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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 65 (1981)

Issue: 5. (May)

First Page: 985

Last Page: 985

Title: Pennsylvanian Aragonite from Southeastern Kansas--Environmental and Diagenetic Implications: ABSTRACT

Author(s): P. A. Sandberg, Brian N. Popp

Article Type: Meeting abstract



Unaltered acicular aragonite cements have been found in Pennsylvanian limestones from southeastern Kansas as spherulitic arrays encased in pore-filling spar in intragranular voids. Identical cements are documented in Pleistocene carbonate rocks. Associated early cements in intergranular pores include aragonite botryoids now altered to irregular neomorphic calcite, and bladed calcites inferred to have been precipitated as magnesian calcite. In addition, phylloid algal blades of Archaeolithophyllum, now altered to irregular neomorphic calcite mosaics, contain varying concentrations of oriented inclusions of original aragonite. The unaltered aragonite cement was apparently protected from diagenetic alteration by the enclosing calcite spar and organic matter on the skeletal substrate. Ind vidual aragonite relics in the algae probably survived because of enclosure in organic envelopes, a phenomenon observed in Pleistocene examples.

We see two explanations for the precipitation of these metastable carbonate cements in Pennsylvanian seas, both of which raise perplexing questions regarding ancient carbonate deposition. (1) Several authors have suggested a domination of calcite in Paleozoic non-skeletal carbonate deposition; our cements could represent some local departure from that general pattern, or (2) these carbonates document part of a long-term temporal trend in non-skeletal carbonate mineralogy from a domination of calcite in Paleozoic seas to aragonite and magnesian calcite domination in Quaternary seas. However, later calcite domination as evidencd by calcite cements and ooids in the Jurassic and Cretaceous, suggests that if the latter explanation is accepted the postulated trend was neither simple nor uni irectional.

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