Petrographical and mineralogical study of detrital strata near and within the Ballik travertine deposit (SW Turkey): architecture of a mixed clastic-carbonate succession

Abstract

The Ballik area (SW Turkey) was studied as a mixed clastic-continental carbonate reservoir analogue, in which kilometre wide and up to 70-m-thick tufa and travertine lithologies are found in an envelope of detrital sediments, which locally strongly interfinger with these porous carbonates. Former studies focussed on the carbonate lithologies, since they are considered as pre-salt analogues. This study aims to describe the adjacent non-carbonate lithologies, unravel their depositional setting, and address their influence on the overall sedimentary architecture. This study relies on an extensive field campaign, during which 142 samples of all different detrital lithologies were collected. Optical, fluorescence, cathodoluminescence, and Scanning Electron Microscopy (SEM) yielded important insights in the petrography of these lithologies, based on which 5 main lithologies were differentiated: i.e., (1) laminated marls, (2) polygenetic conglomerates, (3) massive marls, (4) tabular sandstones, and (5) coquina accumulations. These were interpreted to represent three different sedimentary facies corresponding to lacustrine, fluvial, and shoreline facies. The (clay) mineralogy of lacustrine sediments was extensively studied by bulk and clay-specific XRD. In this respect, special emphasis was laid on the depositional setting of the lacustrine facies, in which both authigenic palygorskite and poorly ordered dolomite were identified. Petrophysical properties of 16 plugs were determined by He porosimetry and N2-permeability, indicating that the detrital sediments are characterised by poor reservoir properties. The latter causes them to act, after assumed burial compaction, as potential barriers within a continental carbonate reservoir system.