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<p>Hemipelagic to pelagic (H/P) marls, representing pelitic deposits, accumulated within the foredeep sub-basin of the Dinaric Foreland Basin (northern Neotethyan margin, present-day Croatia) during the Middle to Late Eocene. Syn-sedimentary tectonic movements, paleogeographic position and exchanges of short-lived hyperthermal episodes affected the sedimentation and related mineral and geochemical record of these deposits. Mineral (clay) assemblages bear signature of prevailing physical weathering with significant illite and chlorite content, but climatic seasonality is suggested by smectite-interlayered phases and sporadical increase of kaolinite content. Illite crystallinity varies significantly, and the lowest crystallinity is recorded by the Lutetian samples. Illite chemistry index is always bellow 0.5, being characteristic for Fe-Mg-rich illite. The geochemical records are the most prominent (CIA up to 76, CIW up to 91) for the Istrian Lutetian (42.3–40.5 Ma), but also for Priabonian (35.8–34.3 Ma) samples of Hvar Island. The ICV values (the lowest 1.40 and the highest 10.85) of all studied samples fall above PAAS (ICV = 0.85) and point to their chemical immaturity. The Ga/Rb ratios are lower than 0.2 and K<sub>2</sub>O/Al<sub>2</sub>O<sub>3</sub> ratios are also low (0.16–0.22), implying transition between cold and dry, and warm and humid climate, obviously trending among several warming episodes.</p>

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Eocene Weathering Oscillations Imprinted in Marl Mineral and Geochemical Record, Dinaric Foreland Basin, Croatia

  • 期刊论文

  • 发表日期：

    2025年6月17日

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  • Marija Horvat,
  • Nenad Tomašić,
  • Dunja Aljinović,
  • Damir Bucković,
  • Stjepan Ćorić,
  • Vlasta Ćosović,
  • Igor Felja,
  • Ines Galović,
  • Željko Ištuk,
  • Štefica Kampić,
  • Dražen Kurtanjek,
  • Đurđica Pezelj

摘要

Hemipelagic to pelagic (H/P) marls, representing pelitic deposits, accumulated within the foredeep sub-basin of the Dinaric Foreland Basin (northern Neotethyan margin, present-day Croatia) during the Middle to Late Eocene. Syn-sedimentary tectonic movements, paleogeographic position and exchanges of short-lived hyperthermal episodes affected the sedimentation and related mineral and geochemical record of these deposits. Mineral (clay) assemblages bear signature of prevailing physical weathering with significant illite and chlorite content, but climatic seasonality is suggested by smectite-interlayered phases and sporadical increase of kaolinite content. Illite crystallinity varies significantly, and the lowest crystallinity is recorded by the Lutetian samples. Illite chemistry index is always bellow 0.5, being characteristic for Fe-Mg-rich illite. The geochemical records are the most prominent (CIA up to 76, CIW up to 91) for the Istrian Lutetian (42.3–40.5 Ma), but also for Priabonian (35.8–34.3 Ma) samples of Hvar Island. The ICV values (the lowest 1.40 and the highest 10.85) of all studied samples fall above PAAS (ICV = 0.85) and point to their chemical immaturity. The Ga/Rb ratios are lower than 0.2 and K2O/Al2O3 ratios are also low (0.16–0.22), implying transition between cold and dry, and warm and humid climate, obviously trending among several warming episodes.