Application of Facies Associations, Integrated Prediction Error Filter Analysis, and Chemostratigraphy to the Organic-Rich and Siliceous Cenomanian-Turonian Sequence, Bargou Area, Tunisia: Integrated Sequence Stratigraphic Analysis
Facies associations, integrated prediction error filter analysis (INPEFA) of spectral Gamma-ray data, Sr/Ca and Mn chemostratigraphy, and sequence stratigraphy of the organic-rich and siliceous Cenomanian-Turonian Bahloul formation have been studied in Bargou section, located in north-central Tunisia. The studied section is subdivided into seven facies evolving from platform to basin deposits. Based on basin geometry, facies distribution, spectral Gamma-ray INPEFA curves, Sr/Ca and Mn profiles patterns, and the sequence was also subdivided into shelf margin wedge (uppermost Fahden Formation-lowermost Bahloul), basal transgressive systems tract (remainder Bahloul Formation) and early high-stand systems tract (Kef Formation). The Sr/Ca ratios, Mn profile, sequence stratigraphic, and cyclostratigraphic interpretations reveal the existence of four transgressive parasequences deposited throughout 420？kyr within the organic rich and siliceous Bahloul facies. 1. Introduction The evolution of the sedimentary basins, which are considered to be filled by successive depositional sequences has proved and justified the use of the application of sequence stratigraphy concepts. The burial history of the sedimentary basin is panoply of several related factors such as subsidence, local tectonics, eustatic fluctuations, carbonate production, climatic cyclicity, as well as chemical reactions issued from several factors (temperature, pressure, density, etc.). These depositional sequences are subdivided further into systems tracts and parasequences [1–3]. The stratigraphy and sedimentology of the upper Cenomanian-lower Turonian Bahloul Formation in north-central Tunisia (Figure 1) have been the subject of numerous papers and reports (e.g., [4–8]). Recently, the recognition of the effects of sea-level changes on the stratigraphic successions led to the reinterpretation of the depositional sequences by Robaszynski et al. [9] and Maamouri et al. [10]. The main sequence (Bahloul formation) is typically controlled by the global relative sea-level rise causing the major latest Cenomanian transgression which in turn was interpreted as a combined phenomenon between a long-term sea-level rise and basin subsidence [1, 11, 12]. It must be understood that this sequence seems to be generated by enhanced plate tectonic activity and by the change in the Milankovitch frequency band (e.g., [13]) justifying climatic cycles which are detected in the sedimentary record (Figure 2). The major rise in the Cenomanian sea level was interrupted by the five-third order relative sea-level falls [1].
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