Browne and Slatt 2002.pdf

AAPG Bulletin, v. 86, no. 5 (May 2002), pp. 841862 841

Outcrop and behind-outcropcharacterization of a lateMiocene slope fan system,Mt. Messenger Formation,New ZealandGreg H. Browne and Roger M. Slatt

ABSTRACT

The late Miocene Mt. Messenger Formation of Taranaki, New Zea-land, consists mainly of well-sorted, very ne to ne-grained thin-bedded sandstone and siltstone deposited in middle- and upper-bathyal water depths. Lithofacies are dominated by turbidite beds,comprising planar-laminated and climbing-ripplelaminated sand-stone and massive siltstone.

These strata were studied in a 200 mthick, 4 kmlong coastaloutcrop section and in two, behind-outcrop boreholes from whichFullbore Formation Micro Imager (FMI) and Platform Express logsand core were obtained. The boreholes were 47 and 105 m deepand were drilled about 100 m behind the cliff outcrop about 150m apart. In addition, a high-resolution seismic reection line wasshot adjacent to the coastal cliff and was tied to the updip outcropexposures.

The outcrop section displays abundant erosional cutout of bedsby scour or channels that considerably limit lateral bed continuity.At a smaller scale, bed continuity is also interrupted by bioturbationstructures.

We interpret the outcrop section as a series of vertically stackedor shingled slope fan or channel-levee/overbank complex deposits,comparable to Mutti type III fans. Comparison of behind-outcropdipmeter, seismic reection proles, and FMI data with outcropdata indicates that three main channel-levee/overbank depositionalunits are present. Siltstone and alternating thin-bedded sandstoneand siltstone that display an upward decrease in dip magnitudeand variable dip orientation on dipmeter logs are interpreted aschannel ll deposits. Vertically stacked, interleaved packages ofthin-bedded, typically planar-laminated sandstone (Bouma Tb di-visions), climbing-ripplelaminated sandstone (Tc), and siltstone(Te) with complex upward-decreasing dipmeter patterns are inter-preted as proximal channel-levee and overbank deposits. Laterally

Copyright 2002. The American Association of Petroleum Geologists. All rights reserved.

Manuscript received May 17, 1999; revised manuscript received July 27, 2001; nal acceptance October30, 2001.

AUTHORS

Greg H. Browne Institute of Geologicaland Nuclear Sciences, 41 Bell Road South,Lower Hutt, New Zealand;[email protected]

Greg Browne is a reservoir sedimentologist atthe Institute of Geological and NuclearSciences (GNS). Until recently, he has beenthe research leader of the petroleum geologyprogram at GNS. His sedimentologicalresearch has specialized in deep-water anduvial successions. Much of that time hasbeen spent working on the Mt. MessengerFormation. Prior to that, he worked for theNew Zealand Geological Survey on variedbasin studies projects. He holds degrees ingeology and geography from the University ofAuckland, New Zealand, and a Ph.D. from theUniversity of Western Ontario, Canada.

Roger M. Slatt School of Geology andGeophysics, University of Oklahoma, Norman,Oklahoma, 73019; [email protected]

Roger M. Slatt is the director of the School ofGeology and Geophysics at the University ofOklahoma (2000 to present). He formerly washead of the Department of Geology andGeological Engineering at the Colorado Schoolof Mines (19922000) and director of theRocky Mountain Region Petroleum TechnologyTransfer Council (19952000). After receivinghis Ph.D. in 1970 from the University ofAlaska, he taught geology for eight years atMemorial University of Newfoundland andArizona State University. He then spent 14years in the petroleum industry with CitiesService Research, ARCO Research, and ARCOInternational Oil and Gas Co. before joiningthe Colorado School of Mines in 1992. He haswritten more than 90 articles and madenumerous presentations on petroleumgeology, reservoir geology, seismic andsequence stratigraphy, shallow marine andturbidite depositional systems, geology ofshale, glacial and PleistoceneQuaternarygeology, and geochemical exploration. He sitson numerous professional society committees,has organized technical conferences for AAPG,and teaches short courses for industry andAAPG on the petroleum geology of turbiditesystems and on applied reservoir

842 Mt. Messenger Formation (New Zealand)

extensive interbedded Tb and Tc sandstone and Te siltstone litho-facies with low-angle dips and little variability on dipmeter logs areinterpreted as distal channel-levee and overbank deposits.

These three depositional settings are important to distinguish,as each exhibits different uid-ow behaviors in an analog reservoir.Comparison of the outcrops with typical subsurface data sets asused by petroleum geologists (logs, core, seismic reection) has pro-vided criteria for distinguishing subtle stratigraphic features that caninuence production from a subsurface reservoir analog.

INTRODUCTION

Since the downturn in the industry in the 1980s, exploration com-panies have realized that a greater degree of quantication is re-quired to determine stratal geometries, petrophysical properties,and testing and renement of depositional models for deep-water,thin-bedded reservoir rocks. In many respects, these parameters arebest determined from well-exposed outcrop equivalents, especiallywhere these are at a scale that is comparable to seismic reectionproles. Recent examples of such studies include Bouma andWick-ens (1994), Chapin et al. (1994), Cook et al. (1994), and DeVriesand Lindholm (1994). The practical difculty in studying moderndeep-water equivalents makes it particularly appealing to study out-crop analogs. In this article we demonstrate the application of com-bined outcrop and behind-outcrop characterization studies as an aidto better understanding thin-bedded, deep-water reservoir lithofa-cies. An added advantage in obtaining behind-outcrop logs, core,and seismic reection data is that the outcrop characteristics can beplaced within the context of typical subsurface data types used rou-tinely by exploration and development personnel.

In the case of the late Miocene Mt. Messenger Formation re-ported here, the lithofacies, stratal geometries, rock petrophysicalproperties, and controls on deposition are similar to those of sub-surface producing reservoirs elsewhere in Taranaki (King et al.,1994; Browne et al., 1996) and in other basins such as the Gulf ofMexico (Browne and Slatt, 1997; Slatt et al., 1998). For these rea-sons, we believe that such a eld study is particularly insightfulwithregard to understanding these types of reservoirs. In addition, out-crop studies such as these may also contribute to our understandingof modern slope fan depositional systems (Hiscott et al., 1997).

PREVIOUS WORK

The study area at Pukearuhe Beach to White Cliffs is locatedapproximately 50 km northeast of New Plymouth on the westcoast of the North Island, New Zealand (Figure 1). Several studieshave documented aspects of the regional stratigraphy of the area(King et al., 1993, 1994; Diridoni, 1996; Hansen, 1996; King andThrasher, 1996; Lindsay, 1996). The coastal Mt. Messenger For-

ACKNOWLEDGEMENTS

The nancial assistance of Amoco, Arco, Con-oco, Exxon, Norsk-Hydro, Petrocorp, Schlum-berger, and Texaco is gratefully appreciated.Funding was also provided (to Browne) by theNew Zealand Foundation for Research Scienceand Technology. Institute of Geological andNuclear Science staff undertook the drilling ofthe two boreholes (we particularly wish tothank D. MacFarlan) and the acquisition andprocessing of the seismic reection prole re-ported here. Bob Davis of Schlumberger Wire-line and Testing is thanked for his interest andassistance in the project. Schlumberger under-took the logging of the two boreholes. Permis-sion to work on the property of R. Bryant isgratefully appreciated. T. Elliston (GNS) as-sisted with contouring data presented in Fig-ure 4. Discussions with colleagues on variousaspects of the study, particularly G. Clemen-ceau, J. Coleman, M. Gardner, N. Hurley, P.King, A. Melhuish, and R. Spang, helped clar-ify several issues related to our study. Figureswere drafted by C. Hume, S. Shaw, and J.Smith (GNS), and by L. Sweezey (ColoradoSchool of Mines). Comments on the manu-script by M. Chapin, P. King, J. Stainforth, andF. Zelt are gratefully appreciated. This article isGNS publication number 2201.

characterization. In 1996 he received theAAPG Distinguished Service Award, in 1999was Esso Australia Distinguished Lecturer, andin 20012002 was AAPG DistinguishedLecturer.

