Speleogenesis and depositional hystory of paleokarst phreatic caves/cavities; Podgrad, SW Slovenia

The studied palaeokarst corresponds to an uplifted peripheral foreland bulge when Upper Cretaceous diagenetically immature eugenetic carbonates were subaerially exposed, karstified and subsequently overlain by upper Paleocene/lower Eocene palustrine limestone. Among the subsurface paleokarstic features, both vadose and phreatic forms occur. The phreatic caves/cavities include features characteristic of the mixing zone speleogenesis at the interface between freshwater (brackish water) lenses and the underlying seawater. They were found in various positions with respect to the paleokarstic surface, the deepest being about 75 m below the surface. Three indistinct horizons of cavities/caves and intermediate vugs were recognized. Subsequently, all cavities were completely filled with detrital sediments and speleothems in the phreatic and vadose zones. In general, the phreatic cavities of the lower two horizons are geopetally filled with mudstone derived from incomplete dissolution of the host rock and overlain by coarse-grained, blocky calcite. Shallower below the paleokarst surface, a large phreatic cave of the third horizon is filled with flowstone overlain by reddish micritic carbonate sediment with intercalated calcite rafts. In the upper part of the cave, sediments derived from the paleokarst surface are gradually becoming more abundant. Vadose channels, which may also intersect the cave sediments, are mainly filled with "pedogenic" material derived from the paleokarst surface. Immediately prior to marine transgression over the paleokarst surface, some cavities were filled with marine-derived microturbidites. In general, the diversity of cave fills and the amount of surface material decrease with distance from the paleokarst surface. Below the paleokarst surface, the δ13C and δ18O values of a host rock and cavity deposits show good correlation with trends significant for meteoric diagenesis. It is shown that deposits associated with phreatic caves can be of great importance for the study of the speleogenetic, geomorphological and hydrogeological evolution of certain palaeokarst regions.

SEISMIC ATTRIBUTES AIDED DETECTION OF NW-SE TRENDING FAULTS DEVELOPED ON AN ISOLATED CARBONATE PLATFORM IN THE NW SIRTE BASIN, NORTH CENTRAL LIBYA

The lower and upper Paleocene reservoir formations, the primary producing formations in the northwest Sirte Basin, north-central Libya have complex structures which have an impact on the performance of the reservoirs. It is extremely crucial to understand the complex relationships between the fault networks and stratigraphy of the area for future field development. However, delineating faults particularly subtle faults is not an easy process due to the low signal-to-noise ratio in the post stack seismic data despite the effort and careful process of the pre-stack data. Seismic attributes are critical tools in detecting and enhancing major and minor fault interpretation beyond the seismic resolution of the conventional seismic dataset. This study utilizes variance, root mean square, and curvature attributes computed from the post-stack 3D seismic data acquired in the northwest Sirte Basin to detect major and minor faults along an isolated carbonate platform. A spectral whitening and median filter were applied to improve the quality of the data and remove random noise resulted from data acquisition and processing steps. Those methods were utilized to provide high-resolution seismic data and better show edges and structural features. Numerous faults have been detected in the study area. Most major faults in the lower and upper Paleocene reservoir formations are located along the margins of the isolated carbonate platform and have a NW-SE trend. Data conditioning and seismic attribute analyses applied on the 3-D seismic dataset effectively enhanced our understanding of the reservoir complexity and improve the detection of the major and minor faults and fracture zones in the study area.

FIRST RECORD OF CALCAREOUS GREEN ALGAE (DASYCLADALES, HALIMEDACEAE) FROM THE PALEOCENE CHEHEL KAMAN FORMATION OF NORTH-EASTERN IRAN (KOPET-DAGH BASIN)

The micropalaeontological inventory of the shallow-water carbonates of the Paleocene Chehel-Kaman Formation cropping out in the Kopet-Dagh Basin of north-eastern Iran is poorly known. New sampling has evidenced for the first time the occurrence of layers with abundant calcareous green algae including Dasycladales and Halimedaceae. The following dasycladalean taxa have been observed: Jodotella veslensis Morellet & Morellet, Cymopolia cf. mayaense Johnson & Kaska, Neomeris plagnensis Deloffre, Thyrsoporella-Trinocladus, Uteria aff. merienda (Elliott) and Acicularia div. sp. The studied section is devoid of larger benthic foraminifera and can be referred to the middle-upper Paleocene (SBZ 2-4) due to the presence of Rahaghia khorassanica (Rahaghi). Some of the dasycladalean taxa are herein reported for the first time not only from Iran but also the Central Neotethyan realm.

