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Comparing the depositional architecture of basin floor fans and slope fans in the Pab Sandstone, Maastrichtian, Pakistan

By
R. Eschard
R. Eschard
Institut Français du Pétrole, 1, 4 Avenue de Bois Préau, 92852 Rueil-Malmaison Cedex, France
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E. Albouy
E. Albouy
Institut Français du Pétrole, 1, 4 Avenue de Bois Préau, 92852 Rueil-Malmaison Cedex, France
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F. Gaumet
F. Gaumet
Institut Français du Pétrole, 1, 4 Avenue de Bois Préau, 92852 Rueil-Malmaison Cedex, France
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A. Ayub
A. Ayub
Premier Pakistan, 4th floor, Jang building, Fazal-e-Haq road, Blue area, Islamabad, Pakistan
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Published:
January 01, 2004

Abstract

Basin-floor fans and slope fans present major differences in their internal architecture related to changes in: (1) margin morphology, (2) relative sea-level change, and (3) sediment supply. These variations are illustrated in the outcrops of the Pab Sandstone in Pakistan. The Pab Sandstone third-order sequence was deposited on the Indo-Pakistani margin during the Upper Maastrichtian. Uplift of the margin induced erosion on the shelf, incision of submarine canyons on the slope and the development of a sand-rich, high-efficiency basin-floor fan extending over hundreds of kilometres on the basin floor. During transgression, sediment accumulated in backstepping shoreface deposits on the shelf, and a minor mud-rich slope fan was deposited in the basin. Finally, a sand-rich braided delta prograded across the shelf, feeding a sand-rich slope fan where it reached the shelf margin. This slope fan was of more limited lateral extent. The Lower Pab basin-floor fan shows the effects of flow funnelling and confinement due to a canyon incised into the slope. It consists mainly of channel complexes deposited by superconcentrated density flows to low-density turbidity currents. In contrast, the Upper Pab slope fan shows little confinement and low transport efficiency. It consists of tabular lobes, aggrading mid-fan channels and conglomeratic channels in the upper fan. The low transport efficiency of the gravity flows probably explains the low degree of organization of the slope fan.

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Contents

Geological Society, London, Special Publications

Confined Turbidite Systems

S. A. Lomas
S. A. Lomas
Baker Atlas Geoscience, UK
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P. Joseph
P. Joseph
Institut Français du Petrole, France
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Geological Society of London
Volume
222
ISBN electronic:
9781862394704
Publication date:
January 01, 2004

GeoRef

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