Table 1. Diatom populations, by depth, in sediment fromsite J-9Diatom biostratigraphy in

sediment cores from RISP site J-9

HOWARD THOMAS BRADY

School of Biological SciencesMacquarie University

North Ryde, New South Wales, Australia

In December 1978, 48 gravity cores were obtained insea floor sediments at the Ross Ice Shelf Project (R!SP)site J-9. Further diatom analysis confirms this author'searlier opinion that the sediment cores recovered areMiddle Miocene in age (Brady and Martin, 1979). Sta-tistical population studies have been completed on core9 (1978), which suggest that there is no floral differencebetween the upper light olive-gray diatomaceous sandymud (up to 20 centimeters thick) and the lower graydiatomaceous sandy mud (at least 105 centimeters thick)(Webb, Ronan, and Lipps, 1979). Diatom populationsdo not alter significantly across this boundary (see table).The only change occurs in the upper 5 centimeters,where the diatom fossils are extremely fragmented. Inthis zone, a fauna of Pleistocene benthic foraminiferahas been living on the fossil sediment (Lipps, Ronan,and Delaca, 1979). The high fragmentation in this upperlayer may be due to biogenic factors, but this problemhas not been resolved.

It was clear that, during coring operations, mud felloff the gravity corer and remained in suspension in theocean. At least one of the diatoms reported from thewater column by Azam et al. (1979) is a common fossilin the sediment (Trinacria sp.). However, it should notbe assumed that all diatoms recovered from the watercolumn have originated from the coring operation; a!-though no Amphipora, Pinnularia, or Navicula specieswere recovered from the bottom sediments, they havebeen reported from the water column.

Given that water pumped from the freshwater columnin the ice access hole and from the water column beneath

Depth: 0 5 10 15 20 25 50 60 125(in centimeters)

Chaetoceros spores1 8 5 6 4 5 3 2 7Denticula hustedtii19 1116

Denticuia lauta .3.3Nitzschia grossepunctata.3 .3.3 1Nitzschia truncata 5 4 3 57 2Paralia sulcata8 28 31 23 30 32 28 28 30

Rhaphoneis spp. 1 2 211Rhizosolenia hebetata8 7 12 11 7 10 5 8 7

Stephanopyxisspp.1 8 6 2 9 5 11 6 13Synedra spp. 4 3 4 6 3 4 2 4 4

Thaiassiosira fraga8 4 3 4 7 3 8 7Thalassiosira aft. gravida5 10 4 2 4 6 5 8

T. spinosa var. aspinosa1 3 1 1 5Trinacria spp. 2 3 1 3 4 3 1 2 4

the shelf in December 1978 yielded many of the diatomfossils present in the sediments, some water samplingshould be performed in future RISP access holes priorto any bottom grab or gravity sampling.

This research has been supported by the National Sci-ence Foundation grant DPP 74-22894 supervised by Pe-ter Noel Webb.

References

Azam, F., J . R. Beers, L. Campbell, A. F. Carlucci, 0. Holm-Hansen, F. M. H. Reid, and D. M. Karl. 1979. Occurrenceand metabolic activity of organisms under the Ross IceShelf, Antarctica, at Station J.9. Science, 203: 451-53.

Brady, H. T., and H. Martin. Ross Sea region in the MiddlMiocene: A glimpse into the past. Science, 203: 437-38.

Lipps, J . H., T. E. Ronan, and T. E. Delaca. 1979. Life belosthe Ross Ice Shelf, Antarctica. Science, 203: 447-49.

Webb, P. N., T. F. Ronan, and J . H. Lipps. 1979. Miocencglaciomarine sediments from beneath the southern Ross IaShelf. Science, 203(4379): 435-37.

Sediment coring at RISP site J-9

P. N. WEBB

Department of GeologyNorthern Illinois University

De Kalb, Illinois 60115

Forty-seven cores of bottom sediment were collectedat RISP site J-9 during the period between 8 December

and 28 December 1978. These cores provide bottommaterial in addition to that collected about 350 metersfarther south during the 1977-78 season (Webb, 1978;Webb et al., 1979). During the 1977-78 season, we re-sieved eleven cores with a diameter of 4 or 5 centime-ters. The longest individual core was 102 centimeters,and the aggregate length for all eleven cores amountedto about 6 meters. In our 1978-79 operations, in aneffort to increase bottom penetration, we used newwinch and coring equipment, including a Gearhart-Owen SUA 800 winch, a Benthos model 2171 corer (3-meter barrel length), and an Ocean Seismic survey cores(5-meter barrel length). The forty-seven cores obtainedhave an aggregate length of 31.05 meters (101.87 feet)

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The longest core was 125 centimeters and the shortestwas 16 centimeters. Most of the cores were taken withthe heavier Ocean Seismic corer, and this device pro-vided cores with a diameter of 8 centimeters. The Ben-thos corer provided cores of about 6.7 centimeters.