Browne and Slatt 843

Figure 1. Generalized geo-logic map of north Taranakishowing the distribution of theMt. Messenger Formation andthe location of the coastal out-crop section at PukearuheBeach. Inset map AA is a struc-tural cross section from north-east to southwest through thecoastal section showing the on-lap of middle and late Miocenesedimentary rocks onto gray-wacke basement rocks to theeast. The cross section is basedon seismic reection linePR83-14, which is indicated bythe solid line AA on the map.Inset map B shows the locationof the two boreholes (Centraland North) at Pukearuhe Beachused in this article.

mation section comprises two stratigraphic intervals,basin-oor fans and slope fans.

In the north, the stratigraphically lower interval isdominated by thick-bedded, overtly massive sandstoneforming amalgamated units several meters thick (Kinget al., 1993, 1994; Jordan et al., 1994) and thin-bedded(30 cm thick) interbedded sandstone and siltstone(Browne et al., 1996, 2000). The sandstone percentageis high, typically 6095%. Massive siltstone with sub-ordinate sandstone interbeds occur stratigraphicallyabove packages of thick- and thin-bedded units. Col-lectively these units are comparable toMutti type I andII fans (Mutti, 1985).

Together all three lithofacies of the lower strati-graphic interval of theMt.Messenger Formation (thick-and thin-bedded sandstone, together with their over-lying siltstone) form a series of meter to 50 mthicksedimentary cycles (King et al., 1994; Browne et al.,1996). These have been interpreted as fourth-orderlowstand sequences deposited in basin-oor fan set-

tings (King et al., 1994). Foraminiferal evidence sug-gests deposition of these units in lower to middlebathyal water depths (King et al., 1993). Sequenceboundaries in this basin-oor fan association are placedat the base of thick-bedded tabular sandstone units.The tabular sandstones overlie major erosion surfaceswith several meters of erosional relief and occur strat-igraphically above slumped siltstone of the previousfourth-order cycle.

Stratigraphically higher parts of the coastal sectionconsist of well-bedded alternating sandstone and silt-stone, each forming individual beds up to 1.2 m thick.These units are described in greater detail in this articleand are comparable to Mutti type III fans. They havevariable proportions of sand (typically between 20 and85%) and have better developed sedimentary struc-tures within sandstone beds. Previous work by King etal. (1994), Browne and Slatt (1997), Slatt et al. (1998),and Browne et al. (2000) has described the general out-crop characteristics of these units; this article adds a


sizeable amount of subsurface data to these previousinvestigations.

The upper part of the formation (studied in thisarticle) is interpreted as a series of slope fans depositedin middle bathyal (1000600 m) to upper bathyal(600200 m) water depths based on foraminiferal evi-dence presented by G. H. Scott (King et al., 1993).Individual fourth-order sequences are thicker, and se-quence boundaries are less spectacular than in thebasin-oor fan association (see King et al., 1994). Inthe section studied, one sequence boundary is inter-preted at the base of a 2 mthick conglomerate (de-scribed in a following section).

In both basin-oor fan and slope fan parts of thesection, each fourth-order sedimentary cycle is poorlydened in terms of age. On the basis of the regionalbiostratigraphy performed to date, however, it wouldappear that each cycle represents a 100150 k.y. pe-riodicity (King et al., 1993). This led King et al. (1994)and Diridoni (1996) to conclude that the cycles rep-resent fourth-order cyclicity within an overall third-order lowstand fall event.

We prefer to use the term slope fan (after VanWagoner et al., 1988, p. 42) to describe the rocks stud-ied at Pukearuhe Beach, as the commonly used similarterm channel-levee complex implies (at least to us)an individual channel with its genetically associatedlevee beds. We believe that the use of the term slopefan is more appropriate, because in our study area webelieve several stacked channel and levee elements rep-resent several slope fan systems.

The overlying Urenui Formation (not discussedhere) is dominated by thick bioturbated siltstone punc-tuated by clastic lled channels (King et al., 1994).

Sediment supply to the Taranaki Basin was highduring deposition, principally because of rapid rates oftectonic uplift (the Kaikoura orogeny) farther east. Es-timates of sedimentation rates during the late Miocenefor the northern part of the Taranaki Basin are as highas 60 cm/k.y. (King et al., 1993, gure 45). The highsediment supply resulted ultimately in the aggradationand northwestward progradation of the continentalslope across the region from the late Miocene to thepresent day (Browne et al., 2000, gure 2).

STUDY METHOD

This study was initiated in 19941995 through fundingfrom a consortium of companies brought together todescribe superbly exposed coastal cliffs as much as 200

m high along the north Taranaki coast. The exposedrocks are typically well-sorted, very ne to ne-grained, thin-bedded (1.2 m thick and typically0.3m thick) sandstone and siltstone and are considered tobe similar to thin-bedded turbidite reservoir rocks inthe Gulf of Mexico and elsewhere. Several methodol-ogies were used in our analysis.

First, an outcrop-based study was undertaken withthe aim of describing the sedimentology, stratal ge-ometries, and some of the petrophysical aspects of theoutcrop exposures. Stratal geometry work was under-taken with both land-based and helicopter-based colorphotography, assembled into an electronic photo-mosaic database and interpreted on a computer work-station in much the same manner as a workstation in-terpretation of reection seismic records would becarried out. Using both outcrop observations andphotomosaic interpretations, a detailed geometry ofthe section was developed. A complete gamma-ray logwas obtained over the entire approximately 600 mstratigraphic interval by Diridoni (1996) using a hand-held Scintrex GRS-500 scintillometer and was supple-mented by additional handheld scintillometer outcropmeasurements over specic stratigraphic intervals. Inaddition, a smaller study area covering approximatelya 200 m length of beach section was selected for de-tailed sedimentologic description, lateral and verticalbed continuity measurement, and petrophysical prop-erty determinations.

In a second phase of work, behind-outcrop meth-odologies were used. Two stratigraphic boreholes weredrilled through Miocene strata approximately 150 mbehind the coastal cliff exposure, penetrating to adepth of 70 m in the North well and 120 m in theCentral well (inset B in Figure 1). These wells werecontinuously cored at 14 cm diameter, with 47 and105m ofMiocene strata cored in each of the boreholes.The sedimentology of the cores was described, and thecores were logged using Schlumbergers Fullbore For-mation Micro Imager (FMI) and Platform Express logsuites. In addition, a 500 mlong, high-resolution two-dimensional (2-D) seismic reection line was acquiredalong the beach adjacent to the cliff outcrop using a48-channel Sercel 338HR acquisition system.

L ITHOFACIES FROM OUTCROP AND CORE

Conglomerate, sandstone, and siltstone lithologies rec-ognized from the study area are described in the fol-lowing sections and are summarized in Table 1.


Conglomerate Lithofacies

Conglomerate comprises a volumetrically small part ofthe total sediment package. It occurs as a 2 mthickunit along the beach section and as two, centimeter-thick beds in the Central well at 42.93 and 44.0 m. Inboth outcrop and core, clasts up to 50 cm in diametercomprise a range of perigenic and sometimes sideri-tized, rounded to well-rounded sandstone and siltstoneclasts, together with graywacke sandstone and base-ment-derived quartz lithologies. Clasts are supportedby a very ne to coarse-grained sandy, shell-rich ma-trix. The shells include abundant thick-shelled andtypically broken and transport-abraded gastropods andbivalves such as Struthiolaria, Glycymeris, and Crassos-trea. Basal contacts are sharp and erosional into under-lying strata. These conglomeratic strata are interpretedto have been deposited from matrix-supported debrisows.

