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Late Ordovician carbonate productivity and glaciomarine record under quiescent and active extensional tectonics in NE Spain

By
J. Javier Álvaro
J. Javier Álvaro
1
Departamento Ciencias de la Tierra
,
Universidad de Zaragoza
,
50009-Zaragoza
,
Spain
2
Sciences de la Terre, Université des Sciences et Technologies de Lille
,
59655-Villeneuve d'Ascq
,
France
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Brigitte Van Vliet-Lanoë
Brigitte Van Vliet-Lanoë
2
Sciences de la Terre, Université des Sciences et Technologies de Lille
,
59655-Villeneuve d'Ascq
,
France
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Published:
January 01, 2009

Abstract

Carbonate productivity and glaciomarine deposits of the Ordovician–Silurian transition display different sedimentary architectures in the Iberian and Hesperian Chains of NE Spain, as a result of quiescent and active extensional tectonics on platforms fringing North Gondwana. The late Katian carbonate productivity of the Iberian platform reflects the onset of bryozoan–pelmatozoan meadows and mud-mound complexes throughout an intra-shelf ramp, whereas carbonate nucleation of prominent carbonate factories took place on the top of isolated palaeo-highs in the Hesperian platform. In both cases, the end of carbonate productivity is associated with glacioeustatic regression, subaerial exposure and karstification, pre-dating widespread precipitation of iron ore deposits in the vicinity of palaeo-highs. The Hirnantian glacioeustatic transgression is represented lithostratigraphically by the Orea Formation. In the Iberian platform, the formation consists of two distinct depositional sequences bounded by the progradation of conglomeratic channels, and is dominated by the record of massive and crudely stratified diamictites, with tabular geometries and deposited subaqueously as ‘rain-out’ facies. In contrast, the Hesperian platform is rich in disrupted diamictites, which form strongly deformed units interpreted as submarine slumps associated with active synsedimentary faults. In both cases, the anomalous occurrence of massive diamictites, rich in boulder- to sand-sized carbonate dropstones, and displaying rapid variations in density and size, suggests that distinct iceberg ‘drift lanes’ existed, indicating current activity in the open sea.

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Geological Society, London, Special Publications

Early Palaeozoic Peri-Gondwana Terranes: New Insights from Tectonics and Biogeography

M. G. Bassett
M. G. Bassett
National Museum of Wales, Cardiff, UK
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Geological Society of London
Volume
325
ISBN electronic:
9781862395732
Publication date:
January 01, 2009

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