Variations in primary aragonite, calcite, and clay in fine-grained calcareous rhythmites of Cambrian to Jurassic age— an environmental archive?

摘要: Limestone-marl alternations represent a common type of fine-grained calcareous rhythmites during the entire Phanerozoic. Their diagenetic overprint, however, obliterates their value for palaeoenvironmental interpretations. The original mineralogical composition carbonate fraction (aragonite, high-Mg calcite, low-Mg calcite) would potentially yield important information on conditions: example shallow-water factories are usually characterised by extensive aragonite production, whereas pelagic production is dominated calcitic organisms. Therefore, reconstruction pre-diagenetic limestone-marl precursors be desirable.