Petrographical and microfacies study of Sinjar formation in Bazyan anticline, Sulaimaniyah region (Northern Iraq)

Purpose. The work studies Sinjar formation (upper Paleocene lower Eocene) within the Bazyan anticline in the Sulaimaniyah region (northeastern Iraq). The facies analysis is based on the petrographic study of limestone deposits and is essential to identify their nature. The sediments that formed Sinjar formation have a high content of skeletal granules which include a small amount of red algae and residues of unicellular organisms-foraminifera. Methodology. The method of work included two main aspects: field study and laboratory work. The first part included the field description of the rocky excavation and modeling of 10 rocks samples from it within the Bazyan section. As for the second main aspect, it included the preparation of 10 slides for petrographic study of Sinjar Formation rocks followed by a facial analysis of these deposits. Findings. Micro facial analysis showed that the sequences of Sinjar formation consist of three main facies. The wacky limestone facies bears benthic foraminifera. The facies of compact limestone bears the benthic foraminifera and red algae while the compact wacky limestone facies bears the fossils. Originality. Wacky limestone facies bearing benthic foraminifera, compacted limestone facies bearing benthic foraminifera and red algae, and wacky limestone facies bearing benthic foraminifera were selected and studied. Thus, according to the facial analysis, Sinjar formation was deposited within the open shelf before the formation of the main deposit. Practical value. Samples of rocks were obtained from the Bazyan anticline for further production of slides in order to study the facies of this anticline, which allowed showing its lithostratigraphic column.

The History of Transgressions during the Late Paleocene-Early Eocene in the Kuqa Depression, Tarim Basin: Constraints from C-O-S-Sr Isotopic Geochemistry

The Tethys Sea extended into the Kuqa Depression from the Paleocene to the late Eocene and provided an abundant provenance for the deposition of evaporite sequences. Until now, detailed research on the history of transgressions during the late Paleocene-early Eocene in the Kuqa Depression has been limited. Therefore, in this study, we took the upper Paleocene Talak section and the lower Eocene Xiaokuzibai section in the western part of the Depression as the research objects and analyzed the petrology, the carbon and oxygen isotopes of carbonate rocks, and the sulfur and strontium isotopes of gypsum rocks to systematically study the above issues. The δ13C, δ18O and δ34S values of the upper Paleocene evaporite sequences were determined to be between 4.2‰ and 5.7‰, between −5.2‰ and 2.4‰, and between 16.5‰ and 17.9‰, respectively. The δ13C, δ18O, δ34S, and 87Sr/86Sr values of the lower Eocene evaporite sequences were determined to be between −6.9‰ and −2.0‰, between −9.0‰ and −4.5‰, between 10.5‰ and 17.0‰, and between 0.708642 and 0.709883, respectively. The analysis results show that the evaporite sequence of the upper Paleocene was formed by transgression. The deposition of the evaporite sequence changed from continental to marine deposition, and then gradually transitioned to continental during the Early Eocene. This paper is of great significance for reconstructing the history of transgressions in the Tethys tectonic realm during this period.

