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Climate and vegetation history of western Portugal inferred from Albian near-shore deposits (Galé Formation, Lusitanian Basin)

Published online by Cambridge University Press:  01 May 2012

ULRICH HEIMHOFER ,
PETER-A. HOCHULI ,
STEFAN BURLA ,
FELIX OBERLI ,
THIERRY ADATTE ,
JORGE L. DINIS  and
HELMUT WEISSERT
ULRICH HEIMHOFER*
Affiliation:
Institute of Geology, Leibniz University Hannover, 30167 Hannover, Germany
PETER-A. HOCHULI
Affiliation:
Palaeontological Institute, University of Zürich, CH-8006 Zürich, Switzerland
STEFAN BURLA
Affiliation:
Geological Institute, ETH Zürich, CH-8092 Zürich, Switzerland
FELIX OBERLI
Affiliation:
Institute of Geochemistry and Petrology, ETH Zürich, CH-8092 Zürich, Switzerland
THIERRY ADATTE
Affiliation:
Institute of Geology and Palaeontology, Université de Lausanne, CH-1015 Lausanne, Switzerland
JORGE L. DINIS
Affiliation:
Departamento de Ciências da Terra, Universidade de Coimbra, 3000 Coimbra, Portugal
HELMUT WEISSERT
Affiliation:
Geological Institute, ETH Zürich, CH-8092 Zürich, Switzerland
*
†Author for correspondence: [email protected]
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Abstract

The late Early Cretaceous greenhouse climate has been studied intensively based on proxy data derived essentially from open marine archives. In contrast, information on continental climatic conditions and on the accompanying response of vegetation is relatively scarce, most notably owing to the stratigraphic uncertainties associated with many Lower Cretaceous terrestrial deposits. Here, we present a palynological record from Albian near-shore deposits of the Lusitanian Basin of W Portugal, which have been independently dated using Sr-isotope signals derived from low-Mg oyster shell calcite. 87Sr/86Sr values fluctuate between 0.707373 ± 0.00002 and 0.707456 ± 0.00003; absolute values and the overall stratigraphic trend match well with the global open marine seawater signature during Albian times. Based on the new Sr-isotope data, existing biostratigraphic assignments of the succession are corroborated and partly revised. Spore-pollen data provide information on the vegetation community structure and are flanked by sedimentological and clay mineralogical data used to infer the overall climatic conditions prevailing on the adjacent continent. Variations in the distribution of climate-sensitive pollen and spores indicate distinct changes in moisture availability across the studied succession with a pronounced increase in hygrophilous spores in late Early Albian times. Comparison with time-equivalent palynofloras from the Algarve Basin of southern Portugal shows pronounced differences in the xerophyte/hygrophyte ratio, interpreted to reflect the effect of a broad arid climate belt covering southern and southeastern Iberia during Early Albian times.

Keywords

Albian StageSr-isotopespalynologyclay mineralogypalaeoclimatePortugal
Type
Original Articles
Information
Geological Magazine , Volume 149 , Issue 6 , November 2012 , pp. 1046 - 1064
Copyright
Copyright © Cambridge University Press 2012

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