TY - JOUR

T1 - Diagenetic and detrital influences on clay mineralogy and carbon isotope geochemistry of Campanian–Maastrichtian sediments in the Tremp-Graus Basin (southern Pyrenees, Spain)

AU - Chenot, E.

AU - Deconinck, J. F.

AU - Baudin, F.

AU - Cocquerez, T.

AU - Pucéat, E.

AU - Razmjooei, M. J.

AU - Thibault, N.

N1 - Publisher Copyright: © 2021, Universidad Complutense de Madrid.

PY - 2022

Y1 - 2022

N2 - A 1000 m-thick sequence of Upper Cretaceous sediments outcropping in the Isabena Valley (Tremp-Graus Basin, Spain) has been studied to explore the evolution of environmental conditions that prevailed in this basin. A biostratigraphic study based on calcareous nannofossils was carried out to better constraint the age of the deposits, supplemented by carbon isotope stratigraphy on bulk carbonates. Clay mineral assemblages were identified by X-Ray diffraction combined with organic matter (OM) characterisation by Rock–Eval pyrolysis. The Late Campanian Event and Campanian Maastrichtian Boundary Event are clearly identified from the new δ13Ccarb dataset. The clay assemblage is composed of a complex mixture of chlorite, illite, kaolinite and mixed-layers including illite–smectite and chlorite–smectite. A progressive illitisation of smectite is recorded from the top to the base of the section due to the increasing burial depth. This evolution is consistent with increasing Tmax values of OM evolving from 425 (immature OM) to 449 °C (mature OM) from the top to the base of the section. Thus, detrital minerals are preserved only in the upper part of the section. The clay sedimentation is dominated by smectites likely originating from the Ebro massif, while increasing proportions of kaolinite are recorded from the uppermost Campanian and during the Maastrichtian. This evolution of the clay mineral assemblage is interpreted as a result from a change of source from south to northeast, with contributions from kaolinite-rich weathering profiles (including bauxites) to the northeast of the study area, reflecting a more hydrolysing climate.

AB - A 1000 m-thick sequence of Upper Cretaceous sediments outcropping in the Isabena Valley (Tremp-Graus Basin, Spain) has been studied to explore the evolution of environmental conditions that prevailed in this basin. A biostratigraphic study based on calcareous nannofossils was carried out to better constraint the age of the deposits, supplemented by carbon isotope stratigraphy on bulk carbonates. Clay mineral assemblages were identified by X-Ray diffraction combined with organic matter (OM) characterisation by Rock–Eval pyrolysis. The Late Campanian Event and Campanian Maastrichtian Boundary Event are clearly identified from the new δ13Ccarb dataset. The clay assemblage is composed of a complex mixture of chlorite, illite, kaolinite and mixed-layers including illite–smectite and chlorite–smectite. A progressive illitisation of smectite is recorded from the top to the base of the section due to the increasing burial depth. This evolution is consistent with increasing Tmax values of OM evolving from 425 (immature OM) to 449 °C (mature OM) from the top to the base of the section. Thus, detrital minerals are preserved only in the upper part of the section. The clay sedimentation is dominated by smectites likely originating from the Ebro massif, while increasing proportions of kaolinite are recorded from the uppermost Campanian and during the Maastrichtian. This evolution of the clay mineral assemblage is interpreted as a result from a change of source from south to northeast, with contributions from kaolinite-rich weathering profiles (including bauxites) to the northeast of the study area, reflecting a more hydrolysing climate.

KW - Clay minerals

KW - Diagenesis

KW - Late Cretaceous

KW - Palaeoenvironment

KW - Southern Pyrenees

KW - Tremp-Graus Basin

U2 - 10.1007/s41513-021-00180-1

DO - 10.1007/s41513-021-00180-1

M3 - Journal article

AN - SCOPUS:85120616597

VL - 48

SP - 29

EP - 43

JO - Journal of Iberian Geology

JF - Journal of Iberian Geology

SN - 1698-6180

ER -