Sandstone Lithofacies

Sandstone comprises 85% of the total thickness ofstrata examined in outcrop and 26% of the cores. Pet-rographically, the sandstones are litharenites and felds-pathic litharenites with little or no interstitial cement.Rock fragments are dominated by metamorphic grainsand less abundant sedimentary and igneous material(Jordan et al., 1994; King and Thrasher 1996). Severalsandstone lithofacies are recognized.

Massive Sandstone (Ta)In outcrop, beds of massive sandstone occur in associ-ation with conglomerates, occurring either immedi-ately under or a fewmeters stratigraphically above con-

glomerate units. Several beds were encountered in thecore. They comprise a small part (3%) of the totalsediment thickness in both outcrop and core. The mas-sive sandstones consist of beds 2050 cm thick, aremoderately to well sorted, and have grain sizes rangingfrom very ne to medium-grained sand. Bed bases aresharp and typically marked by disseminated shell de-bris and occasional less than 5 cm diameter perigenicclasts. These units are interpreted as high-energy, high-density mass ows, equivalent to the A division of aBouma-type turbidite.

Planar-Laminated Sandstone (Tb)Planar-laminated sandstone comprises 45% of the sed-imentary rocks in the outcrop section and 15% of thecore. The planar-laminated sandstone consists of well-sorted, very ne to ne-grained sandstone and typicallyoccurs in the lower part of individual beds, where itmay constitute more than 50% of the total bed thick-ness. Mean grain size is 0.070.08 mm. Uncommon,primary current parting lineations trend northwest-southeast, consistent with the regional paleoow ori-entation. Borehole image data also show northwest-southeast current orientations (Spang et al., 1997).These beds are interpreted as high-energy, upper owregime plane beds equivalent to the Bouma B divisionof turbidites.

Ripple-Laminated and Climbing-RippleLaminated Sandstone(Tc)Well-sorted, very ne to ne-grained ripple- andclimbing-ripplelaminated sandstones comprise 38%of the lithologies in outcrop and 8% of those in thecores. They typically overlie planar-laminated sand-stone in the same bed and, in most cases, occur as

Table 1. Summary of Sedimentary Facies at Pukearuhe Beach

Sedimentary Facies

MaximumThickness(cm)*

Outcrop(%)

Core(%)

MeanPermeability

(md)*Mean

Grain Size*

Conglomerate 200 Trace Trace Sand to boulderMassive Sandstone (Ta) 50 3 3 459 Medium to very ne sandPlanar-Laminated Sandstone (Tb) 80 45 15 456 Fine to very ne sandRipple- and Climbing-RippleLaminated Sandstone (Tc) 50 38 8 275 Fine to very ne sandLaminated Siltstone (Td) 5 Trace Trace 50 SiltMassive Siltstone (Te) 147 15 74 50 SiltSlumped Beds 50 Trace Trace Sand/silt mix

*Data combined from outcrop and core.


low-angle (bounding set to bed stratication angle typ-ically 515), centimeter-thick, climbing-ripple sets. Insome cases the angle of climb increases as the bed formbecame increasingly aggradational with time. Scoliciaburrows are particularly common in both outcrop andcore and in some cases may extend up to 30 cm down-ward through the bed (Figure 2). Paleocurrents mea-sured in outcrop indicate a paleoow direction towardthe northeast and toward the south, perpendicular to

the regional paleoow direction. The ripple-laminatedand climbing-ripplelaminated sandstones are inter-preted as Bouma C divisions of turbidity currents andrepresent lower ow regime deposition from turbiditycurrents.

Siltstone Lithofacies

The x-ray diffraction analyses indicate that the clay sizefraction of siltstone lithofacies are dominated by illite,with less abundant chlorite and mixed smectite/illiteclays. Two lithofacies are recognized.

Laminated Siltstone (Td)Laminated siltstone was recognized in only one bed(see King et al., 1993, plate 47). The lamination iscaused by millimeter-thick, very ne grained sandpartings.

Massive Siltstone (Te)Massive siltstones comprise 15% of the lithologies inthe coastal section and 75% of the core. They overlieripple and climbing-ripple laminae sets or, less com-monly, planar-laminated sandstone and laminated silt-stones. In addition, many channel bases are linedwith massive siltstone. Centimeter-thick interbeddedrippled or planar-laminated sandstone, isolated centi-meter-size sideritic concretions, and concretionarytuffaceous intervals may occur within the siltstone. Anintense degree of bioturbation is common throughoutthe siltstone, with Anconichnus, Scolicia, Chondrites,Zoophycos, and Rorchacichnus being particularly abun-dant (Manley and Lewis, 1998).

Contorted Beds

Contorted beds are not common through the sectionor core. They are relatively thin (up to 50 cm thick)and include convolute detached sandstone, mudballs,and shelly debris within a muddy matrix. These areinterpreted to be slumped deposits.

STRATAL ARCHITECTURE AND RESERVOIRPARAMETERS

Porosity, Permeability, Grain Size, and SortingRelationships

Considerable data have already been reported on theporosity, permeability, grain size, and sorting of the

Figure 2. A typical Bouma turbidite cycle in the Mt. MessengerFormation at Pukearuhe Beach. The bed in the middle of thephoto displays a basal planar-laminated (Tb) division. It restson a highly bioturbated siltstone (Te division) of the underlyingturbidite bed at the base of the photo. Ripple- to climbing-ripplelaminated sandstone (Tc) in the upper part of the photo,above the hammer, is overlain by bioturbated siltstone withsmall sideritized concretions. Prominent Scolicia burrows occurwithin the Tc sandstone. In one of these burrows, the brokenshell remains of the original progenitor spatangoid echinoid ispreserved at the top of the burrow structure. This indicates veryrapid rates of sedimentation for these climbing-ripplelaminatedbeds. Photo by P. R. King.


Mt. Messenger Formation (King et al., 1994; Jordan etal., 1995; Browne et al., 1996, 2000). Outcrop sand-stone porosity in slope fan facies typically ranges from25 to 35% (Browne et al., 2000). Slatt et al. (1998)found that massive sandstone (Ta) have similar meanpermeability (mean horizontal permeability of 459mdfor 102 measurements) as parallel-laminated (Tb)sandstone (mean 456 md for 141 measurements) frommeasurements of sandstone in core from the twobehind-outcrop boreholes. The Ta and Tb sandstoneshave signicantly higher permeabilities than ripple-laminated and climbing-ripplelaminated sandstone(Tc; mean 275 md for 77 measurements) and siltstone(Td and Te; mean 50 md for 781 measurements). Per-meability therefore tends to be greater in coarsergrained and better sorted sandstone, a relationship thatis described in greater detail in a following section.Similar lithofacies control has been demonstrated forGulf of Mexico turbidites (Slatt et al., 1998).

Permeability and sediment textural relationshipswere examined in the context of a 35 cmthick sand-stone bed (bed S7) between stations 1 and 1 atPukearuhe Beach (for location see Figure 3). The aimwas to determine the variability of permeability withina single bed and the inuences that grain size, sorting,and sedimentary structures might have on the distri-bution of that permeability (Figure 4). The basal 10cm of the bed consists of planar-laminated (Tb) sand-stone, passing upward into a Tc climbing-ripplelaminated sandstone part (Figure 4A). The top of thisbed is cut by a scour surface lined by mud. Horizontalpermeability in bed S7 is higher (between 200 and 750md) in the stratigraphically lower planar-laminatedpart of the bed (Figure 4B), which is also slightlycoarser grained (Figure 4C). Mean grain size deter-mined from outcrop core plugs shows a variable dis-tribution through the bed, with a ning-upward trendtoward the top of the bed (Figure 4C). Sorting is alsobest in the lower part of the bed (Figure 4D). Cross-plots show that permeability is higher in coarsergrained (Figure 5A) and better sorted sandstones (Fig-ure 5B), although the correlation statistically betweenthese parameters is not particularly strong. Low per-meabilities in the lower left part of the bed are relatedto the injection of a small siltstone ame structure intothe sandstone at that location. The northern part of thebed stratigraphically above the ame structure displaysa crescent-shaped permeability distribution, with per-meabilities greater than 400 md (Figure 4B). We in-terpret this area of higher permeability to result fromimproved sorting and slightly coarser grain size of the Fi

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Bedding Cyclicity

A wide range of cyclicity is evident in the section. Cy-clicity ranges from the third- and fourth-order se-quences and sequence tracts described previously tocycles several meters to 1020 m thick (perhaps fth-order scale, and here termed large-scale cyclicity),down to centimeter- to meter-scale individual outcropor bed-scale cycles (termed here outcrop-scalecyclicity).

