Limestone - Marl alternations in epeiric sea settings - Witnesses of environmental changes or diagnesis?

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Details zur Publikation

Autorinnen und Autoren: Westphal H, Munnecke A, Böhm F, Bornholdt S
Herausgeber: Chris Holmden & Brian R. Pratt
Auflage: 48
Jahr der Veröffentlichung: 2008
Titel der Reihe: Dynamics of Epeiric Seas: Sedimentological, Paleontological and Geochemical Perspectives
Seitenbereich: 389-406
Sprache: Englisch


Abstract


Limestone-marl alternations are widespread and typical sediments of epeiric basins and are present in varying abundance throughout the Phanerozoic. In many cases, their rhythmic appearance has been interpreted as a direct response to orbital forcing. However, it is a challenge to unequivocally prove a sedimentary origin of the rhythmic intercalation of the two lithologies. This difficulty arises from differential diagenesis that alters calcareous beds in different ways than interlayers (marls), causing a loss of comparability between the final lithologies. Differential diagenesis, between other effects, causes passive enrichment of the inert non-carbonate fraction in interlayers, where calcium carbonate is dissolved, as well as passive dilution in limestone beds, which get cemented by imported calcium carbonate. Therefore, reliable information about primary systematic differences in the precursor sediments is preserved only in constituents that are not modified during diagenesis. Such diagenetically inert components include the spectra of organic-walled microfossils (but not their absolute concentration in the bulk sediment) and the ratios of certain trace elements (also not their absolute concentrations). Systematic differences in diagenetically inert components can provide unequivocal proof of primary differences. In the limestone-marl alternations, we have studied however, such aspects do not directly reflect the lithological rhythm, shedding doubt on limestone-marl alternations as direct archives of environmental change. Box-model computer simulations visualize possible effects of early diagenetic change acting on the precursors of limestone-marl alternations, independent of the presence or absence of a primary sedimentary rhythm. The simulations demonstrate that diagenesis has the potential to seriously distort any primary rhythm present in the pristine sediment. In particular, differential compaction acting mainly on the marl interlayers induces distortions of the ratios of the original frequencies. These simulations emphasize the difficulties in conducting frequency analyses on relative carbonate contents in real-world successions.


FAU-Autorinnen und Autoren / FAU-Herausgeberinnen und Herausgeber

Munnecke, Axel Prof. Dr.
Professur für Paläontologie (Schwerpunkt Faziesanalyse)


Einrichtungen weiterer Autorinnen und Autoren

GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel
Hochschule Bremen
Universität Bremen


Forschungsbereiche

Klima und Ressourcen
Forschungsschwerpunkt einer Fakultät: Naturwissenschaftliche Fakultät


Zitierweisen

APA:
Westphal, H., Munnecke, A., Böhm, F., & Bornholdt, S. (2008). Limestone - Marl alternations in epeiric sea settings - Witnesses of environmental changes or diagnesis?

MLA:
Westphal, Hildegard, et al. Limestone - Marl alternations in epeiric sea settings - Witnesses of environmental changes or diagnesis? 2008.

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Zuletzt aktualisiert 2018-14-12 um 09:53