume.

Biostratigraphy

Planktonic foraminiferal zonation presented herein isbased on the number scheme developed by Blow (1969) andBerggren (1972a, b) for the Tertiary and Quaternarysequences. The Mesozoic sequences are zoned according tothe scheme of Sigal (in press) (Figure 14). The calcareousnannofossil zonation follows Martini (1971a, b) for theTertiary and Quaternary. The zonation given by Thierstein(1971, 1973) was used for the Lower Cretaceous. Agedeterminations for the Upper Cretaceous are based on thezonation used by Roth (1973) which combines zonesestablished by Martini (1961), Cepek and Hay (1969),Bukry and Bramlette (1970), and Manivit (1971).

Wherever possible, zone boundaries are based upon thenominate species of the original zone definition. However,in those cases where the nominate species were absent, forwhatever reason, other species have been utilized, ranges ofwhich are reasonably well known from areas where theyoccur together with the nominate species. In severalinstances, in the absence of any diagnostic species, zonalboundaries could not be recognized at all.

Absolute age assignments were made in reference to theNeogene scale of Ryan et al. (1974) and to the Paleogenescale of Hardenbol and Berggren (in preparation). The time

26

INTRODUCTION AND EXPLANATORY NOTES

SITE

ME

-RO

CK

UN

ITlO

ST

RA

TZO

NE

GD

co

IMc

arié

dio

l

cc

cc

c

Ncoc

Man

nopl

i

z

Zo

ne

fera

l

c

εo

LL

LL

H O L E

FOSSILCHARACTER

RA

MS

OLL.

/

SO

NN

<Z

Q<

MDA

RO

FA

CIE

SM

IC

MCEA = AbundantC = CommonF = FewR = RareB = Barren

PRESERVATIONG = GoodM = ModerateP - Pnnr

MICROFACIESSee explantorynotes on b o-strat jraphy

CORE

SE

CT

ION

1

2

3

4

5

6

7

CC

ME

TER

S

-

0.5-—

1.0-—-

-

CORED INTERVAL:

GRAPHICLITHOLOGY

ILL

ING

ST

UR

BA

NC

E

o o

cS

c

o

exp

lan

®öCOCX?OQ

OO

T3

1QJ

T3

if

ra

T3O

11

igh

CO

DIM

EN

TA

R>

RU

CT

UR

ES

.

LU|_

i/>i/>

Sam

ple

|

α>

cöc

nNO

Q.£

CΛ

>

><11

GO

);>

UJ

α>

na

t

s0

c0

.QO||

O(Jm

te

(BO

M

c0

áE

ciu

O1!

CDOücf0

Sed

—II

CO

Slid

e

ra

ECO

II

*

HO

LO

GIC

MP

LE

= -

'o

(Fi

•δ

f>

tru

eke

y to

s

QJ

CΛ

LITHOLOGIC DESCRIPTION

Color code(GSA and Munsell)plus specialremarks

MAJOR LITHOLOGY

Color and general description including

comments on sedimentary structures,

special features of composition, and

interbedded minor lithologies.

Smear Slide (SS) and/or Thin Section (TS)*

Descriptions

Section and depth (2-60)

% components

Carbon-Carbonate Determinations

Bomb: 2-60 % CaCOg

LECO: 2-60 % total carbon, % organic

carbon, % CaCO3

Grain Size (shore based)

2-60 % sand, % silt, % clay

X-ray Analysis (see explanatory notes)

Bulk 2-60 < 2 µ m (partial) 2-60Qtz. Smec.

Cal, III,

Feld. Kaol.

Plag.. Chlor,

Other Zeol.

Silica

*TS = In some cases only the rock name

is given on the barrel sheet, however

detailed thin section descriptions are

listed separately after the barrel sheets

for each site.

Figure 13. Sample core description.