Large-Scale CyclicityLarge-scale cyclicity occurs at a scale of several tens ofmeters in thickness and is best displayed in the 245 mhigh White Cliffs section (Figure 6). Here, up to sevencycles are evident, each between 15 and 60 m thick.Each cycle is bounded by prominent planar contacts,and each cycle displays an internal, upward thinning ofsandstone beds. The upper part of each large-scale cy-cle consists of siltstone with thin interbedded sand-stone, and one cycle has a prominent, 10 mthick silt-stone cap that can be traced across the outcrop (arrowin Figure 6). Sandstone beds at the base of cycles areconformable with the basal bounding surface of eachcycle, or show onlap onto this surface, or are mounded(Browne and Slatt, 1997, gure 8). Commonly, theindividual cycles display opposing dip angles and ori-entations. These stacked units are represented in bothoutcrop and high-resolution seismic reection prolesas a series of thin, well-stratied sedimentary packagesthat have mutually opposing orientations (Figures 7,8). We interpret these large-scale cycles as episodicpulses of sediment in which the supply of sedimentwaned through time. The mounded morphology withdownlap on either margin is interpreted to represent across section of individual slope fan lobes. The angulardiscordance between the packages suggests they rep-resent discrete slope fan lobes that coalesce with pre-ceding lobes.

Figure 4. Plots of bed S7 at Pukearuhe Beach between stations 1 and 1 (location shown in Figure 3). The bed is 35 cm thick,and the upper surface is marked by a major erosional surface. At the eastern margin of the outcrop, the erosion surface erodes intobed S7 and ultimately removes the sandstone bed. (A) Sedimentologic features and locations of horizontal core plugs (solid dots)used in the study. (B) Contoured permeability (in md) based on horizontal core plug measurements. (C) Contoured mean grain size(in lm) based on horizontal core plug measurements. (D) Contoured sorting (plotted as a coefcient of sorting) based on horizontalcore plug measurements. Permeability measurements were made with a Temco minipermeameter; grain size data were determinedusing a laser counter.

Figure 5. Permeability (in md) plotted against (A) mean grainsize (in lm) and (B) sorting (expressed as a coefcient of sort-ing) relationships for sandstone bed S7 at Pukearuhe Beach.Measurements were made on horizontal core plugs: perme-ability measurements were made with a Temco minipermea-meter; grain size data were determined using a laser counter.

Outcrop-Scale CyclicityAt an outcrop scale, cyclicity includes thinning-upwardand thickening-upward cycles comparable to thosedescribed previously, down to individual bed-scale cy-clicity at a Bouma turbidite bed scale (described pre-viously). In the detailed study area (Figure 3), thinning-upward and thickening-upward cycles up to 10m thickoccur, with bases that are either planar and conform-able or highly erosive into underlying strata. Thethicker beds at either the basal or upper parts ofthe respective cycles are typically Tb and Tc sand-stones. Even the conformable bases of these cycles can


generally be traced to sharp, erosional surfaces. We in-terpret these surfaces to represent either changes insediment supply or shifting of channel and adjacentlevee positions, with the ning-upward cycles repre-senting waning channel ll, perhaps as a channel sys-tem migrated away; coarsening-upward cycles are in-terpreted to represent increased sedimentation as thechannel migrated toward the site.

Bed Continuity

Depositional Bed ContinuityIn outcrop, beds are laterally continuous for tens ofmeters and show only slight changes of thickness overthe extent of outcrops. Many beds probably extendmuch farther than the outcrop limits. Lateral bed con-tinuity within outcrops is controlled by erosional trun-cation by channels, rather than by depositional thin-ning or pinch-out of beds. For example, in the detailedsection (Figure 3), only 4 of the total 82 sandstone bedsmeasured display depositional terminations. In con-trast, 21 of the sandstone beds are cut out at scoursurfaces.

Scour surfaces are commonly mud lined (typicallyby 50 cmthick bioturbated siltstone) and range

from low-angle surfaces that cut out a few beds tochannels that are at least 20 m deep. The larger scours(see Browne and Slatt, 1997, gure 12) may be linedwith intraformational clast conglomerate and are lledin their basal parts with thicker (up to 10 m thick)bioturbated siltstone. Sandstones occur in the basalparts of channel lls as thin, rippled beds, increase up-ward in abundance and thickness, and ultimately be-come the dominant lithofacies. Abundant scour and llis evident throughout the channel ll succession.

Other than the 20 mdeep channel described pre-viously, the remainder of the channels present in theMt. Messenger Formation are up to 135 m wide and 5m deep (Table 2). These dimensions are considerablysmaller than channels described from other channel-levee settings (Walker, 1985). Mt. Messenger chan-nels, however, have aspect ratios (width:depth or x:zcoordinates after Cossey [1994]) that average 23:1,similar to aspect ratios reported from elsewhere, suchas the Karoo Basin, South Africa (Bouma andWickens,1991), the Zerrissene system, Namibia (Swart, 1992),the Marnoso-Arenacea Formation, Italy (Ricci Lucchi,1984), and the Tabernas Basin, Spain (Cossey, 1994).

An example of the complex multiple scour and llnature of these erosional cuts is indicated in Figure 9

Figure 6. Oblique aerial view of the northern part of the White Cliffs section (for location see Figure 1). The cliff is up to 245 mhigh in the center of the image. Several depositional cycles (large-scale cycles as described in the text) can be seen in the section. Aprominent horizontal surface is evident in the upper part of the outcrop (arrowed), reaches beach level at the far end of the right-hand end of the photo, and is interpreted as a sequence boundary. For detail see Browne and Slatt (1997, gure 8). Material shownin Figures 714 are from the right (southern) margin of the White Cliffs section. Photo by L. Homer.


and in Browne and Slatt (1997, gure 10). In Figure9B, four major sedimentary packages (labeled IIV) areevident, separated by a series of simple or compounderosional surfaces (labeled from the oldest [1] toyoungest [5]). The stratigraphically lowest interval(package I in Figure 9B) consists of thin sand bedsinterbedded with thicker muds that are truncated bytwo erosional surfaces (labeled 1 and 2) that either aredistinct or are amalgamated into a compound surface.Within package II, thin-bedded sands in siltstone onlaperosion surfaces 1 and 2 and, in turn, are truncated byerosion surface 3. Erosion surface 3 to the southwest

blends with erosion surfaces 1 and 2. A younger sedi-mentary package (labeled III in Figure 9B) overlies ero-sion surface 3 and has an erosion surface (labeled 4 inFigure 9B) that postdates surface 3 to the northeast butis a surface that combines with the other erosion sur-faces (13) to the southwest.

Biogenic ContinuityBioturbation is so intense, particularly within siltstonelithologies, that in places it has caused considerable beddisruption and homogenization. Some burrows, par-ticularly Scolicia, completely pass through sand beds

100 120 140 160 180 200 220 240 260 280 SP0.0

100 msec

200 msec

300 msec

A

B

B

C

D

D

E

PukearuheConglomerate

NW SE Figure 7. Approximately500 mlong, 2-D seismicreection line acquired alongPukearuhe Beach. It shows aseries of slightly angular discor-dant sedimentary packages,each marked by bounding sur-faces (labeled AE). These areinterpreted as a series of inter-leaved levee elements of theslope fan. Interval imaged is ap-proximately 300 m thick.


that are as much as 30 cm thick. Lateral spacing be-tween burrows is as little as 1020 cm. If they weremore abundant, such burrows could greatly reduce lat-eral bed continuity.

