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Paleomagnetic Investigations in Marie Byrd Land

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Paleomagnetic Investigations in Marie Byrd Land ing one of three agar media, and the fourth was pre- western flank of the Ames Range. In addition, sam- served in CRAF fixative. Samples of soil, as well as ples were taken from Coleman Nunatak, providing a of obvious algal mats, were placed on culture media. link-up with the termination point of the studies con- All of the living cultures were shipped frozen and ducted last season. The specimens collected in these are now growing at Ohio State University in a con- areas appear to be basalts and andesites. trolled-environment chamber at 4°C. The Executive Committee Range yielded oriented Cultures prepared with material from all algal samples of volcanic lavas and tuffs from Whitney sampling localities contain specimens of chiorococ- Peak, Mounts Hampton, Waesche, and Cumming, calean algae. Prasiola crispa was collected at both and a sequence of progressively older rock at Mount Mathewson Point and at Jeffrey Head . Chlainy- Sidley. Additional samples were collected at Benes domonas sp. was collected only at the latter site. Peak and Mount Galla on the USAS Escarpment Cyanophyta, the most ubiquitous of antarctic algae, north of the Executive Committee Range. were present in samples from only 6 of the 10 collec- The second base camp was located near Toney tion sites. Samples from Mount Murphy were unique Mountain on the Bakutis Coast. Oriented samples in that they contained large numbers of filamentous were taken from basalts and tuffs on Spitz Ridge of and flagellated Chrysophyte cells. Toney Mountain, Turtle Peak at Mount Murphy, Owing to a malfunctioning telethermometer, tem- at Boyd Ridge in the Crary Mountains, and at sev- peratures were measured only in mid-November and eral sites west of Morrison Bluff in the Kohler early January. The measured maximum differential Range. Samples of plutonic rocks and associated dikes between the temperature of the air and of rocks upon were collected at Early Bluff, Mount Isherwood, which lichens were growing was 27.5°C. (air, and Mount Bray in the Kohler Range; at Hunt Bluff —16°C.; rock, + 11.5°C.) at 1930 local time on and Jeffrey Head on the Bear Peninsula; and at November 16. The maximum water temperature Siglin Rocks on the Martin Peninsula. measured was + 5.0°C. in a pond near Turtle Peak Because a large percentage of the oriented samples on January 6. The air temperature was also + 5.0°C. collected are basic volcanics, it is expected that the at that time. paleomagnetic data for them will be reliable and thus The animal life observed was limited to snow yield valuable information about the relationship of petrels at eight locations and Adélie penguins at East and West Antarctica. Some preliminary sugges- Mathewson Point. Although a concerted effort was tions as to this relationship have been made by C. K. made to collect arthropods by means of Berlese fun- Scharnberger and I. Hsu on the basis of a study of nels, none were found. plutonic and basaltic dike rocks collected during the 1966-1967 field season along the Saunders, Ruppert, and Hobbs Coasts. Unofficial name. Based on samples of basaltic rocks obtained at four sites, the mean south virtual geomagnetic pole (VGP) is at 62°S. 64°E. These results are considered to Paleomagnetic Investigations in be very reliable because of the high susceptibilities and strong remanence of the samples. The granitic Marie Byrd Land rocks, on the other hand, generally have low suscep- tibilities and weak remanence. A gneissic granite from LeROY SCHARON and THOMAS EARLY the Fosdick Mountains indicates that the south VGP is at 28°S. 140°W., which is about the same longi- Department of Earth Sciences tude but a lower latitude than the average position of Washington University (St. Louis) Jurassic poles for East Antarctica (53°S. 139°W.). An adamellite from the Clark Mountains indicated a In a continuation of the project begun last year in VGP at 22 0S. 1060 E., which is quite anomalous; the Marie Byrd Land by Washington University, rock result is doubtful, however, owing to the very weak samples for paleomagnetic studies were collected dur- intensity of magnetization. Additional measurements ing the 1967-1968 austral summer. Ninety-eight ori- of plutonic rocks will be carried out with more sensi- ented specimens were collected, from which approxi- tive instruments. mately 500 individual cores will be obtained for Our preliminary results indicate that further studies paleomagnetic measurements. must be made in order to fully elucidate the tectonic In the region of the first base camp on the Hobbs history of West Antarctica. Coast, samples were collected at Koerner Bluff, Mount Moulton, and Brandenberger Bluff in the Flood Range, as well as at numerous sites along the Unofficial name. 92 ANTARCTIC JOURNAL.
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