Microspar development during early marine burial diagenesis: a comparison of Pliocene carbonates from the Bahamas with Silurian limestones from Gotland (Sweden) |
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| Authors: | AXEL MUNNECKE HILDEGARD WESTPHAL† JOHN J G REIJMER† CHRISTIAN SAMTLEBEN |
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| Institution: | Geologisch-Paläontologisches Institut der Universität Kiel, Olshausenstr. 40–60, D-24118 Kiel, Germany (E-mail: );GEOMAR Forschungszentrum für marine Geowissenschaften, Wischhofstr. 1–3, D-24148 Kiel, Germany (E-mail: ) |
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| Abstract: | Comparison of ultrastructures in Pliocene periplatform carbonates from the Bahamas with Silurian limestones from Gotland (Sweden) reveals that despite the differences in primary sediment composition and age, they reflect a similar mechanism of lithification. In both sequences calcite microspar was formed as a primary cement at an early stage of marine burial diagenesis. Neither significant compression nor meteoric influence are necessary for the formation of calcite microspar. A model is proposed for the process of microsparitic cementation of fine-grained aragonite needle muds comprising four stages: (1) unconsolidated, aragonite-dominated carbonate mud; (2) precipitation of microspar that engulfs aragonite needles; (3) dissolution of aragonite, resulting in pitted surfaces of the microspar crystals; and (4) slight recrystallization. Our results contradict the widespread opinion that microspar necessarily is a product of secondary recrystallization of a previously lithified micrite. |
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