DISCUSSION

Lithofacies Associations

In this article, we recognize three main channel-leveeand overbank lithofacies associations from outcrop andsubsurface data: channel, proximal channel-levee andoverbank, and distal channel-levee and overbank (sum-marized in Table 3). These three associations are re-garded as channel axis and channel margin, levee crest,and levee to levee toe, respectively. Although theterms proximal and distal have been used in thepast (Walker, 1985; King et al., 1994; Roberts andCompani, 1996; Manley and Lewis, 1998; Slatt et al.,1998), they have not been widely recognized in sub-

Figure 8. Photo of distal channel-levee and overbank deposits at Pukearuhe Beach showing, in cross section orientation, severalinterleaved packages of thin-bedded sandstone and siltstone. The photo was taken approximately 800 m north of the detailedmeasuredsection locality shown in Figure 3. Cliff is approximately 50 m high. Photo by P. R. King.

surface studies. We present here criteria for recogniz-ing such units using both outcrop and subsurfacemethods.

Channel AssociationChannel morphologies range from single scour and llentities to multiple scour and ll bodies. The associa-tion represents channel axes and channel margin faciesand is spatially restricted in the overall sedimentarypackage of slope fan deposits at Pukearuhe Beach.

Sedimentary rocks lling these channels bothdrape and onlap onto the channel bases. Channels arelled by a variety of lithologies, including conglomer-ate, planar-laminated sandstone (Tb), climbing-ripplelaminated sandstone (Tc), and massive siltstone (Te)(Figure 10). In outcrop, the basal parts of channel llsare dominated by siltstone (unit 5B; terminology de-ned in Table 2), with sparse thin-bedded sandstoneand tuff beds. Interbedded sandstones and siltstoneswith well-developed Bouma divisions (units 3A2, 3B1,3B2, and 3D; nomenclature after Table 2) overlie basal

Table 2. Summary of Outcrop Channel Features, Pukearuhe Beach

Depth (m) Width (m) Width:Depth Ratio Type of Channel Fill* Fill Relationships

5.0 100 20:1 3A overlain by 3B1 and 3B2 onlap2.4 30 13:1 3B1 overlain by 3D onlap1.9 45 24:1 5B overlain by 3D and 3B onlap1.9 34 18:1 3D drape2.4 40 17:1 3D onlap and drape1.0 40 40:1 5B with conglomerate lag onlap1.6 30 19:1 3B1 and 3D onlap1.4 20 14:1 3D onlap2.9 135 47:1 3B1 and 3D onlap and drape

Mean 2.3 53 23:1

*Key to lithofacies scheme (modied from Zelt and Rossen, 1995): 3A thick-bedded amalgamated sandstone (30 cm thick); 3B thick-bedded nonamalgamatedsandstone (30 cm thick); 3B1 thick-bedded nonamalgamated sandstone (0.31.0 m thick); 3B2 thick-bedded nonamalgamated sandstone (1.0 m thick);3D thin-bedded nonamalgamated sandstone (30 cm thick); 5B siltstone with thin (15 cm thick) sandstone/tuff beds.

(A)

(B)

Figure 9. (A) Photo and (B) interpretive sketch of complex cut and ll structures at Pukearuhe Beach (between stations 11 and 15)within distal channel-levee and overbank strata (for location see inset map in Figure 3). Several sedimentary packages (labeled IIV)are separated by multiple phases of cut and ll; each of these erosional surfaces is numbered in chronological order from oldest (1)to youngest (5). Thin sandstone beds interbedded within the siltstone-dominated lithofacies are labeled from the top (S47) to base(S57).


Table 3. Summary of Lithofacies Associations, Pukearuhe Beach

Association Sand (%)Dominant

Sandstone Type Bedding Geometry Log Facies Comments

Channel 2580% Tb or Tc (canincludeconglomerate)

Large-scale scourwith multiplescour and ll

Upward-decreasing dipmagnitude and variableorientation

Fill drapes and onlapsbase; basal portionoften dominated bysiltstone

Proximal 2080% Tc dominant; Taand Tb sandstoneless common

Medium-scaleerosionalsurfaces common

Meter-scale upwarddecreasing dip withconsistent azimuths

Scour surfaces oftenlined with siltstone

Distal 1550% Thin Tb and Tcsandstones; Tasandstones rare

Small-scaleerosionalsurfaces common

Low-angle dips with litlevariation in dipmagnitude ororientation; littlevariation in gamma

Siltstone-dominated;relatively thin sandstonebeds

Figure 10. Photo of channel association at Pukearuhe Beach road end. Channel contact extends from upper left to lower right.Flat-lying alternating sandstone and siltstone turbidites beneath the channel appear adjacent to the stream. Channel-lling sedimentaryrocks to the right (at beach level), begin with siltstone with minor interbedded sandstone, overlain by alternating sandstone andsiltstone turbidites. Upper part of 30 mhigh cliff consists of Quaternary deposits (marked by vegetation). Photo by L. Homer.


predominantly of siltstone with less abundant inter-bedded sandstone, which are relatively continuousacross the outcrop for at least several hundred meters,but display broad-scale stacked or shingled beddingpackages (Figure 8). The lower part of the dipmeterlogs in both the Central and North boreholes consistsof low-angle dips with little variation in either dipmag-nitude or orientation and in gamma-ray values; this isconsidered to be representative of the ne-grained dis-tal association. Thin breaks in dipmeter patterns arethought to represent boundaries of interleaving distallevee packages (Figure 11).

In outcrop, the distal association is dominated byintensely bioturbated Te siltstone up to 147 cm thick,with thinner Tb and Tc and sparse Ta sandstone (Fig-ure 9). The proportions of Tb to Tc sandstone vary inboth outcrop and core, but typically Tb sandstones areslightly more common (Figure 12). Sandstone bedscomprise between 25 and 50% of the distal associationin outcrop.

The distal channel-levee and overbank rocks areequivalent to Mutti facies C, D, and E turbidites de-scribed by Mutti and Ricci Lucchi (1978) and to lith-ofacies interpreted as levee and overbank sedimentaryrocks in theWheeler Gorge, California (Walker, 1985)and the Ram/Powell eld described by Clemenceau(1995).

Depositional Model

The outcrop and subsurface data sets obtained in thisstudy indicate that the Pukearuhe Beach section com-prises a series of vertically stacked depositional ele-ments that range from within channel to proximal anddistal channel and levee lithofacies associations. Lith-ologic elements in this study area are complex and in-terngering, and we believe that we are dealing withseveral slope fan systems rather than one through-going channel with associated levee-anking bedswithin one slope fan. We envisage a depositional set-ting toward the base of the slope, in which several rela-tively small slope fan systems coalesce (Figure 15). Theinterngering of these fan cones produced a series ofshingled slope fan depositional elements that includedproximal and distal channel and levee elements of suc-cessive fan systems (Figure 15).

Modern Geologic Analogs

The interpretation given in the previous section is simi-lar to that modeled for the modern Amazon Fan

siltstones and can be seen to onlap the channelmargins.Sandstone beds comprise a variable proportion of thechannel association between 25 and 80%.

In core, channel bases may be marked by a promi-nent erosive surface and/or by a conglomeratic lag. Ondipmeter logs, an upward-decreasing dip magnitudeand variable dip orientation (upper 12 m in Centralwell in Figure 11A) characterize the channel-ll asso-ciation. In core, planar-laminated sandstone (Tb) is themost commonly occurring lithofacies in channel lls,with less abundant ripple- and climbing-ripplelaminated sandstone (Tc), and massive sandstone (Ta)(Figure 12). In outcrop, Tb and Tc are the more abun-dant lithofacies (Figure 12). Similar channel-ll facieswere described from the L sand channels of the Ram/Powell eld by Clemenceau (1995).

