Figure 1. Proposed drillingsites in antarctic waters;only areas of primary in-terest are shown for the

975 season.

Extensive drilling program planned for Glomar Challengerin antarctic waters

As a result of the enthusiastic response of theoceanographic community, plans have now beenformulated to conduct deep-sea drilling in antarcticwaters. A program of drilling in high southernlatitudes (fig. 1) has been planned by the Deep SeaDrilling Project of the Scripps Institution of Ocean-ography in conjunction with the Joint OceanographicInstitutions for Deep Earth Sampling (JOIDES)Planning Committee, the JOIDES Antarctic AdvisoryPanel, the National Science Foundation's Offices ofPolar Programs and National Centers and Facilities,and Global Marine, Inc. At least five 56-day cruisesof Glomar Challenger, spanning three austral sum-mers, are proposed.

The drilling ship Glomar Challenger (cover;

DENNIS E. HAYES

Lamont-Doherty Geological Observatory

and

N. TERENCE EDGAR

Scripps Institution of Oceanography

January—February 1972

fig. 2) is essentially a standard drilling ship modifiedto meet the requirements of the Deep Sea DrillingProject. The current plans call for a ship capableof drilling and coring in up to 6700 meters of waterand to at least 1000 meters below the ocean floor.The vessel is equipped with a dynamic positioningsystem (fig. 3) which enables her to maintain stationin oceanic depths, usually to within a 30-meter radiusof a point on the ocean surface above a referenceacoustic beacon on the sea floor. Experience hasdemonstrated that station can be maintained in5-meter seas with 30-40 knot winds, but the limitsof operation cannot be expressed solely in scalarvalues; differences in relative direction of swell,current, and wind also bear heavily on operationallimitations. Drilling cannot be maintained while theship is experiencing rolls much greater than 5 de-grees from the vertical or 3 degrees pitch, but thishas not proved to be a severe limitation owing to theinherent stability of the craft and the use of anti-rollstabilizers.

Positioning beacons have a typical life span of5-7 days, but it can be increased by adding batterypacks. For extended periods on station, a secondbeacon, emitting a different frequency, can be utilizedwhen the first one expires.

A reentry system has been developed for drillinginto hard rock where drill bit replacement may be re-quired. The system permits the drill pipe to belowered into the same hole on the ocean floor in upto 6000 meters of water. Reentry is not normallyrequired when drilling in soft oceanic sediments,but it is a valuable capability when drilling in igneousrock beneath the sediment cover.

Cores are recovered in a 9-meter core barrel by

the wire line method. In soft sediments at oceanicdepths, about 100 meters of sediment can be coredper day. Recovery averages 50-75% of the totalsection cored, and consistent 100 17o recovery is rarelyachieved. In hard limestone and cherts, core recoveryis rarely more than 25%. Sand and gravel are verydifficult to recover, as the drill pipe frequently be-comes stuck in the hole—a cause for concern whendrilling in glacial deposits.

Marine geophysical reconnaissance south of 35°S.is relatively good, except for a sector between 30°W.and 90°E. that encompasses the southeast Atlanticand southwest Indian Oceans. In the area wheregood geophysical data are available, a number ofspecific as well as general problems are now welldefined. In order to best complement the existingsurvey data, the first antarctic drilling season, whichwill commence in December 1972, will concentrateon problems in the southeast Indian and southwestPacific Oceans. The second antarctic drilling seasonbegins in January 1974, when holes will be drilled inthe southeast Pacific, including the BellingshausenBasin, the Scotia Sea, and the Weddell Sea.

The third drilling season is to be devoted to study-ing the southeast Atlantic and the southwest andsouth central Indian Ocean. Plans for the thirdseason's drilling are tentative as regards specificdrilling objectives. It is scheduled for February 1975,which allows time for additional reconnaissance sur-veying and data analysis. The Kerguelen Plateau,located near 70°E. longitude, is the primary area ofinterest, but its remote location may require somemodification to the standard 2-month leg format inorder to accommodate proposed drilling sites on theplateau. Because of these difficulties, the ship's de-

Figure 2. Glomar Chal-lenger. The0,500-tondrilling ship has a lengthof 400 feet, beam of 65feet, and loaded draftof 20 feet. Amidships isthe 142-foot derrick. For-ward of the derrick isthe automatic drill piperacker containing 7,000meters of 14-cm drill

pipe.

