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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 65 (1981)

Issue: 5. (May)

First Page: 927

Last Page: 927

Title: No Title Provided: ABSTRACT

Author(s): Tom Freeman, David Rothbard, Antonio Obrador


Miocene calcarenites of Menorca exhibit abundant terrigenous dolomite, both as medium-grained polycrystalline rock fragments and as fine-grained individual abraded crystals. Petrographically, this detritus looks both like neighboring Jurassic dolostones and like Triassic Muschelkalk dolostones of the same general area. To determine which stratigraphic unit(s) provided this terrigenous dolomite we characterized the iron contents of Jurassic and Triassic dolostones, using the electron microprobe, and then, with the probe, we matched the composition of the Miocene detritus with its source. As was expected from their present greater surface exposure, Jurassic dolostones proved to be the principal source. The trace of Triassic dolomite detritus in Miocene samples analyzed is p oportionate to the small area of Triassic exposure relative to that of the Jurassic.

Dolomitization of the Miocene resulted in (1) pervasive fine to medium-crystalline dolomite and (2) overgrowths on terrigenous dolomite grains. In some samples, dolomite overgrowths occur in the absence of pervasive dolomite, indicating that seeding by terrigenous dolomite grains enhanced dolomitization. Later calcitization of Miocene dolomite favored centers of the pervasive variety of dolomite crystals and the inner margins of the dolomite overgrowths. These patterns of dedolomite indicate that the two occurrences of dolomite, the pervasive variety and the dolomite overgrowths, are behaviorly correlative, and suggest that they are temporally correlative as well.

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