Proximal Channel-Levee and Overbank AssociationProximal channel-levee and overbank deposits are rep-resented by a series of vertically stacked and shingledbedding packages with discordant bedding orientationsthat display evidence for multiple scour and ll events(Figure 13). We predict that the intensity of scouringis greatest at the levee crest near to the channel axes(within tens to hundreds of meters), so we refer to thisas a proximal channel-levee and overbank association.In outcrop, the association consists of a series of meter-deep to several metersdeep scours, which are lled bysedimentary rocks that thin and grade upward intomuddier and lower angle depositional ll (Figure 14).Dipmeter log characteristics (upper 17 m of Northwell in Figure 11B) consist of a series of relatively thin(meter scale), upward-decreasing dip patterns withrather consistent dip azimuths, representing successivestacked and discordant units.

In outcrop, lithofacies are dominated by ripple- andclimbing-ripplelaminated Tc sandstone and less abun-dant massive Ta sandstone and planar-laminated Tbsandstone (Figure 12). Sandstones comprise between60 and 80% of the proximal association in outcrop sec-tions. In core, proximal channel-levee and overbankde-posits in the upper interval of the North borehole havemore planar-laminated sandstones (Tb) than ripple-laminated and climbing-ripplelaminated (Tc) sand-stones or massive sandstone (Ta) beds (Figure 12).

Distal Channel-Levee and Overbank AssociationDistal is a relative term, taken here to mean beds thatare deposited on the levee to levee toe, some distance(greater than a few tens to hundreds of meters) fromthe channel system. Distal channel-levee strata consist


Figure 11. Lithologic log, permeability plot, gamma-ray prole, and dipmeter logs for (A) Central and (B) North boreholes atPukearuhe Beach. An interpretation of lithofacies association is indicated on the right. The boreholes are located at the top of thecoastal terrace and are 150 m apart (see inset B in Figure 1). The Central well is 125 m from the coastal cliff (New Zealand geodeticdatum coordinates 2641971.179 6255898.998); the North well is 150 m from the coastal cliff (2642097.343 6255976.115).

system (Damuth et al., 1983, gure 3). Damuth et al.(1983) recognized several shingled channel-levee com-plexes that were up to 75 kmwide and several hundredmeters thick that rest above medium- and coarse-grained sheetlike sand units or high amplitude reec-tion packets (HARP) (Flood et al., 1995; Hiscott et al.,1997). In the Mt. Messenger outcrop, the HARP faciesrelate to thick basin-oor fan sandstones developedstratigraphically below the slope fan interval describedhere. Although the Amazon lateral scale is much big-ger than the Miocene examples described in this arti-cle, the morphologic relationships appear to be analo-gous (Hiscott et al., 1997).

Carter et al. (1994) described a series of seismicreection proles through the deep-water Bounty Fan.Although the Bounty Fan depositional setting is con-siderably deeper than is inferred for the Mt. Messenger

Formation and is different in scale, many similar mor-phologies are apparent. The Bounty Channel has ank-ing levee lithofacies that in proximal regions displayscour and ll morphologies and sediment migrationpackages. The former, strongly channelized morphol-ogy equates to our proximal channel-levee lithofaciesassociation and is well represented on the left levee(looking down-channel) of the Bounty system. Thisbedding package changes laterally and more distallyinto parallel reectors that lack major scour features,and it appears to be analogous to our distal channel-levee lithofacies association.

Producing Reservoir Analogs

Several features from the Mt. Messenger Formationare similar to ne-grained, mud-rich, thin-bedded

Bouma TaBouma TbBouma TcBouma TdBouma Te% sand

Puke

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90 90 90

80 80 80

70 70 70

60 60 60

50 50 50

40 40 40

30 30 30

20 20 20

10 10 10

0 0 0

Channel Association Proximal Association Distal Association(A) (B) (C)

Figure 12. Abundance of Bouma divisions (Ta, Tb, Tc, Td, and Te) from outcrop and drillhole data for each lithofacies association:(A) channel, (B) proximal channel-levee and overbank, and (C) distal channel-levee and overbank. The plots show the percentage ofBouma divisions occurring at each outcrop or borehole locality and the total percentage of sand present. The value T (in parentheses)represents the total thickness (in centimeters) of beds at each outcrop or borehole site.


Figure 13. Photograph ofproximal channel-levee andoverbank association,Pukearuhe Beach. Severalstacked channel-ll elementscan be recognized, comprisingalternating sandstone and silt-stone or dominantly siltstone lltypes. One channel, exposed atbeach level, is lled with bothperigenic sandstone and silt-stone and basement graywackeand quartz clast types (thePukearuhe conglomerate). Thephoto was taken approximately250 m south of the detailedmeasured section localityshown in Figure 3.

turbidite reservoirs of the Ngatoro and Kaimiro elds,New Zealand (for details see King et al. [1994]), andthe Gulf of Mexico (see Browne and Slatt, 1997).Based on published literature, there are signicant sim-ilarities between the Mt. Messenger Formation and, inparticular, the Ram/Powell and Mahogany elds of theGulf of Mexico.

Ram/Powell Field, Gulf of MexicoThe Ram/Powell eld is a large, stratigraphicallytrapped oil and gas discovery of middle Miocene age.The L sand reservoir is a large, channel and levee com-plex, in which the hydrocarbons are trapped in theeastern levee (Rossen and Sickafoose, 1994; Clemen-ceau, 1995; Clemenceau et al., 2000). That work hasindicated a complex channel to levee architecture(Coleman et al., 1998). Channel lls up to 30 m thickconsist of sharp-based, aggradational to ning-upward,thin-bedded to thick-bedded sandstone and interbed-ded thin siltstones (Rossen and Sickafoose, 1994). Ad-jacent to the channels (our proximal channel-leveeand overbank association; see Slatt et al. [1998], gure2) are strata with increasing and decreasing dip pat-terns that change away from the channel into moreconstant low-angle dips (our distal channel-levee andoverbank association). In the hydrocarbon zone, the Lsand is represented by a high to moderate amplitude,laterally extensive seismic response, which has a at,nonerosive base and displays lateral thinning awayfrom the interpreted central channel (Rossen andSickafoose, 1994). In wells, the levee is up to 50 m

thick, has moderate gamma-ray levels, and has a ser-rate log pattern that is aggradational to ning upward(Rossen and Sickafoose, 1994). Lithologically theselevee strata consist of thin alternating sandstone andsiltstone interbeds (typically Bouma Tb, Tc, and Te)(Rossen and Sickafoose, 1994). Net-to-gross decreasesaway from the channel.

We interpret this as the equivalent to our proximalchannel-levee and overbank association. Although rockproperties are good (core porosities 1532% and per-meabilities 201000 md), ow unit barriers preventgood communication and reduce well performance.These barriers to hydrocarbon ow could be caused bystratigraphic pinch-out of channel-levee and overbanksands (Clemenceau, 1995). Gas ow rates of approx-imately 100 MMCFGD and 9600 BCPD were ob-tained from proximal levee beds in the L sand (Slatt etal., 1998).

Mahogany Field, Gulf of MexicoThe P sand is the main reservoir unit in the Mahoganyeld. Although published details are sketchy, the Psand appears to have many sedimentary and petro-physical attributes comparable to the Mt. MessengerFormation. The upper part of the P sand comprises twomain lithofacies. Ripple-laminated sandstone and silt-stone (as thin as 5 mm) have porosities of 1828% andpermeabilities of 100500 md (Camp and McGuire,1997). Thicker bedded and coarser grained sandstonehave porosities up to 33% and permeabilities up to2500 md (Camp and McGuire, 1997). A 9 mthick


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Figure 15. Plan view model(A) for the depositional settingand stratal geometries of thePukearuhe Beach slope fanlithofacies. The diagram depictsa series of vertically stackedslope fan systems, each with(1) channel-ll, (2) proximalchannel-levee, and (3) distalchannel-levee associations. Incross section (B), slope fan ele-ments are vertically stacked assuccessively younger fan sys-tems are offset from previoussystems. Small enlargementsshow different sedimentologicfeatures in each association:thick siltstone or sandstonewithin large channel lls (cf.Figure 10); abundant channeli-zation, cut and ll and mud-draped scours, and Bouma tur-bidites in proximalchannel-levee association areas(cf. Figures. 2, 13, 14); and thinbeds of sandstone withinsiltstone-dominated packages ofthe distal channel-levee associa-tion (cf. Figure 9).

