Foraminiferal and algal biostratigraphy and petrology of the triassic to early cretaceous carbonate assemblages in the Karaburun peninsula (Western Turkey)

The Mesozoic carbonate assemblage of the central region of the Karaburun Peninsula is stratigraphically and paleontologically investigated. The Mesozoic carbonate assemblage rests on the basement rocks which bound each other along problematical contacts. The contact of the Mesozoic assemblage and the Carboniferous (Bashkirian) Limestone unit seems to be an unconformity. The contact between the Mesozoic assemblage and the Blocky-turbiditic clastic unit, on the other hand, is a displacement plane. The Mesozoic carbonate assemblage consists of, from base to top, pre-Middle Anisian and/or Middle Anisian Gerence Formation, Middle Anisian to Norian Camiboğazı Formation, Norian Güvercinlik Formation, Rhatian to Middle Liassic Nohutalan Formation, Kimmeridgian Birgi Formation and Albian and/or post-Albian Aktepe Formation. The Camiboğazı Formation is divided into Middle Anisian to Ladinian Laleköy, Ladinian to Carman Saplazdağı and Camian to Norian Hanayh Members. The Nohutalan Formation is divided informally into Rhaetian to Early Liassic Lower limestone an Early to Middle Liassic Upper limestone subunits. The Aktepe Formation is divided informally into Albian Limestone and Albian and/or post-Albian Limestone-conglomerate subunits. The Mesozoic sequence is interrupted by two bauxite-bearing unconformity surfaces which correspond to the Middle Liassic to Kimmeridgian and Kimmeridgian to Albian time intervals, respectively. The pre-Middle and/or Middle Anisian lowermost part of the Mesozoic carbonate rocks reflect deep sea to fore slope conditions. The uppermost part of Middle Anisian IVrocks indicate carbonate platform and carbonate build up environments. The Middle Anisian to Norian limestones precipitated mainly in the fore-slope, subtidal, open shelf to lagoonal platform and subtidal to intertidal environments, respectively. The Middle Norian formations display sporadic beach conditions and shallow restricted shelf conditions. The Rhaetian to Liassic part of the sequence precipitated in restricted circulation shallow platform conditions with subtidal to intertidal intercalations. The sequence is interrupted by a bauxite-bearing unconformity which is thought to be formed in a lowland coastal environment at the end of Middle Liassic. The Upper Jurassic part of the sequence precipitated in an open shelf platform environment and is interrupted by a second bauxite-bearing unconformity surface which corresponds to a lowland coastal environment. Uppermost part of the sequence precipitated in open to restricted shelf environment evolving to fore-slope and shallow water marine conditions, respectively. In the study 105 Triassic, 25 Jurassic and 28 Cretaceous foraminiferal taxa, and 21 Triassic, 3 Jurassic and 9 Cretaceous algal taxa are determined. Foraminiferal and algal determinations revealed detailed ages for the sequence. In the Triassic formations from base to top, Meandrospira dinarica concurrent range zone for Middle Anisian (Pelsonian), Turriglomina mesotriassia range zone for the Pelsonian-Cordevalian time interval, Triadodiscus eomesozoicus partial range zone for Ladinian-Carnian, Aulotortus communis interval zone for the Early Norian, Triasina oberhauseri range zone for the Middle Norian, Triasina hantkeni range zone for the Middle-Late Rhaetian time interval are described. In Lower Jurassic formations, Orbitopsella praecursor range-zone for Late Pliensbaschian is suggested. Lower Liassic to Albian rocks contain algal flora indicating a southern Tethyan origin. The Mesozoic sequence are compressed, folded and faulted in the study area. The earliest age of this deformation is thougth to be post- Albian.