2.2.4. Paleocene-Eocene Limestones

This formation also known as "Limestones with microbreccia" [75] is characterized by the same sedimentary facies with the underlying formation, with prominent microbreccia derived from the erosion of Cretaceous carbonates from both the Gavrovo (to the east) and Apulian (to the west) platforms. On Late Paleocene and progressively through the Early Eocene, the supply of calciclastic material diminished significantly, especially in the central Ionian Basin. The main depositional facies during the Eocene were platy wackestone and mudstone with Globigerinidae and chert nodules, analogous to those of the Vigla Limestones, but lack continuous siliceous intervals [34].

## **3. Materials and Methods**

Six sections (A–F; Figure 2A–E) were sampled every 1 m and studied in terms of their reservoir parameters, paleodeposition environment, and paleogeographic significance.

Section A (Agios Georgios Section) is situated at the entrance of Agios Georgios village (lat: 39◦16′14.99" N, lon: 20◦50′59.43" E; Figure 2B). This section belongs to the Pantokrator Limestones (Figure 3), with a total length of 50 m, where 50 samples have been collected (Figure 4).

Section B (Perivleptos section) is situated at the north part of Perivleptos village (lat: 39◦46′21.90" N, lon: 20◦46′48.34" E; Figure 2C). This section covers parts of Pantokrator Limestones and Vigla Shales (Figure 3). The total length of the section is 20 m, where 20 samples have been collected (Figure 4).

Section C (Vigla Section) is situated at the south part of Asprageli village (lat: 39◦48′33.45" N, lon: 20◦43′38.73" E; Figure 2D). This section covers partially the Vigla Limestones (Figure 3) with a total length of 20 m, where 20 samples have been collected (Figure 4).

Section D (Koloniati section) is situated at the north part of Koloniati village (lat: 39◦34′52.46" N, lon: 20◦53′11.41" E; Figure 2E). This section covers the upper part of the Vigla Limestones and the lower part of the Senonian Limestones, which are separated by an unconformity (Figure 3). The total length of the section is 60 m, where 30 samples have been collected every 2 m (Figure 4).

Section E (Asprageli-2 Section) is situated at the north-east part of Asprageli village, near the section C (lat: 39◦49′54.00" N, lon: 20◦43′58.25" E; Figure 2D). This section covers the Senonian Limestones (Figure 3), with a total length of 10 m, where 10 samples have been collected (Figure 4).

Section F (Asprageli-1 Section) is situated at the north-east part of Asprageli village (lat: 39◦45′57.42" N, lon: 20◦43′58.25" E; Figure 2D). This section covers the part of Paleocene-Eocene limestones (Figure 3), with a total length of 25 m, where 25 samples have been collected (Figure 4).

**Figure 3.** Synthetic lithostratigraphic column of the Ionian zone (modified from [34]), along with the correspondence of study sections stratigraphy with Ionian formations and their average porosity values as potential reservoir rocks. The colors in the lithostratigraphic column are consistent with the relevant colors of the International Chronostratigraphic Chart (v2020/01). (1) Shales and sandstones; (2) limestones with rare cherty intercalations, occasionally microbreccious; (3) pelagic limestones with clastic platform elements; (4) pelagic limestones with cherts; (5) cherty beds with shale and marl intercalations; (6) pelagic limestones with cherty nodules and marls; (7) pelagic limestones with bivalves; (8) pelagic, nodular red limestones with ammonites; (9) marly limestones and laminated marls; (10) conglomerates-breccias and marls with ammonites; (11) pelagic limestones with rare cherty intercalations; (12) external platform limestones with brachiopods and small ammonites in upper part; (13) platform limestones; (14) thin-bedded black limestones; (15) evaporites; (16) shales.

**Figure 4.** Lithology of the 6 study sections in Epirus region. The orange and blue circles at the right of each column represent the sampling intervals for thin sections as well as porosity and bulk density measurements.

The study of the Jurassic to Eocene sediments' distribution was based on tectonic, stratigraphic, paleontologic, and sedimentologic observations. Depending mostly on outcropping conditions, an average sampling interval of approximately 1 m has been used. An overall number of 150 samples were collected, among which 70 used for sedimentary facies analysis and 50 for measuring porosity and bulk density. Microfacies definition and textural characters analysis of the carbonate rocks, including both biogenic and inorganic dominant components, were done according to carbonate classification schemes of [77], which later modified by [78], based on the Standard Microfacies Types (SMF) in the facies zones (FZ) of the rimmed carbonate platform model. Depositional environments were reconstructed based on the derived sedimentological features and through comparison with additional standard facies reconstructions [79–85]. Therefore, assemblages consisting of several SMF types characterize all depositional environments. Thin sections were prepared in the Historical Geology and Paleontology Laboratory (National and Kapodistrian University of Athens; NKUA), biostratigraphically and sedimentologically studied under a polarized LEICA DM LP microscope, and photos have been performed with OLYMPUS UC30 Microscope Digital Camera. The reservoir potential of these carbonates was also obtained through the examination of porosity and bulk density parameters on representative of each stratigraphic formation samples, with the use of GeoPyc 1360 Envelope Density Analyzer and helium AccuPyc 1330 Pycnometer, respectively, also at NKUA. All measurements were made on dry samples that were previously dried in the oven at 40 ◦C for 24 h. The petroleum potential information was further compared with existing regional data covering the studied stratigraphic interval. Finally, ArcGIS software was used to visualize the results of the study area, along with additional data known from the literature, outcropped and well data [33,35,42,59,86] expanding the entire Ionian zone within paleogeographic/paleoenvironmental maps for the relevant time interval.