DOWNCURRENT

N

11

2

2

23

3

3

Proximal channel-levee association (near to feeder channels-cut and fill and mud-draped scours)

Channel-fill association(thick siltstone or sandstone deposits within large channels)

Proximal channel-levee association(away from feeder channels-Boumaturbidites characterized by climbing-ripple laminated Tc intervals

Distal channel-levee association(interbedded sandstone and siltstone;dominated by siltstone)

(A)

(B)

interval produced up to 3700 BOPD (Camp andMcGuire, 1997).

Implications for Petroleum Reservoir Quality andProduction Performance

Reservoirs within slope fan complexes of the type de-scribed here are notoriously difcult to model in termsof reservoir performance. In many reservoirs, perme-

ability is commonly the dominant control on reservoirquality and, ultimately, production efciency. We be-lieve, however, that in thin-bedded reservoirs as de-scribed here, characteristics such as bed-scale conti-nuity and connectivity probably are a greater factor indetermining the performance of a reservoir than is per-meability alone. Therefore, reservoir continuity andconnectivity at the subseismic scale need to be in-cluded in reservoir geologic and simulation models.


In a Miocene example from the Gulf of Mexico,Roberts and Compani (1996) indicate that detailed logcorrelation of channel-levee beds between closelyspaced wells is difcult or impossible for wells spacedas close as 90150 m. We suggest that this difculty isa likely occurrence in channel-levee and overbanksettings.

Mud drapes or erosional surfaces that cut out sandbeds, thinning of sand beds down levee anks, and theabundance of mud interbeds are all likely to reduceuid ow in such reservoirs. This is especially true forvertical uid ow. We suggest that in many cases poorcommunication exists between the channel associationand the adjacent levee and overbank strata because ofthe abundance of mud-draped scours along channelmargins. This tends to be supported by pressure datafrom inferred channel-levee and overbank reservoirsuccessions. For example, drillstem tests in the N1 in-terval of Green Canyon eld show strong transmissi-bility restrictions within 73 and 175 m from penetra-tion points in two wells. Rafalowski et al. (1994)attributed these restrictions to lateral offset of units,but it is also possible that they were caused by erosionalcutout of beds, of a type described previously for theMt. Messenger Formation. Another example is fromthe L sand reservoir interval in the Ram/Powell eld,where wells tests show that pressure transientestimated permeability is considerably less than core-derived permeability data. The lower reservoir per-meability, measured from the producing well, isthought to be due to a tortuous ow path through in-terbedded sandstone and siltstone that comprise thechannel-levee beds (Slatt et al., 1998).

Based on our outcrop and subsurface data, wewould predict that the best reservoir is probably notwithin the channel association, as these are commonlymud prone, but on the thin-bedded proximal and distalchannel-levee and overbank associations. In these set-tings, net sand is likely to be 50% or less, but the origi-nal depositional geometry can provide stratigraphictrapping on the upper levee anks, with hydrocarbonssealed by mud drapes on channel margins.

CONCLUSIONS

Combined outcrop and subsurface data indicate threefacies associations exist in the slope fan strata of theMt. Messenger Formation. These three associations are(1) channel ll (siltstone and interbedded sandstoneand siltstone), (2) proximal channel-levee and over-

bank units (alternating sandstone and siltstone ar-ranged in packages with opposing bedding attitudes),and (3) distal channel-levee and overbank units (pre-dominantly siltstone and thin interbedded ripple-laminated sandstone). Slope fan strata in other settingsmay show similar lithofacies associations. We predictthat the best reservoir will occur in the proximal anddistal channel-levee and overbank strata, rather than inthe more mud-prone channel lls themselves. We con-tend that erosional truncation of beds acts to reducecommunication between the channel ll and proximalchannel-levee and overbank strata, and this may be thecause for the poor pressure communication commonlynoted between these two zones in subsurface settings.

REFERENCES CITED

Bouma, A. H., and H. de V. Wickens, 1991, Permian passive marginsubmarine fan complex, Karoo Basin, South Africa: possiblemodel to Gulf of Mexico: Transactions of the Gulf Coast As-sociation of Geological Societies, v. 41, p. 3042.

Bouma, A. H., and H. de V. Wickens, 1994, Tangua Karoo, ancientanalog for ne-grained submarine fans, in P. Weimer, A. H.Bouma, and B. F. Perkins, eds., Submarine fans and turbiditesystems: Gulf Coast Section SEPM 15th Research Conference,p. 2334.

Browne, G. H., and R. M. Slatt, 1997, Thin-bedded slope fan(channel-levee) deposits from New Zealand: an outcrop analogfor reservoirs in the Gulf of Mexico: Gulf Coast Association ofGeological Societies Transactions, v. 47, p. 7586.

Browne, G. H., A. McAlpine, and P. R. King, 1996, An outcropstudy of bed thickness, continuity, and permeability in reservoirfacies of the Mt. Messenger Formation, north Taranaki: Pro-ceedings of the New Zealand Petroleum Exploration Confer-ence, p. 154163.

Browne, G. H., R. M. Slatt, and P. R. King, 2000, Contrasting stylesof basin-oor fan and slope fan deposition: Mount MessengerFormation, New Zealand, in A. H. Bouma and C. G. Stone,eds., Fine-grained Turbidite systems: AAPGMemoir 72/SEPMSpecial Publication 68, p. 143152.

Camp, W. K., and D. McGuire, 1997, Mahogany eld, a subsaltlegend: a tale of technology, timing, and tenacity, offshoreGulfof Mexico (abs.): AAPG Annual Convention, p. A17.

Carter, R. M., L. Carter, and B. Davy, 1994, Seismic stratigraphy ofthe Bounty Trough, south-west Pacic Ocean: Marine and Pe-troleum Geology, v. 11, p. 7993.

Chapin, M. A., P. Davies, J. L. Gibson, and H. S. Pettingill, 1994,Reservoir architecture of turbidite sheet sandstones in laterallyextensive outcrops, Ross Formation, western Ireland, in P.Wei-mer, A. H. Bouma, and B. F. Perkins, eds., Submarine fans andturbidite systems: Gulf Coast Section SEPM 15th Annual Re-search Conference, p. 5368.

Clemenceau, G. R., 1995, Ram/Powell eld: Viosca Knoll 912,deepwater Gulf of Mexico, in R. D. Winn and J. M. Armen-trout, eds., Turbidites and associated deep-water facies: SEPMCore Workshop 20, p. 95129.

Clemenceau, G. R., J. Colbert, and D. Edens, 2000, Production re-sults from levee-overbank turbidite sands at Ram/Powell eld,deepwater Gulf of Mexico: Gulf Coast Section SEPM 20thAn-nual Research Conference, p. 241251.


Coleman Jr., J. M., G. H. Browne, R. M. Slatt, and G. R. Clemen-ceau, 1998, Comparison of two turbidite intervals: TaranakiBasin (New Zealand) and Gulf of Mexico Basin (USA): GulfCoast Association of Geological Societies Transactions, v. 48,p. 535.

Cook, T. W., A. H. Bouma, M. A. Chapin, and H. Zhu, 1994, Faciesarchitecture and reservoir characterization of a submarine fanchannel complex, Jackfork formation, Arkansas, in P. Weimer,A. H. Bouma, and B. F. Perkins, eds., Submarine fans and tur-bidite systems: Gulf Coast Section SEPM 15th Annual Re-search Conference, p. 6981.

