TY - BOOK
T1 - Where did it come from, where did it go?
T2 - Carbonate production and resedimentation in the Cretaceous Chalk Sea
AU - Rosing, Salik Anders
PY - 2017
Y1 - 2017
N2 - Late Cretaceous continental margins were inundated during a sea-level highstand of up to 100 m above modernday sea level. In Northwestern Europe, this inundation lead to the creation of the Chalk Sea, in which pelagiccarbonate was deposited, eventually forming the chalk. The chalk has high economic and scientific value.Understanding the processes that formed it is a field of ongoing study.This thesis contributes to the study of the chalk through three interconnected studies.The first study deals with Nd and Pb isotopic data extracted from core material, and reflecting the bottomwater isotopic composition of the chalk sea. εNd values are in therange -12.2 – -13.6, reflecting a significantcontribution from a continental source. We interpret this source to be dense water formation on and cascadingfrom structural highs in the Chalk Sea. Pb isotopic data is hard to put into context, since only a few data pointsare available in the literature for pre-Cenozoic seawater Pb isotopic compositions. However, our results suggestthat attaining such data might be possible through standard extraction methods for Nd.The second study focuses on the numerical modelling of dense water formed on and cascading from structuralhighs, with climatic conditions informed from global simulations of Cretaceous climate. The study shows thatseismic scale depositional features in the Danish Basin and Central Graben of the Chalk Sea can be explainedby sediment enhanced dense water cascading. Currents flowing from adjacent seas are not needed to account forthese features. The model used in this study is idealized, and the process described may be broadly applicableto Cretaceous shelf seas.The third study uses numerical modelling, with a revised version of the setup used in the second study, toinvestigate the effect of sea floor irregularities on primary productivity in the photic zone. The study shows, thatobserved changes in depositional thickness around expressed salt domes can be explained by enhanced primaryproductivity. Sensitivity tests show that this process has a wider application, and suggest that sea floor banksand mounds should be taken into account when analyzing pelagic carbonate systems of the geological past.
AB - Late Cretaceous continental margins were inundated during a sea-level highstand of up to 100 m above modernday sea level. In Northwestern Europe, this inundation lead to the creation of the Chalk Sea, in which pelagiccarbonate was deposited, eventually forming the chalk. The chalk has high economic and scientific value.Understanding the processes that formed it is a field of ongoing study.This thesis contributes to the study of the chalk through three interconnected studies.The first study deals with Nd and Pb isotopic data extracted from core material, and reflecting the bottomwater isotopic composition of the chalk sea. εNd values are in therange -12.2 – -13.6, reflecting a significantcontribution from a continental source. We interpret this source to be dense water formation on and cascadingfrom structural highs in the Chalk Sea. Pb isotopic data is hard to put into context, since only a few data pointsare available in the literature for pre-Cenozoic seawater Pb isotopic compositions. However, our results suggestthat attaining such data might be possible through standard extraction methods for Nd.The second study focuses on the numerical modelling of dense water formed on and cascading from structuralhighs, with climatic conditions informed from global simulations of Cretaceous climate. The study shows thatseismic scale depositional features in the Danish Basin and Central Graben of the Chalk Sea can be explainedby sediment enhanced dense water cascading. Currents flowing from adjacent seas are not needed to account forthese features. The model used in this study is idealized, and the process described may be broadly applicableto Cretaceous shelf seas.The third study uses numerical modelling, with a revised version of the setup used in the second study, toinvestigate the effect of sea floor irregularities on primary productivity in the photic zone. The study shows, thatobserved changes in depositional thickness around expressed salt domes can be explained by enhanced primaryproductivity. Sensitivity tests show that this process has a wider application, and suggest that sea floor banksand mounds should be taken into account when analyzing pelagic carbonate systems of the geological past.
UR - https://rex.kb.dk/primo-explore/fulldisplay?docid=KGL01010669851&context=L&vid=NUI&search_scope=KGL&tab=default_tab&lang=da_DK
M3 - Ph.D. thesis
BT - Where did it come from, where did it go?
PB - Department of Geosciences and Natural Resource Management, Faculty of Science, University of Copenhagen
ER -