Ichnofossils from the Miocene Middle Bhuban Formation, Mizoram, Northeast India and their Paleoenvironmental Significance

An ichnofossil assemblage is preserved in sediments of the Middle Bhuban Formation, Surma Group, of Miocene age from the Durtlang and Chanmari sections, Aizawl district, Mizoram, northeastern India. The studied sections comprise a thick, bioturbated and thinly bedded sandstone-silty shale facies. The preserved ichnofossils show high density and low diversity with the assemblage represented by feeding and resting traces, i.e., Psilonichnus upsilon Frey et al., 1984, Ophiomorpha isp., Teichichnus spiralis Mikulas. 1990, Skolithos isp., Palaeophycus isp., and other horizontal burrows. Sedimentary structures associated with these traces are mainly cross bedding, flaser bedding and slump structures. Considering the distribution of the Psilonichnus ichnogenus across an integrated ichnological-sedimentological framework, the stratigraphic interval of the Middle Bhuban Formation, in which they occur, are interpreted to have been deposited under a shallow, marginal-marine channel complex dominated by tidal channels developed in quiet, brackish-water portions of a delta plain.

Microfacies models and sequence stratigraphic architecture of the Oligocene-Miocene Qom Formation, south of Qom City, Iran

The Oligocene-Miocene Qom Formation has different depositional models in the Central han, Sanandaj-Sirjan and Urunlieh-Dokhtar inagmatic arc provinces in han. The Kahak section of the Qom Formation in the Uiumieh-Dokhtar magmatic arc has been studied, in order to determinate its microfacies, depositional model and sequence stratigraphy. The textural analysis and faunal assemblages reveal ten microfacies. These microfacies are indicative of five depositional settings of open marine, patch reef, lagoon, tidal flat and beach of the inner and middle ramp. On the basis of the vertical succession architecture of depositional system tracts, four third-order sequences have been recognized in the Oligocene-Miocene Kahak succession of Qom Formation. Based on the correlation charts, the transgression of the Qom Sea started fiom the southeast and continued gradually towards the north. This resulted in widespread northward development of the lagoon paleoenvironment in the Aquitanian-Burdigalian stages. Also, the sequence stratigraphic model of the Oligocene Miocene Qom Formation has an architecture similar to those that have developed from Oligocene Miocene global sea level changes.

Sedimentologic Study of Miocene Outcrops-Ouenza in Algero-Tunisian Frontiers

The results of the granulometrical and sequential analysis supported by micropaleontological dating using the foraminifera as well as chemico-ponderous and X-ray diffraction analysis,confirmed the contemporaneity of the Burdigalian outcrops of the two studied zones(Ain Sidi Salah zone in the northeast and Fedj El Behim zone in the southwest), both located at the north of the city of Ouenza in

Changes in Calcareous Nannofossil Assemblages and Paleoenvironmental Interpretation of the Early Miocene Lice Formation, Kahramanmara? Basin, Turkey, East Mediterranean

This study investigated the calcareous nannofossil assemblages in detail from the early Miocene aged Lice Formation outcropping in the Kahramanmara? basin. The biostratigraphy of calcareous nannofossils was outlined and paleoenvironmental features determined. In 81 samples taken from three measured sections in the region, 17 calcareous nannofossil genus and 48 nannofossil species were identified. These calcareous nannofossil genus and species identified the Lice Formation as being in the CNM4 nannofossil biozone. The abundance and diversity of early Miocene calcareous nannofossil species varied in the measured sections, with the samples generally moderate-poor, apart from a few samples. The relative abundance of individuals of Cyclicargolithus floridanus, Coccolithus pelagicus, Reticulofenestra hagii and Sphenolithus moriformis species, with paleoecological importance identified in the study region, indicate that in early Miocene times, the basin in which the Lice Formation deposited was meso-eutrophic with excess nutrient input, temperate and generally stable shallow marine conditions.