;

ANTARCTIC JOURNAL

tailed schedule for 1975 will be reevaluated after theproposed 36-month Deep Sea Drilling Project exten-sion is well under way.

Several principles of operation have been followedin developing the proposed plan:

(1) The Glomar Challenger will not proceed intoareas of hazardous ice or where icebreaker supportis necessary to sustain operation.

(2) To avoid possible damage to the ship'sthrusters, the ship will avoid drilling holes in areasof brash ice cover.

(3) The Glomar Challenger should be able tomaintain station position in relatively shallow water,thus allowing for drilling on the depressed continentalshelf (about 500 meters) off Antarctica.

(4) Realizing the possibility of adverse weatherconditions, especially north of the Antarctic Converg-ence, drill sites have been selected to allow for flexi-bility in scheduling so that lost time due to weatheris minimized.

A number of scientific problems that were pro-posed by Ewing and Hayes (1970) as suitable forexamination through antarctic drilling have servedas a valuable guide in formalizing the objectives ofthe antarctic deep sea drilling program. The generalobjectives include examination of:

(1) The chronology of Gondwanaland separationand areas of possible old sea floor. Evidence gatheredso far from the oceans indicates that the sea-floorspreading/ continental drift system appears to haveeffectively renewed the ocean floor after the breakupof the single continent of Gondwanaland. The oldestrocks recovered from the ocean are more than anorder of magnitude younger than those of thecontinents. However, from models reconstructingGondwanaland, it is apparent that areas adjoiningparts of the antarctic coastline may consist of pre-served ancient oceanic crust that existed prior tocontinental breakup. Sites treating these problemsrequire drilling into layer 2 basalt (of the oceaniccrust) and dating these crystalline rocks eitherthrough the radiometric technique or by paleontologi-cally dating the sediments resting directly on thebasalt.

(2) The volcanic, glacial, and climatic history ofAntarctica, particularly regions near the coast. Oneprimary objective is to compare the historic condi-tions of the major antarctic sectors, with the emphasisgiven to contrasting the geologic history of relativelyold, stable East Antarctica and young, tectonicallyactive West Antarctica.

(3) The biostratigraphy and sediment distributionin the Antarctic. A proper evaluation of the role ofthe Antarctic Continent as a sediment source, anddetermination of the onset of continental glaciation,are important aspects of this category of study. Studiesof sediment distribution will help define the history

of Antarctic Bottom Water formation, which ibelieved to have an influence on the deep circulationof all the major ocean basins.

(4) The tectonic history of the antarctic margin,subantarctic ridges, and islands. Primary target areasinclude the Scotia Ridge and Arc, the MacquarieRidge complex, the Balleny Ridge, and the KerguelenPlateau. Investigations of tectonic problems throughdeep drilling normally require a series of comple-inentary holes. In most cases these holes can also belocated to investigate problems other than those ofa tectonic nature.

The sites proposed by the JOIDES AntarcticAdvisory Panel were chosen to investigate multipleobjectives. Because so little is known about thePaleocene and older history of Antarctica and ad-jacent ocean environments, five sections, each com-prised of a hole on the continental shelf, the con-tinental rise, and the deep basin floor, are beingplanned as a general drilling reconnaissance phase.The sections will be located near longitudes 105°E.,165 0 W. 5 100 0 W. 1 15 0 W., and 30 0 E. While the re-sults obtained at these sites should prove valuable in

Figure 3. Features of the dynamic positioning system that keepsGlomar Challenger on station while drilling. Not to scale.

January—February 1972 3

themselves, their greatest value may lie in the oppor-tunity they provide to compare data from differentsections.