27

L. MONTADERT, D. G. ROBERTS, R. W. THOMPSON

32a[

133aC

MAGNETIC REVERSALS

ABSOLUTE AGES (in connection with column Cl)

10"

70

75-

85-

INTERNATIONAL SCALEand

REGIONAL ZONATIONS

C1C2 D E

^

Bost.polyplacum

Hoplit.vari

Del.delawarensis

Plac.bidorsatum

ZONATION BASED ON FORAMINIFERS

MCs

Git. mavaroensis Bolli

Git. gansseri Bolli

MCs 9

Git. stuarti (J. de Lapparent)/

Git. falsostuarti Sigal

MCs 8Git. calcarata Cushman

\ f ^I I

Git. elevata (Brotzen)/Git. stuartiformis Dalbiez

MCs 7

T UGit. concavata carinata Dalbiez

Gli. concavata (Brotzen)

MCs 5

ADDITIONAL ZONATIONG

Rac.fructicosa(Egger)

Schackoina

Git. convexa Sandidge/Git. manaurensis Gandolfi

11Sig. deflaensis (Sigal)/Sig. carpathica Salaj

ef•| icar.

GENERICMARKERS

H

Globotruncanas. I.

\ Hedbergella

J S 1976

Figure 14. Cretaceous foramini feral zonation of Sigal (19 77).

scale given by van Hinte (1976) was used for theCretaceous.

Some sediments were too hard to wash for microfossils.In these cases, thin sections were made and stratigraphicages were assigned either by: (1) recognition of certainmarker species, or (2) comparison of the entire microfaciesto that in samples from land sections. Ages so determinedare indicated by the symbol M (for microfacies) on thebarrel sheets, and the numbers listed in the microfaciescolumn refer to quantity of thin sections studied.

REFERENCES

Berger, W.H. and Winterer, E.L., 1974. Plate stratigraphy and thefluctuating carbonate line, Spec. Publ. Internat. Assoc.Sediment., no. 1, p. 11-48.

Berggren, W.A., 1972a. A Cenozoic time-scale — someimplications for regional geology and paleobiogeography,Lethaia, v. 5, p. 195-215.

, 1972b. Cenozoic biostratigraphy and paleobiogeog-raphy of the North Atlantic. In Laughlin, A.S., Berggren,W. A., et al., Initial Reports of the Deep Sea Drilling Project,v. 12: Washington (U.S. Government Printing Office),p. 965-1001.

Blow, W.H., 1969. Late middle Eocene to Recent planktonicforaminiferal biostratigraphy. In Brönnimann, P. and Renz,H.H. (Eds.), Internat. Conf. Plankt. Microfossils, 1st, Proc:Leiden (E.J. Brill), p. 199-241.

Boyce, R.E., 1973. Physical properties — methods. In Edgar,N.T., Saunders, J.B., et al., Initial Reports of the Deep SeaDrilling Project, v. 15: Washington (U.S. GovernmentPrinting Office), p. 1115-1127.

, 1976. Definitions and laboratory techniques of com-pressional sound velocity parameters and wet water

28

INTRODUCTION AND EXPLANATORY NOTES

MAGNETIC REVERSALS

ABSOLUTE AGES (in connection with column Cl)

INTERNATIONAL SCALEand

REGIONAL ZONATIONS

CIC2 D E

ZONATION BASED ON FORAMINIFERS

ADDITIONAL ZONATIONG

GENERICMARKERS

H

86

5 ε90

92-

100

105

108•

I

1!

I I

5: •S

-j 3

l i i

^ £

MCs4

Git. sigali Reichel/Git. schneegansi Sigal

Git. helvetica Bolli

Mam.nodosoides

Fog. superstes/Met. gestinianum

Catyc.crassum

I RotaliporaGlobigerinelloidess. str.

Hedb. paradubia Sigal)/Git. praeheh etica (Trujillo)

Calyc.robustwn Rtl. cushmani (Morrow) 0. aumalensis (Sigal)/

Git. algeriana Caron

A cant,rhotomagense

Acant."praecursor'

Mant.mantelli

11Rtl. apenninica (Renz)/Rtl. montsalvensis Mornod

Mant.martimpreyi

Rtl. globotruncanoides Sigal/Rtl. brotzeni (Sigal)

MCs 1

Tun.hugardianus

Mort.perinflatum MCi 27

I IRtl. appenninica (Renz)/Plan, buxtorfi (Gandolfi)

i i

fap | b u

Mort.inflatum

Rtl.ticinensis

(Gandolfi)

