ENVIRONMENTAL GEOLOGY 2017
Results and discussion 2
Lithofacies associations (LFA) and depositional model
Facies types were grouped into lithofacies associations (LFA) based on their interpreted depositional environment on the carbonate platform. Table 3 lists the names and characteristics of these lithofacies associations. From the previous data, a 2D depositional model for the inner ramp part of a platform with facies types and related depositional/lithofacies associations for the investigated area of the Miocene outcrop sections was done (Fig. 5).
Sequence stratigraphy
The interpreted lithofacies types are stacked into facies sequences of multiple hierarchies. Based on the approach of Kerans and Tinker (1997), three orders of cycles were distinguished. Cycles of small-scale order form cycle sets of medium-scale order which finally arranged in sequences (large-scale cycle). The most significant vertical changes within these successions are sedimentary texture, grain size and biocomponent. The described cycles,cycle sets and sequences were subdivided into transgressive and regressive parts. They are separated by turnarounds, i.e. zones of maximum and minimum accommodation (Cross and Lessenger, 1998).
Small-scale cycles
Restricted ramp cycle type
The thickness of this rather asymmetrical cycle type ranges in 122 thickness from 3 to 5 m (Fig. 6). The main distribution of this cycle is apparently restricted on S1 and S2 at the three studied sections. The lower part of this cycle varies from 1.25 to 4.5 m thick, consists mainly of brownish gray, moderately compact, thinly laminated, jointed, unfossiliferous, ferruginous, gypsiferous, with gypsum bands and veins (up to 2 cm thick), very slightly calcareous (LFT 1a). The vertical thickness of the upper part ranges 1in thickness from 0.25 to 0.75 m and consists of yellowish brown, moderately sorted and compact calcareous sandstone, with few feldspar minerals and pelcypod fragments (LFT 2a).The lower part could be interpreted as low energy proximal peritidal facies types forming a regressive hemi-cycle. The sequence boundary is marked by change in facies from shale sediments to bioclastic sandstone. The transgressive hemi-cycle could be interpreted as a retrogradation of more distal, tidal flat facies association over the peritidal strata.
