TY - JOUR

T1 - Statistical evaluation of elemental concentrations in shallow-marine deposits (Cretaceous, Lusitanian Basin)

AU - Coimbra, Rute

AU - Horikx, Maurits

AU - Huck, Stefan

AU - Heimhofer, Ulrich

AU - Immenhauser, Adrian

AU - Rocha, Fernando

AU - Dinis, Jorge

AU - Duarte, Luís Vitor

N1 - Funding information: The authors wish to thank Dieter Buhl, Andrea Niedermayr, Beate Gehnen and Kathrin Schauerte (Ruhr-University Bochum-RUB) for their collaboration during elemental measurements; Denise Terroso for the support during mineralogical analysis; and Maria Cristina Sequeira for assistance during SEM-EDS. Benoit Vincent is thanked for constructive comments on a previous version of this paper and Sebastian Breitenbach for helpful discussions. The first author is supported by the Post-Doctoral Fellowship SFRH/BPD/92376/2013 (Fundação para a Ciência e Tecnologia- FCT , Portugal) and the research units GeoBiotec - UID/GEO/04035/2013 and MARE - UID/MAR/04292/2013 and Maurits Horikx from Deutsche Forschungsgemeinschaft (DFG) project HE4467/6-1 . Editorial guidance by Ihsan Al-Aasm and constructive comments by two anonymous reviewers are acknowledged.

PY - 2017/9

Y1 - 2017/9

N2 - The elemental geochemistry of ancient shallow-marine carbonates represents an often underexplored archive of paleoenvironmental change and diagenetic pathways. Complex multi-parameter datasets from a lithologically heterogeneous sedimentary succession in the southern part of the Lusitanian Basin (Ericeira, Portugal) are presented and interpreted. The section comprises marly, carbonate, and sandstone-rich coastal-marine deposits of early Albian to early Cenomanian age. Principal component analysis of bulk elemental abundance (Ca, Mg, Sr, Fe, and Mn) lead to define four geochemical clusters based on common elemental attributes. Siliciclastics and dolomitized limestones facies yield evidence for significant diagenetic alteration, but still preserve information on paleoshoreline position. Mixed carbonate-siliciclastics and limestone facies bear evidence for relative sea-level position and relevant paleoclimatic information in their elemental record. Accordingly, mid-Albian mixed carbonate-siliciclastic deposits present variable degrees of continental influx. Specifically, a sharp increase of Fe and Mn concentrations in relation to continental input is in agreement with periods of enhanced hydrological cycling and increased weathering on adjacent emerged lands. The progressive transition towards more marine conditions is accompanied by higher Ca and Sr content and represented by limestone facies corresponding to a higher sea-level position during late Albian to early Cenomanian times. Moreover, this facies records a trend towards warmer and more arid conditions. Early diagenetic stabilization and /or dissolution of aragonite into low-Mg calcite can account for major elemental variations, including higher Sr content strongly coupled with Ca content, along with lower Mg, Fe and Mn concentrations. Data shown here provide solid evidence that the statistical analysis of the elemental record of ancient marine deposits, when combined with conventional sedimentology and thin section petrography, allow for elaborate conclusions on their depositional environment and diagenetic pathways. Cored wells and facies-specific reservoir properties can be addressed by these methodologies, able to detect and quantify changes in patterns. Both industry and academy can therefore benefit from approaching such a complex interplay.

AB - The elemental geochemistry of ancient shallow-marine carbonates represents an often underexplored archive of paleoenvironmental change and diagenetic pathways. Complex multi-parameter datasets from a lithologically heterogeneous sedimentary succession in the southern part of the Lusitanian Basin (Ericeira, Portugal) are presented and interpreted. The section comprises marly, carbonate, and sandstone-rich coastal-marine deposits of early Albian to early Cenomanian age. Principal component analysis of bulk elemental abundance (Ca, Mg, Sr, Fe, and Mn) lead to define four geochemical clusters based on common elemental attributes. Siliciclastics and dolomitized limestones facies yield evidence for significant diagenetic alteration, but still preserve information on paleoshoreline position. Mixed carbonate-siliciclastics and limestone facies bear evidence for relative sea-level position and relevant paleoclimatic information in their elemental record. Accordingly, mid-Albian mixed carbonate-siliciclastic deposits present variable degrees of continental influx. Specifically, a sharp increase of Fe and Mn concentrations in relation to continental input is in agreement with periods of enhanced hydrological cycling and increased weathering on adjacent emerged lands. The progressive transition towards more marine conditions is accompanied by higher Ca and Sr content and represented by limestone facies corresponding to a higher sea-level position during late Albian to early Cenomanian times. Moreover, this facies records a trend towards warmer and more arid conditions. Early diagenetic stabilization and /or dissolution of aragonite into low-Mg calcite can account for major elemental variations, including higher Sr content strongly coupled with Ca content, along with lower Mg, Fe and Mn concentrations. Data shown here provide solid evidence that the statistical analysis of the elemental record of ancient marine deposits, when combined with conventional sedimentology and thin section petrography, allow for elaborate conclusions on their depositional environment and diagenetic pathways. Cored wells and facies-specific reservoir properties can be addressed by these methodologies, able to detect and quantify changes in patterns. Both industry and academy can therefore benefit from approaching such a complex interplay.

KW - Carbonate geochemistry

KW - Diagenesis

KW - Paleoenvironment

KW - Statistical analysis

UR - http://www.scopus.com/inward/record.url?scp=85028909386&partnerID=8YFLogxK

U2 - 10.1016/j.marpetgeo.2017.07.003

DO - 10.1016/j.marpetgeo.2017.07.003

M3 - Article

AN - SCOPUS:85028909386

VL - 86

SP - 1029

EP - 1046

JO - Marine and petroleum geology

JF - Marine and petroleum geology

SN - 0264-8172

ER -