Biostratigraphy of Lower Permian foraminiferal assemblages from platform-slope carbonate blocks within the Mersin Mélange, southern Turkey: Paleogeographical implications

Abstract

The Mersin Mélange (MM) as a part of the Mersin Ophiolitic Complex in southern Turkey is a sedimentary complex including blocks and tectonic slices within a Late Cretaceous matrix. Two blocks (Keven and Cingeypinari) within the MM originated from the northern branch of Neotethys (Izmir-Ankara-Erzincan Ocean) and have been studied in detail using foraminiferal assemblages to correlate them with coeval successions in the Taurides and to approach the Early Permian evolution of the northern branch of the Neotethys. The Keven block includes mainly slope deposits (poorly-sorted carbonate breccia and fossiliferous calcarenite) and dated as late Asselian-Sakmarian, whereas the Cingeypinari block consists of platform deposits (fossiliferous platform carbonate and quartz sandstone alternation) assigned to the Sakmarian-early Artinskian. These Early Permian Cingeypinari and Keven blocks from the Beysehir-Hoyran Nappes are biostratigraphically well correlated to the northerly originated Hadim nappe and its equivalents in the Tauride Belt. Considering recent studies on the Mersin Mélange, a possible mantle plume existed during the Late Carboniferous-Early Permian time interval along the northern Gondwanan margin. This event led to the opening of the northern Neotethys and deposition of the pelagic “Karincali” sequence with volcanic material in the basinal conditions. The data presented suggest that the Keven block relates to the slope and the Cingeypinari block to platform conditions deposited as a lateral equivalent of the Karincali sequences during the Early Permian.

Introduction

The Taurides, one of the major units of the Alpine-Himalayan orogenic belt, are characterized by an autochthonous belt ranging in age from Cambrian to Eocene, and allochthonous units comprising oceanic and platform margin-slope sequences that derived from both the north and south of the platform (Özgül, 1976, Özgül, 1984, Özgül, 1997, Şengör and Yilmaz, 1981). Some authors, including Blumenthal, 1947, Blumenthal, 1951, Brunn et al., 1971, Brunn et al., 1973, Monod (1977), Gutnic et al. (1979), etc., identified the allochthonous units as nappes, whereas Özgül, 1976, Özgül, 1984, Özgül, 1997 regarded them as tectono-stratigraphic units. This tectonic complex comprises one of the larger ophiolitic complex (Mersin Ophiolitic Complex, MOC) to the northwest of Mersin town in southern Turkey (Fig. 1, inset map). The MOC is composed of two different units: the Mersin Mélange (MM) and Mersin Ophiolite with its sub-ophiolitic metamorphic base. The geological and geochemical features of the MOC have been studied by various authors (e.g., Pampal, 1984, Pampal, 1987, Parlak et al., 1995, Parlak et al., 1996a, Parlak et al., 1996b, Parlak and Delaloye, 1996, Parlak and Delaloye, 1999, Parlak and Robertson, 2004, Özer et al., 2004, Moix et al., 2007, Moix et al., 2008, Moix et al., 2011). However, the detailed stratigraphy, ages and the source area of the blocks in the MM are still debated. According to the recent studies of Tekin et al., 2016a, Tekin et al., 2016b and Sayit et al. (2017), the MM is a sedimentary mélange including blocks and tectonic slices of variable sizes and diverse origins, which are mainly thought to be the remnants of the Beysehir-Hoyran Nappes of Brunn et al., 1970, Brunn et al., 1971, or the Bozkir Unit of Özgül, 1976, Özgül, 1984, Özgül, 1997 that originated from the Izmir-Ankara-Erzincan Ocean of the northern Neotethys. These blocks are embedded in a Late Cretaceous olistostromal sandy-clayey clastic matrix whose composition remains largely homogeneous throughout the mélange (Tekin et al., 2016a).

The detail study of Tekin et al. (2016b) on the MM revealed the presence of blocks and tectonic slices of thick basaltic pillow- and massive lava sequences stratigraphically overlain by pelagic-clastic sediments and radiolarian chert of middle to latest Anisian age. The geochemical study of Sayit et al. (2017) suggested that the underlying pillow- and massive lava sequences were generated in an intra-oceanic back-arc basin during the late Anisian. Additionally, Okuyucu et al. (2018), Forel et al. (2019) and Tekin et al. (2019) documented that the biochoronology of the blocks and tectonic slices within the MM based on different fossil groups (fusulinids, ostracods and radiolarians) varies between the Lower Carboniferous (upper Tournasian) and the lower Upper Triassic (middle Carnian). These studies not only suggest the presence of a northern Neotethyan oceanic crust older than the late Anisian, but also infer the existence of a continental rift system associated with a possible mantle plume during the late Early to Late Permian.

The aim of this study is presenting additional data from the Early Permian blocks within the MM to reconstruct the Late Carboniferous-Early Permian geological evolution of the northern margin of the Tauride–Anatolide Platform which is assumed to be the source area of the studied Lower Permian blocks. For this, the foraminiferal and algal assemblages of two blocks (originated from two different locations with platform and slope facies) have been documented, and these assemblages have been correlated with the different units in the Taurides. In addition to these, by using combined data it is aimed to propose the positions of different sequences in Beysehir-Hoyran and Hadim Nappes during the Late Carboniferous-Early Permian interval.