Geochemical Characterization and Thermal Maturation of Cerrejón Formation: Implications for the Petroleum System in the Ranchería Sub-Basin, Colombia

The Upper Paleocene Cerrejón Formation is a great source of coal in Colombia. The northeastern part of the Ranchería Sub-Basin sees the most intense mining activity. As a consequence, all geological studies have been concentrated on this region. Consequently, neither the distribution of the Cerrejón Formation, nor the quality and quantity of organic matter in the rest of the sub-basin is clear. In this study, we analyzed new geochemical data from Rock–Eval pyrolysis analyses and vitrinite reflectance using core samples from the ANH-CAÑABOBA-1 and ANH-CARRETALITO-1 wells. Based on this information, it was possible to classify the geochemical characteristics of the Cerrejón Formation as a source rock, particularly in the central area of the sub-basin, which had not been extensively studied before. Additionally, based on the interpretation of seismic reflection data, the numerical burial history models were reconstructed using PetroMod software, in order to understand the evolution of the petroleum system in the sub-basin. The models were calibrated with the data of maximum pyrolysis temperature (Tmax), vitrinite reflectance (%Ro), and bottom hole temperature (BHT). We infer the potential times of the generation and expulsion of hydrocarbon from the source rock.

A Paleocene vertebrate-bitten crocodilian coprolite from Liverpool Point, Maryland, U.S.A.

Although still exceedingly rare, the number of known vertebrate-bitten coprolites continues to increase. A vertebrate-bitten coprolite is herein reported from the Piscataway Member of the upper Paleocene Aquia Formation at Liverpool Point, Maryland, U.S.A.The specimen is described, figured, and chemically characterized by means of non-destructive hand-held energy dispersive X-ray fluorescence (HH-XRF). Four roughly parallel and evenly spaced gouges disrupt the surface of this compound ichnofossil. Many more much smaller markings, interpreted as feeding traces by smaller organisms (invertebrates or small actinopterygian fishes?), also ornament its surface. Whereas the studied coprolite can be identified most likely as the fossilized feces of a crocodilian, the identity of the vertebrate(s) that bit it remains unknown.

Sedimentary Cyclicity in the Upper Paleocene- Eocene Successions of the Haymana Basin (Ankara, Turkey): Responses of Fossils to Cyclicity

<p>The Haymana Basin in central Anatolia (Turkey) formed during the closure of the Neo-Tethys on Late Cretaceous to Middle Eocene as a forearc accretionary wedge. Late Paleocene to Middle Eocene aged units in this basin are exposed near Çayraz Village, Haymana. The Çayraz Formation is the youngest unit of the Haymana Basin, and it is represented by packages of nummulitic banks, and the intercalation of calcareous mudstones. The aim of this study is to investigate the sedimentary cyclicity and depositional sequences in the Upper Paleocene- Eocene successions of the Haymana Basin. To be able to achieve this objective, a stratigraphic section has been measured through this succession. In this study, detailed microfacies analyses of the shallow-water carbonate successions indicate a ramp type depositional model of the carbonate rocks. The facies composed of Alveolina sp., Orbitolites sp., and  Miliolids that indicate low energy depositional environment . After that depositional environment to  the shoal; the facies composed of Nummulites spp., Assilina spp. occur and increase their abundance towards high-energy environments. Absence of the Alveolina sp., Orbitolites sp., and Miliolids. occur in accordance with that. The facies composed of Nummulites spp., Assilina spp. become associated with Discocyclina sp. towards to open sea on the ramp, and the shallow open marine part is represented by the shale with the association of planktonic foraminifera. Lateral relationships of the facies from proximal (inner ramp) to the distal (mid ramp) part of the ramp are investigated by using the knowledge of paleoecology preferences of the fossils, lithologic data of the rocks and biological aspects of the fossils.  The fossil associations and their indicator environments can be used in vertical changes of the facies as in the lateral relationships of the facies. It has potential to derive cyclic relationships of the stratigraphic sequence. Therefore, based on the detailed microfacies analysis and change in the distribution of the fossil associations in the stacking pattern of the sequence, a composite depositional model has been suggested. At this part of the research newly acquired question is that the driven factor of these cyclic relationships of the sequence, whether it occurred by the control of the eustatic sea- level or the interplay between tectonics and the eustacy as the dominating factor in the sequence formation.</p><p> </p><p>Keywords: Large Benthic Foraminifera, Nummulites spp., Assilina spp., Haymana Basin, Çayraz Formation</p>