Yuruma Formation (Barremian - lower Aptian?) In the Yuruma hill and Punta Espada, Alta Guajira, Uribia, Colombia

The Yuruma Formation in the Yuruma hill area its type locality can be differentiated into two stratigraphic intervals. The lower and upper intervals of the Yuruma Formation can also be subdivided into two segments. The lithological, sedimentological and fossiliferous characteristics support this differentiation, which allows to interpret the accumulation energy influences over the sea floor. The lower interval is characterized by intercalations of very fossiliferous marlstones and biomicrites with benthonic and nektonic fossils from the lower Barremian. The upper interval is represented by marlstones and biomicrites with poor benthonic and nektonic fossils from the upper Barremian and probably from the lower Aptian. In the Punta Espada area, whit scarce lithological controls over the lower and upper parts of the Yuruma Formation, were found biomicrites with benthonic and nektonic fossils of the lower Barremian to the lower part, and to the top were recognized biomicrites that underlie beds with lower Aptian ammonites.

Upper Barremian–lower Aptian scleractinian corals of central Europe (Schrattenkalk Fm., Helvetic Zone, Austria, Germany, Switzerland)

From the Schrattenkalk Formation (upper Barremian–lower Aptian) of southern Germany, western Austria, and Switzerland, new coral material is taxonomically described, belonging to 56 species from 35 genera of 21 families: Actinastrea pseudominima (Koby); A. subornata (d’Orbigny); Paretallonia bendukidzeae Sikharulidze; Eugyra (Felixigyra) crassa (de Fromentel) (new combination); E. (F.) patruliusi (Morycowa); E. (F.) picteti (Koby) (new combination); E. rariseptata Morycowa; Myriophyllia propria Sikharulidze; Thecosmilia dichotoma Koby; Clausastrea plana (de Fromentel); Complexastrea cf. lobata Geyer; Paraclausastrea chevalieri Zlatarski; P. kaufmanni (Koby); P. vorarlbergensis Baron-Szabo; ?Montlivaltia sp.; Diplogyra subplanotabulata Sikharulidze; Hydnophora styriaca (Michelin); Dermosmilia fiagdonensis Starostina & Krasnov; D. cf. laxata (Étallon); D. trichotoma Eguchi; D. tuapensis Baron-Szabo & Gonzalez.-León; Placophyllia grata Bugrova; Cairnsipsammia merbeleri Baron-Szabo; Morphastrea ludovici (Michelin) (emended herein); Ahrdorffia ornata (Morycowa); Astraeofungia tirnovoriana (Toula) (new combination); Actinaraea (Camptodocis) brancai (Dietrich); A. tenuis Morycowa; Rhipidomeandra bugrovae Morycowa & Masse; Comoseris aptiensis Baron-Szabo; Comoseris jireceki Toula; Polyphylloseris mammillata Eguchi; Ellipsocoenia barottei (de Fromentel) (new combination); Ellipsocoenia haimei (de Fromentel) (new combination); Dimorphastrea tenustriata de Fromentel; Latomeandra cf. plicata (Goldfuss); Microphyllia gemina Eliášová; Thalamocaeniopsis stricta (Milne Edwards & Haime)(new combination); Trigerastraea haldonensis (Duncan) (new combination); Heliocoenia rozkowskae Morycowa; H. vadosa (Počta); Stylosmilia corallina Koby; Cyathophora decipiens ramosa (Hackemesser) (new combination); C. mirtschinkae Kuzmicheva; Cladophyllia clemencia de Fromentel; C. conybearei Milne Edwards & Haime; C. crenata (Blanckenhorn); C. furcifera Roemer; C. rollieri (Koby); C. stutzi (Koby) (new combination); Amphiaulastrea conferta (Ogilvie); A. rarauensis (Morycowa); Heterocoenia inflexa (Eichwald); H. minima d’Orbigny; Acanthogyra aptiana Turnšek; as well as the new species Columnocoenia falkenbergensis. In addition, all the information about previously described taxa from the Schrattenkalk was evaluated with regard to their taxonomic assignment, stratigraphic and paleogeographic distribution, and paleoenvironmental relationships to faunas from other geographic areas and time periods. A total of 122 species belonging to 53 genera and 24 families are recognized from Schrattenkalk localities (western Austria, southern Germany, Switzerland). These include the taxa of both the Lower and Upper Schrattenkalk, and the intercalated Rawil Member. The Schrattenkalk coral fauna nearly exclusively consists of colonial forms of three general categories of polyp integration: cerioid-plocoid (33.6%); branching (18%); and (hydno-) meandroid-thamnasterioid (46.7%). Only two specimens were doubtfully assigned to solitary taxa. Corallite diameters range from less than 1 mm to over 20 mm and fall into three major corallite-size groups: small (up to 2.4 mm), medium (>2.4–9.5 mm), and large (>9.5 mm). The fauna is distinctly dominated by forms with medium-size corallites (68%), followed by forms having small-size corallites (26%). Together with the potential solitary taxa, corals with large-size corallites are of minimal importance to the total fauna. On the genus-level, the Schrattenkalk corals show closest affinities to coral assemblages of central (especially France; 55%), eastern and southern Europe (44‒49%), as well as Central America (47%). On the species-level, closest affinities are to coral assemblages of central, southeastern, and eastern Europe (16‒25.5%), as well as Central America (14%), but nearly a third of the Schrattenkalk species (30%) was restricted to the upper Barremian–lower Aptian of the Schrattenkalk Formation; this suggests that the Schrattenkalk platform sensu lato was a diversity center and a crucial reservoir for coral recruitment. The majority (86%) of the Schrattenkalk corals thrived in a shallow-water, reefal to perireefal, subtropical marine environment. In general, the Schrattenkalk coral assemblages are characteristic of moderate- to high-energy environments of the inner shelf to shore zone, having morphotype associations that typically prevail down to 10–15 m depth. In contrast, for the Upper Schrattenkalk coral fauna of central Switzerland (Hergiswil), a non-reefal paleoenvironment at a depth of several tens of meters is suggested by the morphotypes of the taxa and types of microfacies present. The corals of the Schrattenkalk Formation occurred in both photozoan (Lower and Upper Schrattenkalk members) and heterozoan (Rawil member) carbonate-producing communities. With regard to taxonomic diversity, the Schrattenkalk coral fauna is comparable to the most species-rich Upper Jurassic reef assemblages and represents the last major coral-reef development of the Mesozoic.