Cossey, S. P. J., 1994, Reservoir modeling of deep-water clastic se-quences: mesoscale architectural elements, aspect ratios, andproducibility, in P. Weimer, A. H. Bouma, and B. F. Perkins,eds., Submarine fans and turbidite systems: Gulf Coast Asso-ciation SEPM 15th Annual Research Conference, p. 8393.

Damuth, J. E., R. O. Kowsmann, R. D. Flood, R. H. Belderson, andM. A. Gorini, 1983, Age relationships of distributary channelson Amazon deep sea fan: implications for fan growth pattern:Geology, v. 11, p. 470473.

DeVries, M. B., and R. M. Lindholm, 1994, Internal architecture ofa channel-levee complex, Cerro Toro Formation, southernChile, in P. Weimer, A. H. Bouma, and B. F. Perkins, eds.,Submarine fans and turbidite systems: Gulf Coast SectionSEPM 15th Annual Research Conference, p. 105114.

Diridoni, J. L., 1996, Sequence stratigraphic framework of the Mio-cene Mt. Messenger Formation deep-water clastics, north Tar-anaki Basin, New Zealand: Masters dissertation, ColoradoSchool of Mines, Golden, Colorado, 165 p.

Flood, R. D., D. J. W. Piper, and Shipboard Scientic Party, 1995,Introduction, in R. D. Flood et al., eds., Proceedings of theOcean Drilling Program, initial report, v. 155: College Station,Texas, Ocean Drilling Program, p. 516.

Hansen, R. J., 1996, Stratigraphy, sedimentology, and paleomagne-tism of a late Miocene succession, eastern Taranaki Basin mar-gin: Masters dissertation, University of Waikato, Hamilton,New Zealand, 184 p.

Hiscott, R. N., C. Pirmez, and R. D. Flood, 1997,Amazon submarinefan drilling: a big step forward for deep-sea fan models: Geo-science Canada, v. 24, p. 1324.

Jordan, D. W., D. J. Schultz, and J. A. Cherng, 1994, Facies archi-tecture and reservoir quality of Miocene Mt. Messenger deep-water deposits, Taranaki Peninsula, New Zealand, in P. Wei-mer, A. H. Bouma, and B. F. Perkins, eds., Submarine fans andturbidite systems: Gulf Coast Section SEPM 15th Annual Re-search Conference, p. 151166.

Jordan, D. W., P. R. King, and G. H. Browne, 1995, Petrophysicaland textural characteristics of thin-bedded turbidite sands,Mio-cene Mt. Messenger Formation, Taranaki Peninsula, New Zea-land (abs.): AAPG International Conference, p. 34A.

King, P. R., and G. P. Thrasher, 1996, CretaceousCenozoic geologyand petroleum systems of the Taranaki Basin, New Zealand:Institute of Geological and Nuclear Sciences Monograph 13,243 p.

King, P. R., G. H. Scott, and P. R. Robinson, 1993, Description,correlation and depositional history of Miocene sediments out-cropping along the north Taranaki coast: Institute of Geologicaland Nuclear Sciences Monograph 5, 199 p.

King, P. R., G. H. Browne, and R. M. Slatt, 1994, Sequence archi-tecture of exposed late Miocene basin oor fan and channel-levee complexes (Mount Messenger Formation), Taranaki Ba-sin, New Zealand, in P. Weimer, A. H. Bouma, and B. F.Perkins, eds., Submarine fans and turbidite systems: Gulf CoastSection SEPM 15th Annual Research Conference, p. 177192.

Lindsay, S. A., 1996, Sedimentology of late Miocene siltstone bedsand sequence stratigraphic signicance, eastern margin, Tar-

anaki Basin: Masters dissertation, University ofWaikato,Ham-ilton, New Zealand, 233 p.

Manley, R., and D. W. Lewis, 1998, Ichnocenoses of the MountMessenger Formation, a Miocene submarine fan system, Tar-anaki Basin, New Zealand: New Zealand Journal of Geologyand Geophysics, v. 41, p. 1533.

Mutti, E., 1985, Turbidite systems and their relations to depositionalsequences, in G. G. Zuffa, ed., Provenance of arenites: NATO-Advanced Study Institute Series, p. 6593.

Mutti, E., and F. Ricci Lucchi, 1978, Turbidites of the northern Ap-ennines: Introduction to facies analysis: American GeologicalInstitute Reprint Series 3, International Geology Review, v. 20,p. 125126.

Rafalowski, J. W., B.W. Regal, D. L. Jordan, andD.O. Lucidi, 1994,Green Canyon Block 205 lithofacies, seismic facies, and reser-voir architecture, in P.Weimer, A. H. Bouma, and B. F. Perkins,eds., Submarine fans and turbidite systems: Gulf Coast SectionSEPM 15th Annual Research Conference, p. 293306.

Ricci Lucchi, F., 1984, The deep-sea fan deposits of the MioceneMarnoso-Arenacea Formation, Northern Apennines: Geo-Marine Letter, v. 3, p. 203210.

Roberts, M. T., and B. Compani, 1996, Miocene example of a me-andering submarine channel-levee system from 3-D seismic re-ection data, Gulf ofMexico Basin, in J. A. Pacht, R. E. Sherriff,and B. F. Perkins, eds., Stratigraphic analysis utilizing advancedgeophysical, wireline and borehole technology for petroleumexploration and production: Gulf Coast Section SEPM 16thAnnual Research Conference, p. 241254.

Rossen, C., and D. K. Sickafoose, 1994, 3-D seismic expression andarchitecture of deep-water reservoirs at Ram/Powell eld,Viosca Knoll Block 912, Gulf of Mexico, in P. Weimer, A. H.Bouma, and B. F. Perkins, eds., Submarine fans and turbiditesystems: Gulf Coast Section SEPM 15th Annual ResearchCon-ference, p. 309310.

Slatt, R. M., G. H. Browne, R. J. Davis, G. R. Clemenceau, J. R.Colbert, R. A. Young, H. Anxionnaz, and R. J. Spang, 1998,Outcropbehind outcrop characterization of thin-bedded tur-bidites for improved understanding of analog reservoirs: NewZealand and Gulf of Mexico: Society of Petroleum EngineersAnnual Technical Conference and Exhibition, SPE Paper49563, p. 845853.

Spang, R. J., R. M. Slatt, G. H. Browne, N. F. Hurley, E. T.Williams,R. J. Davis, G. R. Kear, and L. S. Foulk, 1997, Fullbore For-mation Micro Imager logs for evaluating stratigraphic featuresand key surfaces in thin-bedded turbidite successions: GulfCoast Association of Geological Societies Transactions, v. 47,p. 643645.

Swart, R., 1992, The sedimentology of the Zerrissene turbidite sys-tem, Damaara orogen, Namibia: Geological Survey of NamibiaMemoir 13, 54 p.

Van Wagoner, J. C., H. W. Posamentier, R. M. Mitchum, P. R. Vail,J. F. Sarg, T. S. Loutit, and J. Hardenbol, 1988, An overviewof the fundamentals of sequence stratigraphy and key deni-tions, in C. K. Wilgus, B. S. Hastings, C. G. St. C. Kendall,H. W. Posamentier, C. A. Ross, and J. C. Van Wagoner, eds.,Sea level changes: an integrated approach: SEPM Special Pub-lication 42, p. 3945.

Walker, R. G., 1985, Mudstones and thin-bedded turbidites associ-ated with the Upper CretaceousWheelerGorge conglomerates,California: a possible channel-levee complex: Journal of Sedi-mentary Petrology, v. 55, p. 279290.

Zelt, F. B., and C. Rossen, 1995, Geometry and continuity of deep-water sandstones and siltstone, Brushy Canyon Formation (Per-mian) Delaware Mountains, in K. T. Pickering, R. N. Hiscott,N. H. Kenyon, F. Ricci Lucchi, and R. Smith, eds., Atlas ofarchitectural styles in turbidite systems: London, Chapman andHall, p. 167181.

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Browne and Slatt 2002.pdf