Sedimentray Petrography and Origin of Phosphate Peloids of the Mazıdağ-Derik Area (Mardin, Southeast Turkey)

Year 1989, Volume: 109 Issue: 109, 65 - 73, 01.02.1989

Baki Varol

Abstract

 The Mazıdağ phosphate beds of the Upper Cretaceous carbonate sequence were deposited in an area of upwelling
water which supplied phosphorous was deposited on the sea bottom as biogenic detritus of zoo— and phytoplankton, fish bones
and scales. The biogenic accumulation with high content of organic matter and phosphorous was a prime source of the phosphate
which formed the phosphate deposits of the Mazıdağ—Derik area. Commonly, currents transported the phosphatic sediments
laterally, forming parallel and low angle cross laminations. In some cases, the sea floor was uplifted after upwelling periods. Consequently,
some phosphate beds underwent karstification, giving rise to phoscretes and silcretes. Ground water percoalating into the
karstic realm caused phosphate replacement of many carbonate grains of the shallow water limestone facies. These complex events
resulted in the formation of three basic phosphate peloid types in the Mazıdağ-Derik phosphate sequence, which are classified to the
following origin of peloids : (1) in situ precipitation; (2) abrasion of phosphatized intraclast and bioclast and (3) phosphate micritization
of fish bones. The phosphate peloids show the following different microstructures under the electron microscopy : (1)
amorphous; (2) microglobular; (3) semi-crystallized; (4) microcrystallized and (5) cementing. 

Keywords

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