Chalk burial diagenesis

Burial diagenesis and subsequent alteration of chalk The Overall Diagenetic Pathway... 

Many chalks undergoing burial diagenesis in the present oceanic realm and those exposed on land were originally pelagic foram-nannofossil calcite oozes. However, calcareous oozes deposited in the periplatform environment are compositionally more complex. These oozes represent transitional carbonate deposits found between carbonate banks and the deep sea (Schlager and James,... 

Figure 8.21. Strontium, 818C, and 8180 composition of Miocene chalk, northern Jamaica. Subaerially exposed chalks are low in Sr, and depleted in 180 and l3C relative to chalks that have never been exposed to subaerial conditions. The line is the Sr-8180 trend for Shatsky Rise limestones recovered by the DSDP program (Matter et al., 1975). Notice the similarity between the Sr-8180 trends for the Shatsky Rise limestones, which have undergone burial diagenesis, and that for the Jamaican chalks, which have been subjected to meteoric processes. (After Land, 1986.)...

Czemiakowski L.A., Lohmann K.C. and Wilson J.L. (1984) Closed system marine burial diagenesis Isotopic data from the Austin Chalk and its components. Sedimentology 31, 863-877. 

Tectonic events can play a major role in the later history of chalk diagenesis. Subduction and very deep burial can lead to the conversion of calcite to a calc-silicate with release of CO2. As an example, Figure 8.22 illustrates the P-T conditions necessary for the reaction... 

Figure 8.34. Hypothetical porosity-depth curves for various diagenetic situations. A. "Normal" burial curve of chalk sequences. B. A typical curve stemming from porosity changes brought about by dissolution and cementation processes during meteoric zone diagenesis. C. A scenario for late stage porosity development brought about by a dissolution event related to hydrocarbon maturation and destruction. D. Porosity preservation resulting from conditions of overpressuring. (After Choquette and James, 1987.)...

With time and burial, carbonate oozes undergo a progressive sequence of diagenesis and are transformed first to chalk and then to limestone through a combination of gravitational compaction,... 

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