--> --> Shallow Water Carbonate Transportation into Pelagic System: Derdere Formation, Arabian Platform, Mardin-Mazidag Area, SE Turkey

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Shallow Water Carbonate Transportation into Pelagic System: Derdere Formation, Arabian Platform, Mardin-Mazidag Area, SE Turkey

Abstract

The study area takes place in the Mardin-Mazidag area, between Diyarbakir and Mardin cities in the SE Turkey. Studied Cenomanian shallow water platform carbonates of the Derdere Formation belonging to middle part of the Mardin Group display a shallowing upward structure from bottom to top. Slope to outer ramp carbonates lies at the bottom and characterized by echinoidal-crinoidal bioclastic wackestone to packstone facies. This facies alternates with bivalve packstones which displays oriented accumulation of monotaxic bivalve species. Matrix of the bivalve packstone is composed of micrite with planktonic foraminifera and partially dolomitized. Bioclastic wackestone and packstone facies with crinoids and echinoids including benthic foraminifera, ammonites and calcispheres take place in the middle part of the section. Nerinid gastrapod, dasyclad algae, benthic foraminifera bearing pelloidal intraclastic wackestone-packstone facies occurs at the top of the section. At this level, nerinid gastrapods displays a relative abundance and alternates with dolostones. The thick dolostones occur below and above the measured section. Bivalve accumulation presents down dip orientation. Inside of the shells includes abundant “Favreina” like caprolite fossils and displays a pelloidal grainstone facies. Shells are embedded in the partially dolomitized micritic matrix. However dolomitization did not affect the infilling material of the shells. According to presence of abundant monotaxic shells infilled by “Favreina” like fossils and with unidirectional orientation within pelagic matrix, it has been interpreted that suspension feeding bivalve shells caused an increase in bioaccumulation on the shelves (Tomasovych et al., 2006) and transported by unidirectional flow on the slope of the Arabian Platform. This study illustrates that monospecific bivalve accumulation (mainly articulated internal moulds) forms a marker bed in the Derdere Formation in the Mardin-Mazidag area. Bivalve shells are oriented towards SE direction with an imbricate fabric. No any different directional or vertical orientations of shells were observed. This indicates that transportation was controlled by current system. No storm or mass flow evidence was observed. Overlying regressive carbonates with abundant nerinid gastrapoda, dasyclad algae, and benthic foraminifera indicate that this part of the Arabian platform was controlled by relative sea-level changes at this locality during the Cenomanian.