GRANMUD: Granulometric and geochemical contrast comparison of carbonate mud lithified under natural and laborytory conditions

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Carbonate ooze, or micrite, its lithified counterpart, forms a main constituent of limestones throughout Earth History. Micrite data commonly represent a geochemical average of the depositional environmeht, but their origin (platform, slope, water column, authigenic) and mineralogy (aragonite, (Mg-)calcite) is often poorly constrained as is the geochemical and Volumetrie significance of carbonate precipitates formed during cementation. This is referred as the micrite problem . Bulk-matrix micrites form the (poorly understood) backbone of many geochemical studies dealing with past carbon cycle or chemostratigraphy. Here l propose to investigate marine carbonate oozes naturally lithified within the sediment column to variable degrees and to compare granulometric data from such micrites with such from carbonate oozes lithified under controlled laboratory conditions. The focus is both on aragonite mud (marine) as well as calcite mud (lacustrine). In the laboratory, carbonate muds are lithified using a tracer element in order to clearly separate precipitated (cement) and detrital (mud) components. The goal is to physically separate specific components of micrite and to investigate their origin, mineralogy, grain morphology and geochemistry. It is proposed to use the well established Paris method and to test the new Kiel (SPLITT) method. It is acknowledged that neither method can compensate for any post-depositional diagenetic alteration of aragonitic or high-Mg calcitic oozes but it is believed that this research is an important step in the right direction.