Bottom penetration was disappointing. Despite ex-perimentation in dropping procedures, the very firmsediments just below the mudline could not be pene-trated to any significant depth. Onsite inspection of corematerial suggests that coring-related deformation ofthese firm sediments is minor. However, investigatorsinterested in core tops may find the companion sphinc-ter samples less disturbed. Gravity core tops have defi-nitely been subject to washout and other disturbances.

Detailed core logs and preliminary results are pre-sented in RIS? Technical Report no. 79-1 (Webb, 1979).The stratigraphy, sediments, and micropaleontology areidentical to those observed in cores retrieved during the1977-78 season. Brady (in press) reports mid-Miocenediatom floras throughout the 1978-79 cores.

All 1978-79 cores are deposited at the Antarctic Ma-rine Geology Research Facility and Core Library (Flor-ida State University).

The principal investigator was assisted in the field byHoward Brady (Macquarie University, Australia) and byMark Leckie and Richard White (both from NorthernIllinois University). This research effort has been sup-ported by National Science Foundation grant opp 76-20657.

References

Brady, H. T. 1979. Diatom biostratigraphy in sediment coresfrom beneath the Ross Shelf at RI5P site J-9. Antarctic Journalof the United States (this issue).

Webb, P. N. 1978. Initial Report on Geological Materials collectedat RI5P Site J9, 1977-78. RISP Technical Report, no. 78-1.

Webb, P. N. 1979. Initial Report on Geological Materials collectedat RISP Site J9, 1978-79. RI5P Technical Report, no. 79-1.

Webb, P. N., T. E. Ronan, J. H. Lipps, and T. E. Delaca. 1979.Miocene glaciomarine sediments from beneath the Ross IceShelf, Antarctica. Science, 203(4379): 435-37.

Paleoclimatic analysis of RossSea and dry valleys area

sediments

THOMAS B. KELLOGG and DAVIDA E. KELLOGG

Institute for Quaternary Studies and Department of GeologicalSciences

University of Maine at OronoOrono, Maine 04469

As part of our continuing study of Ross Sea sedimentsand their climatic history, we spent the period from 6November to 12 December 1978 collecting samples inthe dry valleys area and on the McMurdo Ice Shelf.

We collected samples of macrofossils, microfossils,sediment, and ice from 67 sites on the McMurdo IceShelf (southern McMurdo Sound) to supplement a sim-ilar collection we obtained during the 1976-77 field sea-son. Minze Stuiver (University of Washington) is deter-mining radiocarbon dates for the macrofossils andmaking oxygen isotope analyses of the ice samples. Weare making sedimentologic and microfossil analyses.This work will yield information on the paleo-oceano-graphic and climatic history of this portion of the RossIce Shelf (Kellogg et al., 1977).

Ice samples analyzed to date show that most of theMcMurdo Ice Shelf consists of frozen sea water (Stuiveret al., in prep.). The radiocarbon analyses show pro-gressively older ages toward the north from the northend of Black Island. Thus, the prominent dirt band thatextends northward from Black Island to the ice shelf

margin is expected to provide a continuous record ofoceanographic changes in McMurdo Sound since Un-grounding of this portion of the late Wisconsin Ross Seaice sheet.

An extensive suite of samples was collected fromperched deltas in Salmon Valley, near Cape Chocolate.We had studied similar perched deltas in Taylor Valley(D. Kellogg et al., in press) and concluded that the dia-toms present were nonmarine. This supported the hy-pothesis that a late Wisconsin lobe of grounded ice hadblocked the mouth of Taylor Valley.

Upon studying samples from Salmon Valley, Miagkovet al. (1976) concluded that the Salmon Valley deltascontain marine diatoms thereby indicating a history ofextensive eustatic sea level change in the McMurdoSound region. However, we suspect that Miagkov et al.incorrectly identified the diatoms, because Taylor andSalmon valleys should have similar histories. Our sam -pling is designed to provide data that will either supportor refute their contention. Samples of algae from theSalmon Valley deltas will be radiocarbon dated, and wewill continue our study of diatoms in these samples.

While we were in the field, we also collected samplesof uplifted marine material from separate locations inthe McMurdo Sound region and dry valleys area. Thelocations included the PectenlProspect Formation ofcentral Wright Valley, Cape Bird, White Island, theStranded Moraines, and Minna Bluff.

These samples will be studied to aid in our interpre-tation of the late Quaternary history of the region andto assist in our efforts to correlate the marine paleocli-matic record with the glacial stratigraphy of the dry val-leys area.

Laboratory work this past year was concentrated onstudies of diatoms in the Ross Ice Shelf Project (RIsP)cores from site J-9, diatoms in perched deltas in Taylor

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