Criteria for petroleum potential and forecast of oil and gas prospective zones in the Achimov deposits of the Gydan Peninsula

The structure and seismogeological characteristics of the Achimov strata of the Gydan Peninsula are considered. Geological and geophysical criteria for the regional forecast of oil and gas potential, taking into account the clinoform structure of the Berriasian-Lower Aptian deposits, are proposed. Based on the interpretation of drilling data and 2D seismic exploration, predictive maps of the thickness of sand bodies were constructed, depocenters of accumulation of sandy material were mapped. Seismostratigraphic studies, which are based on a comprehensive analysis of the wave pattern of time seismic sections, dynamic and seismic facies analyzes, as well as paleotectonic and paleogeomorphological reconstructions, made it possible to identify the Salmanovskaya and Yuzhno-Gydanskaya oil and gas zones in the Achimov strata of the Gydan Peninsula.

Sequence stratigraphic framework of the mid-Cretaceous nonmarine Potomac Formation, New Jersey and Delaware

ABSTRACT We developed a sequence stratigraphic framework for the (Barremian to lower Cenomanian) fluvial–deltaic (primarily delta plain) Potomac Formation in the Medford, New Jersey, Fort Mott, New Jersey, and Summit Marina, Delaware coreholes. Previous studies have correlated distinctive lithologic units with attendant pollen zones and identified tentative sequence boundaries between lithologic units I (Barremian to lower Aptian, pollen Zone I), II (Aptian to lowermost Cenomanian, pollen Zone II), and III (lower Cenomanian, pollen Zone III) at all three sites. Here, we further subdivide these units into packages known as fluvial aggradation cycles (FACs). An analysis of FAC stacking patterns reveals potential sequence boundaries and systems tracts. FACs indicate that major lithologic unit boundaries are also sequence boundaries, indicate tentative higher-order sequence boundaries, and provide potential additional correlative surfaces among Potomac Formation sites. Our study demonstrates the applicability of the FAC method to identify stacking patterns and sequence stratigraphic surfaces in fluvial–deltaic deposits and demonstrates that FACs are excellent tools to decipher the difficult-to-correlate surfaces.