Sediment properties of drift deposits and their influence on seismic facies - an example from the Antarctic Peninsula continental margin


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chillenbrand [ at ] awi-bremerhaven.de

Abstract

During the last decade the Pacific margin of the Antarctic Peninsula was the target area of high-resolution multichannel reflection seismic profiling, bathymetric mapping, shallow gravity and piston coring as well as deep-sea drilling carried out in the frame of Ocean Drilling Program (ODP) Leg 178. The results of this unique data set of multi-disciplinary investigations revealed the existence of eight, huge, asymmetric sediment mounds separated by erosional channels on the continental rise. The recovered sedimentary sequences predominantly represent a mixture of fine-grained lithogenic particles and remains of biosiliceous microfossil tests, whereas calcareous components only occur in some individual layers. The mounds are interpreted as sedimentary drifts with the muddy detritus primarily supplied by turbidity currents, which travelled down the channels during late Cenozoic glacial periods, and re-deposited by a SW-ward flowing, near-bottom contour current. A detailed seismostratigraphic model was established distinguishing different phases of drift formation (pre-Drift, Drift Growth, and Drift Maintenance stage).The project ANTDRIFT aims to construct a 3-D framework of physical and sedimentological input parameters for a numerical forward model simulating the formation and evolution of the best investigated Drift 7. In order to identify the contribution of the different processes of sediment supply, transport, and (re-)deposition, especially the role of alongslope versus downslope transport, in building-up and shaping Drift 7 during the Drift Growth and Drift Maintenance stages the seismostratigraphic units of the reflection profiles are compared with the physical, lithological, granulometric, and mineralogical properties of the sedimentary sequences drilled at ODP Leg 178 Sites 1095 and 1096. The most pronounced coupling is observed between major changes in the biogenic silica/lithogenic content of the recovered drift deposits and the seismic facies of the corresponding seismostratigraphic units. Possible reasons for this connection may be seen in the influence of the biogenic silica content on the dry-bulk density and porosity of the sedimentary sequences. The early idea, that a bottom simulating reflector (BSR) occurring in seismic profiles crossing Drift 7 and drilled through at Site 1095 is caused by diagenetic transformation of opal A to opal CT, is corroborated by indirect mineralogical evidence.



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Conference (Poster)
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Not peer-reviewed
Publication Status
Published
Event Details
EGS-EGU-AGU Joint Assembly, 06.-11. April, Nizza, Frankreich..
Eprint ID
8600
Cite as
Hillenbrand, C. D. , Uenzelmann-Neben, G. , Rebesco, M. , Rendle, R. and Volpi, V. (2003): Sediment properties of drift deposits and their influence on seismic facies - an example from the Antarctic Peninsula continental margin , EGS-EGU-AGU Joint Assembly, 06.-11. April, Nizza, Frankreich. .


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