The Ross Sea shelf is an area of particular interestin that the three holes proposed for that area aredesigned to complement the Ross Ice Shelf drillingproject, which provides for several holes through theRoss Ice Shelf. The scientific program of the projectis multidisciplinary in nature (Zumberge, 1971), butthe pilot hole planned for late 1972 will not attemptto sample the sediments on the floor of the shelf belowthe ice. Drilling operations also are being proposedfor selected sites in the dry valleys region (see fig. 4).It is our hope that the results of the three Ross Seashelf holes of the Deep Sea Drilling Project, in con-junction with the Ross Ice Shelf Project and the DryValley Drilling Project, can be used to reconstruct thearea's glacial and geologic history, drainage patternand sedimentation, and the cause and nature of thedepressed continental shelf of the Ross Sea area.

No specific coordinates have been designated thatestablish the domain of the JOIDES Antarctic Ad-visory Panel; however, holes have been proposed bythis panel for latitudes as low as 35°S. Through thefirst 40 months of the Deep Sea Drilling Project, only12 holes have been drilled south of 25°S., and onlyone exists south of 35°S. The JOIDES AntarcticAdvisory Panel is in close communication with the

Figure 4. Proposed deep drilling sites inRoss Sea area. DSDP: Deep Sea Drill-ing Project. DVDP: Dry Valley DrillingProject. RISP: Ross Ice Shelf Project.Selected isobaths are shown in4meters.

RISPAHOLE

oss/CE S//ELF

VDP•Z;4

other JOIDES advisory panels, and it should bestressed that there are no sites whose positions havebeen categorically fixed.

Many of the sites will be surveyed prior to drillingto pinpoint the optimum location for achieving theplanned objectives. The survey data are also of greatbenefit to the scientists for making interpretations ofthe drilling results on a local and regional basis.Approximately 90 to 100 days of Eltanin ship timehave been allocated for detailed surveying in supportof deep drilling in the southwest Pacific, the RossSea, and the southeast Indian Ocean. R/V Robert D.Conrad of Lamont-Doherty Geological Observatoryis presently surveying the southeast Pacific, and. aBritish team from the University of Birmingham isaboard the RRS Shackleton surveying in the ScotiaSea. The proposed antarctic drilling sites will becarefully reevaluated in the summer of 1972, whenthe data from these extensive surveys have beenanalyzed.

Members of the Joint Oceanographic Institutionsfor Deep Earth Sampling (JOIDES) are: Lamont-Doherty Geological Observatory of Columbia Uni-versity, Scripps Institution of Oceanography of theUniversity of California at San Diego, RosenstielSchool of Marine and Atmospheric Science of theUniversity of Miami, Woods Hole OceanographicInstitution, and the University of Washington.

JOIDES Antarctic Advisory Panel members in-clude: Dennis Hayes, Chairman; Robert H. Rutford,University of South Dakota; Campbell Craddock,University of Wisconsin; James P. Kennett, Universityof Rhode Island; James R. Heirtzler, Woods HoleOceanographic Institution; James H. Zumberge, Uni-versity of Nebraska; Ian W. D. Dalziel, Lamont-Doherty Geological Observatory; and David W.Scholl, U.S. Geological Survey.

References

Ewing, M., and D. Hayes. 1970. Deep-sea drilling in antarcticwaters. Geotimes, 5(9) : 15-16.

Zumberge, J . 1971. Ross Ice Shelf Project. Antarctic Journalof the U.S., VI (6) : 258-263.

Inquiries regarding participationon cruises of the Glomar Challengershould be directed to N. TerenceEdgar, Chief Scientist of the DeepSea Drilling Project, Scripps Insti-tution of Oceanography, P.O. Box109, La Jolla, California 92037;those pertaining to drill sites of theantarctic program should be di-rected to Dennis E. Hayes, Chair-man of the JOIDES Antarctic Ad-visory Panel, Lamont-Doherty Geo-logical Observatory, Palisades,New York 10964.

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