TY - JOUR

T1 - Coastal sediments from the Algarve

T2 - Low-latitude climate archive for the Aptian-Albian

AU - Heimhofer, Ulrich

AU - Adatte, Thierry

AU - Hochuli, Peter A.

AU - Burla, Stefan

AU - Weissert, Helmut

N1 - Funding Information: Acknowledgments We thank Philipp Steinmann (University of Neuchâtel) for Rock-Eval pyrolysis determinations, Jens Herrle (University of Liverpool) and Stephen Hesselbo (University of Oxford) for discussion and corrections on an earlier draft and J. Dinis (University of Coimbra) and P. Skelton (Open University, Milton Keynes) for assistance in the field. The constructive comments of two anonymous reviewers are highly appreciated. Financial support from ETH-Project TH-34/99-4 and DFG project HE 4467/1-1 to UH is gratefully acknowledged.

PY - 2008/7

Y1 - 2008/7

N2 - The Late Aptian to Early Albian transition has previously been identified as a possible example of substantial climate cooling within the mid-Cretaceous greenhouse period. To study the response of continental weathering and terrestrial vegetation to this cooling episode at low- to mid-latitudes, marine nearshore deposits from the Algarve Basin (SW Portugal) have been investigated with a combined approach including palynology, clay mineralogy and bulk-rock geochemistry. In the Lower Aptian part of the succession, quartz-rich sandstone facies is accompanied by high abundances of early diagenetic kaolinite, which is interpreted to reflect episodes of enhanced humidity and high meteoric flow-through. In contrast, the Late Aptian to Early Albian deposits are characterized by high abundances of detrital clay minerals (mica and chlorite) indicating the dominance of physical weathering processes in the source area, most probably related to low precipitation rates in conjunction with tectonically enhanced erosion. Palynological data show a strong dominance of Classopollis pollen associated with low pteridophyte spore abundances, suggesting warm semi-arid to arid palaeoenvironments. Changes in sedimentation patterns from varicoloured lagoonal marls to thick-bedded shallow-water carbonates are neither expressed in the spore-pollen assemblages nor in the distributions of clay minerals which both remain essentially stable throughout the Late Aptian to Early Albian. These relatively stable patterns are in contrast with various lines of evidence, predominantly from high-latitude areas, that suggest a significant cooling during this time interval. Our study demonstrates that terrestrial environments of low- to mid-latitude regions were not significantly affected by the Late Aptian - Early Albian "cold snap".

AB - The Late Aptian to Early Albian transition has previously been identified as a possible example of substantial climate cooling within the mid-Cretaceous greenhouse period. To study the response of continental weathering and terrestrial vegetation to this cooling episode at low- to mid-latitudes, marine nearshore deposits from the Algarve Basin (SW Portugal) have been investigated with a combined approach including palynology, clay mineralogy and bulk-rock geochemistry. In the Lower Aptian part of the succession, quartz-rich sandstone facies is accompanied by high abundances of early diagenetic kaolinite, which is interpreted to reflect episodes of enhanced humidity and high meteoric flow-through. In contrast, the Late Aptian to Early Albian deposits are characterized by high abundances of detrital clay minerals (mica and chlorite) indicating the dominance of physical weathering processes in the source area, most probably related to low precipitation rates in conjunction with tectonically enhanced erosion. Palynological data show a strong dominance of Classopollis pollen associated with low pteridophyte spore abundances, suggesting warm semi-arid to arid palaeoenvironments. Changes in sedimentation patterns from varicoloured lagoonal marls to thick-bedded shallow-water carbonates are neither expressed in the spore-pollen assemblages nor in the distributions of clay minerals which both remain essentially stable throughout the Late Aptian to Early Albian. These relatively stable patterns are in contrast with various lines of evidence, predominantly from high-latitude areas, that suggest a significant cooling during this time interval. Our study demonstrates that terrestrial environments of low- to mid-latitude regions were not significantly affected by the Late Aptian - Early Albian "cold snap".

KW - Algarve Basin

KW - Clay mineralogy

KW - Early Cretaceous

KW - Palaeoclimate

KW - Palynology

UR - http://www.scopus.com/inward/record.url?scp=44849138414&partnerID=8YFLogxK

U2 - 10.1007/s00531-007-0186-y

DO - 10.1007/s00531-007-0186-y

M3 - Article

AN - SCOPUS:44849138414

VL - 97

SP - 785

EP - 797

JO - International Journal of Earth Sciences

JF - International Journal of Earth Sciences

SN - 1437-3254

IS - 4

ER -