Fine-fraction (<63 µm) grain-size analyses of 530 samples from Holes 1095A, 1095B, and 1095D allow assessment of the downhole grain-size distribution at Drift 7. A variety of data processing methods, statistical treatment, and display techniques were used to describe this data set. The downhole fine-fraction grain-size distribution documents significant variations in the average grain-size composition and its cyclic pattern, revealed in five prominent intervals: (1) between 0 and 40 meters composite depth (mcd) (0 and 1.3 Ma), (2) between 40 and 80 mcd (1.3 and 2.4 Ma), (3) between 80 and 220 mcd (2.4 and 6 Ma), (4) between 220 and 360 mcd, and (5) below 360 mcd (prior to 8.1 Ma).
In an approach designed to characterize depositional processes at Drift 7, we used statistical parameters determined by the method of moments for the sortable silt fraction to distinguish groups in the grain-size data set. We found three distinct grain-size populations and used these for a tentative environmental interpretation. Population 1 is related to a process in which glacially eroded shelf material was redeposited by turbidites with an ice-rafted debris influence. Population 2 is composed of interglacial turbidites. Population 3 is connected to depositional sequence tops linked to bioturbated sections that, in turn, are influenced by contourite currents and pelagic background sedimentation.
1Moerz, T., and Wolf-Welling, T.C.W., 2001. Data report: Fine-fraction grain-size distribution data and their statistical treatment and relation to processes, Site 1095 (ODP Leg 178, western Antarctic Peninsula). In Barker, P.F., Camerlenghi, A., Acton, G.D., and Ramsay, A.T.S. (Eds.), Proc. ODP, Sci. Results, 178 [Online]. Available from World Wide Web: <http://www-odp.tamu.edu/publications/178_SR/chap_24/chap_24.htm>. [Cited YYYY-MM-DD]
2GEOMAR Research Center for Marine Geoscience, Wischhofstrasse 1-3, C4, 24148 Kiel, Federal Republic of Germany. tmoerz@geomar.de
3Institute for Geosciences, Christian-Albrechts University Kiel, Olshausenstrasse 40, 24118 Kiel, Federal Republic of Germany.
Initial
receipt: 16 April 2001
Acceptance: 8 August 2001
Web publication: 29 November 2001
Ms 178SR-234