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The AAPG/Datapages Combined Publications Database

CSPG Special Publications

Abstract


Shelf Sands and Sandstones — Memoir 11, 1986
Pages 331-332
Symposium Abstracts: Tectonic Control

A Transgressive Sand Wave Complex in Relation to a Peculiar Strait Paleogeography: Folgueroles Sandstone, Middle to Upper Eocene, Southern Pyrenees: Abstract

A. Bamolas1, C. Puigdefabregas2

Abstract

The Folgueroles Sandstone is a Middle to Upper Eocene Formation with a peculiar and very definite sequential and paleogeographic situation at the eastern end of the southern Pyrenean basin. The basin geometry, inherited from a Mesozoic pull-apart pattern, includes a northern active margin (Pyrenean compression) and a southern passive margin (Catalan coastal ranges).

The Eocene fill of the southern Pyrenean basin consists of a succession of five depositional cycles, which are characterized by a stepwise shift of the basin axis to the south (transgressed passive margin) as a response to thrusting in the northern active margin.

A Mediterranean polarity for the third cycle is well documented from the geometry of the sedimentary fill and from the faunal assemblages. The fourth cycle is expansive and seems to have an Atlantic polarity with mixed faunal assemblages. During the transition from the third to fourth cycles, a 10-km wide strait allowed Atlantic-Mediterranean communication. It was then that the Folgueroles sandstone was deposited from reworking of the coastal fans surrounding the southern passive margin (weathered granitic sands). The sandstone body consists of poorly sorted, medium- to coarse-grained glauconitic sands with west-oriented, large-scale trough sets up to 10 m thick, which resulted from sand wave migration. An intricate superposition of stacked sets and erosive surfaces gives a massive appearance without a definite sequential character. It shows a lens geometry with a maximum thickness of 60 m, an observable length of 30 km and a width of 10 km. The estimated volume is about 5 km3.

The determining conditions for the accumulation of such a massive sandstone body were: 1. sand availability, 2. transgressive conditions, 3. a strait paleogeography with strong and persistent currents, and 4. low rate of subsidence.


 

Acknowledgments and Associated Footnotes

1 Instituto Geologico y Minero de Espana, Rio Rosas, 23, Madrid

2 Servei Geologic de Catalunya, Urgell, 187, Barcelona-36, Spain

Copyright © 2008 by the Canadian Society of Petroleum Geologists