Facies architecture of the CRP-3 drillhole, Victoria Land Basin, Antarctica

Fielding, C. R., Naish, T.R. and Woolfe, K.J. (2001) Facies architecture of the CRP-3 drillhole, Victoria Land Basin, Antarctica. Terra Antartica, 8 3: 217-224.


Author Fielding, C. R.
Naish, T.R.
Woolfe, K.J.
Title Facies architecture of the CRP-3 drillhole, Victoria Land Basin, Antarctica
Journal name Terra Antartica   Check publisher's open access policy
ISSN 1122-8628
Publication date 2001
Sub-type Article (original research)
Volume 8
Issue 3
Start page 217
End page 224
Total pages 8
Editor Peter J Barrett
Carlo Alberto Ricci
Place of publication Siena
Publisher Terra Antartica Publication
Collection year 2001
Language eng
Subject C1
260104 Sedimentology
780104 Earth sciences
0499 Other Earth Sciences
Abstract The Cenozoic Victoria Land Basin (VLB) stratigraphic section penetrated by CRP-3 is mostly of Early Oligocene age. It contains an array of lithofacies comprising fine-grained mudrocks, interlaminated and interbedded mudrocks/sandstones, mud-rich and mud-poor sandstones, conglomerates and diametites that are together interpreted as the products of shallow marine to possibly non-marine environments of deposition, affected by the periodic advance and retreat of tidewater glaciers. This lithofacies assemblage can be readily rationalised using the facies scheme designed originally for CRP-2/2A, and published previously. The uppermost 330 metres below sea floor (mbsf) shows a cyclical arrangement of lithofacies also similar to that recognised throughout CRP-2/2A, and interpreted to reflect cyclical variations in relative sea-level driven by ice volume fluctuations ("Motif A"). Between 330 and 480 mbsf, a series of less clearly cyclical units, generally fining-upward but nonetheless incorporating a significant subset of the facies assemblage, has been identified and noted in the Initial Report as "Motif B. Below 480 mbsf, the section is arranged into a repetitive succession of fining-upward units, each of which comprises dolerite clast conglomerate at the base passing upward into relatively thick intervals of sandstones. The cycles present down 480 mbsf are defined as sequences, each interpreted to record cyclical variation of relative sea-level. The thickness distribution of sequences in CRP-3 provides some insights into the geological variables controlling sediment accumulation in the Early Oligocene section. The uppermost part of the section in CRP-3 comprises two or three thick, complete sequences that show a broadly symmetrical arrangement of lithofacies (similar to Sequences 9-11 in CRP-2/2A). This suggests a period of relatively rapid tectonic subsidence, which allowed preservation of the complete facies cycle. Below Sequence 3, however, is a considerable interval of thin, incomplete and erosionally truncated sequences (4-23), which incorporates both the remainder of Motif A sequences and all Motif B sequences recognised. The thinner and more truncated sequences suggest sediment accumulation under conditions of reduced accommodation, and given the lack of evidence for glacial conditions (see Powell et al., this volume) tends to argue for a period of reduced tectonic subsidence. The section below 480 mbsf consists of a series of fining-upward, conglomerate to sandstone intervals which cannot be readily interpreted in terms of relative sea-level change. A relatively mudrock-rich interval above the basal conglomerate/breccia (782-762 mbsf) may record initial flooding of the basin during early rift subsidence. The lithostratigraphy summarised above has been linked to seismic reflection data using depth conversion techniques (Henrys et al., this volume). The three uppermost reflectors ("o", "p" and "q") correlate to the package of thick sequences 1-3, and several deeper reflectors can also be correlated to sequence boundaries. The package of thick Sequences 1-3 shows a sheet-like cross-sectional geometry on seismic reflection lines, unlike the similar package recognised in CRP-2/2A.
Keyword Cenozoic
Sea levels
seismic reflection
Q-Index Code C1

Document type: Journal Article
Sub-type: Article (original research)
Collection: Earth Systems Science Computational Centre Publications
 
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Created: Tue, 14 Aug 2007, 15:26:23 EST