175°W. meridian are truncated by an erosion surfacethat exposes about 2,500 meters of section. Hence acomplete sample of the stratigraphy from basement toquite recent sediments is available in the outcrops.

Sonobuoy data reveal an abrupt 2-kilometer thick-ening of sediments, probably fault-controlled, in theregion of Pennell Bank. Relatively tight fold struc-tures (of limited extent) occur within north-southtrending basins that are unconformable on the oldershelf sediments. A narrow gravity high projects fromthe ice shelf northward approximately along the175°E. meridian. It is associated with a thickeningof the sediment cover to the west of a possible fault.

Track of Eltanin Cruise 52.

The Lamont-Doherty group occupied 10 hydrostations and three bottom current meter stations onthe shelf; the latter yielded about 18 days of bottomcurrent recordings. The hydro work was undertakento better determine the outflow of cold bottom waterfrom the Ross Sea shelf. Three camera/ nephelometerstations also were completed on the shelf by the hydrogroup.

A Florida State University group took 12 pistoncores during this cruise; all but three on the Campbellplateau were obtained from the Ross Sea shelf andrise.

A free-fall biological sampling net was deployed bypersons from the University of Canterbury andDePaul University on a noninterefering basis duringthis cruise. Fifty-four casts were completed andanalyzed aboard to measure biomass and metabolism.

Robert D. Conrad Cruise 15,Valparafso to Punta Arenas

STEPHEN L. EITTREIM

Lamont-Doherty Geological ObservatoryColumbia University

This 26-day leg of Robert D. Conrad, December 5to 31, 1971, was designed around a limited number ofprincipal objectives. Several crossings of the Peru-Chile trench were planned with emphasis on the struc-ture and composition of the landward wall. Two sur-veys were to be made over sites selected for drilling byGlomar Challenger in the southwest Drake Passage.Patterns of magnetic anomalies and fracture zonemorphology were to be investigated in the westernDrake Passage.

The standard underway measurements aboard Con-rad included seismic profiling, gravity, magnetics, and12- and 3.5-kiloHertz echo sounding. Stations, whichwere taken roughly daily, included a piston core, bot-tom photographrs, a vertical nephelometer profile, anda secchi disk measurement.

A few highlights of the collected data are the follow-ing: On the first crossing of the Peru-Chile trenchsouthwest of Valparaiso, the basement layer on theseismic profiler displayed a continuous shallow diplandward extending at least 15 kilometers eastward ofthe trench axis. Sediments about 2 seconds thick com-prise the landward wall overlying the basement. Thissediment displays no coherent internal reflections.

In the southwest Drake Passage an axis of symmetryin the magnetic anomaly pattern was found corre-sponding to the crest of a sediment-free ridge (fig.).The Conrad 15 track was planned to be roughly par-

126 ANTARCTIC JOURNAL

graphic feature of the Drake Passage, connecting thesouthernmost spur of the South American continentalshelf to Elephant Island of the South Scotia Ridge.

The two site surveys conducted near the antarcticcontinental margin established the existence of con-sistent magnetic patterns over the survey areas whoselineations trend northeast-southwest. The easternmostshowed a repetition of the anomalies associated withthe southeast flank of the spreading center mentionedabove. The westernmost survey recorded anomalies ofentirely different character, apparently associated witholder crust, as indicated by a sediment thickness ofabout 1 second.

Reference

Barker, P. F. 1970. Plate tectonics in the Scotia Searegion. Nature, 228: 1293-1296.

Other research projectsactive during the 1971-1972 summerTemperature regulation in the newborn Weddell

seal. University of California, San Diego. Principalinvestigator: Robert W. Eisner.

Chlorinated hydrocarbons: patterns and effectsupon the reproductive capacity of antarctic pelagicsea birds. University of California, Berkeley. Princi-pal investigator: Harold S. Wolcott.

Thermal pendulum probe of ice cap at South PoleStation. U.S. Army Cold Regions Research and En-gineering Laboratory. Principal investigator: LyleW. Hansen.

Valparoiso

45+,

(

f f South Americo

55/80

/ 8 I

Track of Robert D. Conrad Cruise 15, with selected basementtopography and magnetic anomalies.

ailel to the fracture zones postulated by Barker (1970)in the Drake Passage. This track plan resulted in anapparently unbroken record of the magnetic anomalypatterns west of the Shackleton fracture zone, and itgenerally confirms the pattern postulated by Barker onthe basis of anomalies observed only on the southeastlimb of the spreading center. The same anomaly pat-tern associated with the southeast flank was observedon the track just west of the Shackleton fracture zone,but the turn to the north toward Punta Arenas wasmade before reaching the crestal anomalies.

Three crossings were made of the Shackleton frac-ture zone, confirming its existence as a major topo-

Proceedings of conservationcolloquium are published

Proceedings of the Colloquium on ConservationProblems in Antarctica, edited by Dr. Bruce C. Par-ker, has been published. The 376-page, cloth-boundbook contains the 19 papers and the four work groupsummaries that were presented at the colloquium,which took place at Virginia Polytechnic Institute andState University, September 9-11, 1971. Appendixescontain such documents as the Antarctic Treaty andthe complete text of the February 1972 Conventionfor the Conservation of Antarctic Seals.

The book is available from Dr. Bruce C. Parker,Department of Biology, Virginia Polytechnic Instituteand State University, Blacksburg, Virginia 24061. Theprice is $10. The colloquium was supported througha National Science Foundation grant.

July-August 1972 127