Sedimentary Facies Analysis, Reservoir Characteristics and Paleogeography Significance of the Early Jurassic to Eocene Carbonates in Epirus (Ionian Zone, Western Greece)

Abstract

Sedimentological, micropalaeontological, and marine geological results from the Early Jurassic to Eocene carbonate formations of the Ionian zone, from six localities of Epirus, provide new insights into the basin palaeogeographic evolution and better correlation with coeval analogous tectono-stratigraphic successions along the southern margin of the Neo-Tethys Ocean. Facies analysis allowed the recognition of several microfacies types and their depositional characteristics. During the Early Jurassic, autochthonous carbonates (Pantokrator Limestones) were deposited in shallow-water environment. The overlying (hemi)pelagic Siniais or their lateral equivalent Louros Limestones were deposited to the basin borders and mark the general deepening of the Ionian domain. During Toarcian to Tithonian, the Ionian Basin was characterized by an internal differentiation in small sub-basins with half-graben geometry presenting abrupt thickness and facies changes. The deeper parts were characterized by continuous sedimentation, while the elevated parts were marked by unconformities. The Early Cretaceous marks the homogenization of sedimentation by the deposition of the pelagic Vigla Limestones all over the Ionian zone. The transition from the Early to Late Cretaceous records a significant carbonate diversification in terms of biota assemblages, and related mineralogy due to intense tectonic activity in the region. From Late Cretaceous to Paleogene, allochthonous carbonates were transported to the outer shelf by turbidity currents (calciturbidites) and/or debris flows (limestones with breccia) formed by the gravitational collapse of the platform margin. Additional porosity and bulk density measurements showed that petrophysical behavior of these carbonates are controlled by the depositional environment and further influenced by diagenetic processes. The partly dolomitized neritic Jurassic carbonates, but mainly the Senonian calciturbidites and the microbrecciated Paleocene/Eocene limestones display the higher average porosity values, and therefore present enhanced carbonate reservoir quality.

Re-Evaluation of the Ionian Basin Evolution during the Late Cretaceous to Eocene (Aetoloakarnania Area, Western Greece)

“…The thickness variations across the basin are due to the tectonic shredding, and so different basin depths are observed. The Upper "Posidonia shales" represent the deposition during the Callovian-Kimmeridgian interval [2,18,20].…”

“…This Formation consists of thin-bedded pale limestones with nodules or lenses of chert alternating between chert and dark grey to green or red shale intercalations. The upper part of the sequence was deposited on top of the Lower Cretaceous "Vigla limestones" Formation, which is represented by the Upper Cretaceous "Senonian limestones" Formation (Coniacian to Maastrichtian) [2,3,16,18,19] (Figure 2).…”

“…The main Ionian zone, in general, has been studied by Aubouin [7], IGRS-IFP [8], Bornovas [9], Bernoulli and Renz [10], BP [11], Karakitsios and Tsaila Monopolis [12], Karakitsios et al [13], Skourtsis-Coroneou et al [14] and Zelilidis et al [3,15]. Nevertheless, only a few studies have dealt with microfacies analysis combined with the overall architecture of the depositional system of the Ionian basin [16][17][18][19]. Specifically, according to Karakitsios [2,20] and Zelilidis et al [3] the depositional system of the Ionian basin was subdivided into three successions: the pre-rift succession, consisting of lower to middle Triassic evaporites and Upper Triassic to Lower Jurassic limestones, the syn-rift succession, consisting of Lower to uppermost Jurassic deposits and the post rift succession, consisting of Cretaceous to Eocene deposits, and which was further subdivided into two sub-stages, the Lower Cretaceous and the Upper Cretaceous to the lower Eocene sub-stage, respectively.…”

Climate Change and Marine Geological Dynamics

“…The book Climate Change and Marine Geological Dynamics includes nine contributions [1][2][3][4][5][6][7][8][9] to this Special Issue published during 2020-2021. Overall, the aim of this Special Issue is to collect studies that provide new views on marginal and open marine geological phenomena and processes by using different methodologies and approaches.…”

“…A brief overview of all the contributions, emphasizing the main investigation topic and the outcome of the analysis follows. Kontakiotis et al (2020) [1] investigate the Mesozoic-Paleogene depositional history and paleogeographic evolution of marine biogenic carbonates in the western segment of the southern Tethys (Ionian basin, Epirus, Greece). This integrated sedimentological, micropaleontological and stratigraphic study is based on lithostratigraphic characteristics, facies analysis and reservoir petrophysical behaviors of the carbonate successions, in conjunction with a synthetic paleogeographic reconstruction.…”