Tectonostratigraphic Study of Carbonate Breccias (Calciturbidites) in the Upper Triassic Baluti Formation (Northern Iraq): New Insights on Tethyan Geodynamics

Abstract

This study aims at describing the sedimentology and geodynamics of the Upper Triassic Baluti Formation from north Iraq. During Late-Triassic period, rift tectonic movement started to spread the Neo-Tethys Ocean in northwest of Gondwana super continent. Intracratonic basins were created where carbonate sediments were deposited in a ramp setting and were interbedded with evaporite near the paleo shore line. The evolution of the rift spreading induced the deposition of polygenetic carbonate breccia and slumps the transition from the ramp to deeper margins. Several types of brecciated sediments are observed in the Baluti Formation. Slump carbonate breccias are arranged in calciturbidite succession and are interbedded with lithic sandstone and thick shale, and sometimes fragmented shales. Along rift-relate fault zones, tectonic breccia was formed. Karstic carbonate breccia type was formed due to the dissolution of evaporites and collapse of the cavities roofs, forming another type of carbonate breccia in the Baluti Formation. Tectogenic-diagenetic breccia was formed due to intense dissolution of the carbonate fragments resulting in a late diagenetic breccia. The circulations of fluids through fault zones led to partial dissolution, dolomitization, dedolomitization, micritic-recrystallization and calcitization processes. The fault systems which resulted from the continuous geodynamic evolution of the rift induced the formation of these various types of carbonate breccias in the Late Triassic period.