Tic. breggiensis (Gandolfi)

Dip.cristatum i 26 I

Hop.nitidus

Hop.dentatus

Hedb. rischi Moullade/Tic. primula Premoli-Silva

Douv.mamillatum

Hedb. planispira (Tappan)

MCi 24

Leym.tardefurcata

Chel. buxtorfi/Diad. nodosocos.tatum

Tic. bejaouaensis Sigal

MCi 23 _L

Tic. praetici-nensis (Sigal)

Chel.subnodosocos tatum

MCi 22 Hedb. trochoidea (Gandolfi)•CId.algerianu~Cushman mdCi21 | AettenDanf

VICi 20 Gld. ferreolensis Moullade

Aco.nisus

MCi 19

Deskdeshayesi

MCi IS

Schk. cabri Sigal

Gld. maridalensis (Bolli)/Gld. blowi (Bolli)

Deskforbesi

Gld.gottisi(Chevalier)lMOV? Gld.duboisi(.Cheva\ier)L

Hedb. similis Longoria fMCi 16(= aff. planispira^in Moullade)

Plan,cheniou-rensisSigal

Gld.barriB. Leit.

^Globotruncanas. str.

~~\ Favusella

f Planomalina

Ticinella

Praeglobotruncana

_^Rotalipora

Favusella

~\Conorotalites

i Ticinellaj Clavihedbergella s.strtPlanomalina

~\Caucasella

_jGlobigerinelloides

J S 1976

29

L. MONTADERT, D. G. ROBERTS, R. W. THOMPSON

A MAGNETIC REVERSALS

M5

Mil

M20

ABSOLUTE AGES (in connection with column CD

10°

120

121

25-

30-

35

INTERNATIONAL SCALEand

REGIONAL ZONATIONS

C1C2 D E

Crio. duvalilPlesiosp. ligatusl

_Bal. balearisCHt. villersianuslSubsay. sayni/Acr. meriani

Heteroceras

Neoc.nodosoplicatuslOlcost.jeannoti

Lytict>ceraswithCrioceratites

LyticoceraswithoutCrioceratitesHimant.trinodosum

Sayn.verrucosum

Kil.campylotoxa

Kil.roubaudi

Thurm.pertransiens

Ber. callisto

Pic. picteti

Her. paramimounum

Dal. dalmasi

Ber. privasensis

Tim. subalpina

ZONATION BASED ON FORAMINIFERS

Ctes. aptiensis

MCi 15

(Bettenstaedl)

"zone innommėe"(? zone a Ctes. intercedens (Bettenstaedt)

MCi 14 I

Oh.

MCi 13

eocretacea (Neagu)= aff. simplex in Moullade

, = 11970 Guill. et Sigal

Cauc. gr. /iαMfemi/cα*Subbotina)• kugleri(Bolli)

MCi 10

Doroth. ouachensis SigalMCi 9 •

Hapl. vocontianus Moullade

MCi 8

Lent, ouachensis Sigal var. bartensteini Moullade/Doroth. hauteriviana Moullade* " ? i l l

Lem.λ gr. eichenbergi Bartenstein et. Brand

VlCi 6 imer‰idiana Bart, Bolli et Kovatcheva

M Ci5.

Lent, busnardoi Moullade

Lent, guttata ten Dam

MCi 4

ADDITIONAL ZONATIONG

GENERICMARKERS

\Sehakoina

_^Clarihedbergella

J

domaine„ ? -, mėditer-

~1 ranėenmeridional

-E-

HedbergellaConorotalites

I Caucasella' Planctoniques

\ Calpionellidae

Tintinnopsella•carpathicadatum

_J Calpionellidae

J S 1976

Note: Explanation of abbreviations is as follows:

Acant.Acanth.Aco.Acr.Arg.Bal.Ban.Ber.Bost.Calve.Chel.Cri.Crit.Dal.Del.Desh.Diad.Dip.Disc.Douv.

AcanthocerasAcanthoscaphitesAconocerasAcriocerasArgonauticerosBalearitesBarroisicerasBerriasellaBostrychocerasCalycocerasChelonicerasCriocerasCrioceratitesDalmasicerasDelawarellaDeshayitesDiadochocera