Clypeina lagustensis n.sp., a new calcareous alga from the Lower Tithonian of the Lastovo Island (Croatia)

Clypeina lagustensis n.sp. has been found in the Lower Tithonian deposits of the Lastovo Island (Dalmatia, Croatia). It is visually similar, obviously related and in some sections appearing almost identical, to Clypeina jurassica FAVRE, from which it differs by visible swellings and thinning of the central cavity, more pronounced distance between neighbouring whorls of fertile branches, and shape and structure of the interverticillate thallus parts, characterized by having well developed, hairy, sterile branches. These, after emerging from the exit pore, divide into several bundles which form a common turf with a calcareous envelope in the proximal part. Normal 0 21 false false false HR X-NONE X-NONE <!--[endif] --

Intrashelf basin record of redox and productivity changes along the Arabian margin of Neo-Tethys during Oceanic Anoxic Event 1a

The biotic, environmental, climatic, oceanic, and sea-level perturbations during the Early Aptian Oceanic Anoxic Event (OAE) 1a have been extensively documented from both deep- and shallow-marine deposits worldwide. However, there has been relatively little comparative assessment of the simultaneous interplay among organic carbon burial, redox conditions, terrigenous output, and productivity, leading to a lack of precise constraints on these relationships. Here, we use analyses of stable carbon isotopes (δ13Corg, δ13Ccarb, and Δ13C), total organic carbon (TOC), detrital proxies (Al, Si, Ti, K), redox-sensitive (RSTE: U, V, Mo) and productive-sensitive (PSTE: P, Cu, Ni) trace elements from a continuous, predominantly carbonate succession of the Kazhdumi Intrashelf Basin to evaluate the culprits for the OAE1a-associated changes in bottom-water oxygenation, organic-rich layer formation, and biotic shifts along the Arabian margin of the Neo-Tethys. Concentrations of Al-normalized RSTE and TOC values indicate that the bottom water conditions ranged from oxic prior to and at the onset of the OAE 1a (carbon-isotope segments C2 to basalmost C4 sensu Menegatti et al., 1998), to anoxic-suboxic but not euxinic (Mo 100 m), continental-margin basins during major oceanic perturbations

A brief insight into the Upper Triassic to Miocene sedimentary succession of the External Dinarides, SE of Dubrovnik (southern Croatia)

The Konavle area located in the very southeast of the Republic of Croatia encompasses a large part of the entire External Dinarides sedimentary sequence, almost 5 km in thickness. It consists of two geologically and geomorphologically different parts, the Donja Banda and the Gornja Banda, separated by one of the most significant faults in the Dinarides, the so-called High Karst Nappe, which divides two regional tectonic units: the less disturbed Adriatic or Dalmatian Zone to the SW and the intensely deformed High Karst Unit to the NE. The Donja Banda as a part of the Dalmatian Zone is composed of Upper Cretaceous carbonates and Palaeogene carbonate and clastic deposits. The Gornja Banda as a part of the High Karst Unit represents a thick sequence of Upper Triassic, Jurassic and Lower Cretaceous carbonate deposits monoclinally inclined towards the SE, passing into Bosnia and Herzegovina where the younger Cretaceous and Palaeogene deposits crop out. The first part of the field trip includes three stops in the Gornja Banda area, with a detailed elaboration of the deposition of shallow-water deposits of the older part of the AdCP. It comprises upper Toarcian–lower Aalenian coated-grain dominated carbonates, upper Kimmeridgian shallow subtidal and peritidal facies with subaerial exposure breccias, and uppermost Tithonian peritidal, laminite-capped cycles with dasyclads and faecal pellets. The second part presents some typical examples of the Upper Cretaceous carbonates and Palaeogene carbonate and clastic deposits of the Konavle region, in order to place them in the regional context of the evolution of the AdCP and External Dinarides. It comprises the oldest Upper Cretaceous rocks in the area, the Santonian–Campanian Gornji Humac fm. and a brief overview of the recent seismicity of the Dubrovnik region, Maastrichtian limestones representing the top of the Cretaceous, Palaeocene(–lower Eocene?) carbonates marking the end of the Adriatic Carbonate Platform in Konavle, Eocene Foraminiferal limestones, Palaeogene clastic deposits and a visit to Medieval fortress of Sokol Grad

