Skeletal Grain types

Bivalves

1. Bivalve

Skeletal peloidal grainstone (calcite sparite as cement) containing bivalve shells and gastropods. These molluscs are preserved as micrite envelopes (cortoids) and the original aragonite shells have been replaced by blocky sparite.

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2. Bivalve

Skeletal packstone containing aligned bivalve shells and a gastropod in the centre. Bivalves preserved as cortoids with the micrite envelopes and filled by replacive calcite spar after original aragonite.

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3. Bivalve

Skeletal rudstone/packstone with several mm-large fragments of prismatic layer of Inoceramus bivalve shells in a matrix of planktonic foraminifera (Upper Cretaceous globotruncanids). Inoceramus shells must have been resedimented in basinal environment.

Thin section kindly provided by T. Geel, Vrije Universiteit, Amsterdam

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4. Bivalve

Skeletal packstone to wackestone containing thin-shelled bivalves typical of deep-water deposits and radiolaria (siliceous zooplankton). This is a typical basinal facies of Lower and Middle Jurassic successions.

Thin section kindly provided by T. Geel, Vrije Universiteit, Amsterdam

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5. Bivalve

Skeletal (bivalve) packstone with angular sand-grade quartz grains in the matrix. The thick bivalve shells are oysters.

Thin section kindly provided by T. Geel, Vrije Universiteit, Amsterdam

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6. Lithiotid

Skeletal packstone with a lithiotid bivalve shell characterising the outer platform areas of a Lower Jurassic high-relief platform.

Lower Jurassic, High Atlas, Morocco, cf. Verwer et al. (2009a), Della Porta et al. (2013)

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bivalve micrite envelope

gastropod

gastropod

bivalve micrite envelope

Inoceramus prismatic layer

globotruncanid planktonic foraminifera

thin-shelled bivalve

oysters

detrital quartz sand grain

Lithiotid bivalve

Bivalves

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bivalve micrite envelope

gastropod

gastropod

bivalve micrite envelope

Inoceramus prismatic layer

globotruncanid planktonic foraminifera

thin-shelled bivalve

oysters

detrital quartz sand grain

Lithiotid bivalve