A brief insight into the Upper Triassic to Miocene sedimentary succession of the External Dinarides, SE of Dubrovnik (southern Croatia)

The Konavle area located in the very southeast of the Republic of Croatia encompasses a large part of the entire External Dinarides sedimentary sequence, almost 5 km in thickness. It consists of two geologically and geomorphologically different parts, the Donja Banda and the Gornja Banda, separated by one of the most significant faults in the Dinarides, the so-called High Karst Nappe, which divides two regional tectonic units: the less disturbed Adriatic or Dalmatian Zone to the SW and the intensely deformed High Karst Unit to the NE. The Donja Banda as a part of the Dalmatian Zone is composed of Upper Cretaceous carbonates and Palaeogene carbonate and clastic deposits. The Gornja Banda as a part of the High Karst Unit represents a thick sequence of Upper Triassic, Jurassic and Lower Cretaceous carbonate deposits monoclinally inclined towards the SE, passing into Bosnia and Herzegovina where the younger Cretaceous and Palaeogene deposits crop out. The first part of the field trip includes three stops in the Gornja Banda area, with a detailed elaboration of the deposition of shallow-water deposits of the older part of the AdCP. It comprises upper Toarcian–lower Aalenian coated-grain dominated carbonates, upper Kimmeridgian shallow subtidal and peritidal facies with subaerial exposure breccias, and uppermost Tithonian peritidal, laminite-capped cycles with dasyclads and faecal pellets. The second part presents some typical examples of the Upper Cretaceous carbonates and Palaeogene carbonate and clastic deposits of the Konavle region, in order to place them in the regional context of the evolution of the AdCP and External Dinarides. It comprises the oldest Upper Cretaceous rocks in the area, the Santonian–Campanian Gornji Humac fm. and a brief overview of the recent seismicity of the Dubrovnik region, Maastrichtian limestones representing the top of the Cretaceous, Palaeocene(–lower Eocene?) carbonates marking the end of the Adriatic Carbonate Platform in Konavle, Eocene Foraminiferal limestones, Palaeogene clastic deposits and a visit to Medieval fortress of Sokol Grad

Microfacies, depositional environment and diagenetic evolution controls on the reservoir quality of the Permian Upper Dalan Formation, Kish Gas Field, Zagros Basin

© 2015 Elsevier Ltd. The Upper Permian Upper Dalan Formation contains one of the largest gas reservoirs in the world. The formation consists of carbonates with some evaporite intercalations that developed on a gently sloping homoclinal carbonate ramp facing the Late Permian Paleo-Tethys Ocean. This study focuses on the Kish Gas Field (Zagros offshore basin situated between Iran and Qatar), and is based on a 222-m-thick continuous core. Based on the integration of core- and wireline-log data coupled with petrographic analyses of 580 thin sections, three major depositional environments (facies belts) with 11 carbonate microfacies are identified. These include (1) sabkha to tidal flat (laminated to massive anhydrite, dolomudstone with anhydrite nodules, dolomudstone, and intraclastic dolowackestone), (2) lagoon and leeward shoals (bioclastic wackestone/dolowackestone to packstone, and peloid dolopackstone and peloid-bioclastic dolopackstone), and (3) mobile (windward) sand shoal (ooid-peloid dolograinstone, ooid dolograinstone, ooid-intraclast dolograinstone, ooid-bioclast dolograinstone-packstone, and coarse bioclast-intraclast dolograinstone). Diagenetic evolution of the Upper Dalan Formation is associated with evaporative marine, shallow-water normal-marine, meteoric, and burial diagenetic environments. Common diagenetic effects include dolomite and calcite cementation, mechanical and chemical compaction, dissolution, dolomitization, and evaporative (anhydrite) mineralization. Reservoir quality is strongly affected by variations in the original rock fabrics and subsequent diagenetic alterations. The most common pore types include interparticle, moldic, and connected vug (fracture and cavernous). The interparticle porosity-permeability relationship for the studied facies suggests that the reservoir quality is not affected by different crystal sizes and most samples plot in the low porosity and low to high permeability field, or display Lucia class 1 or 2 petrophysical relationships. The study shows that the pervasive pore-filling anhydrite mineralization lead to a significant decrease in porosity and permeability; poikilotopic anhydrite cement reduced matrix porosity, but the pore size was less affected.status: publishe