Asian Journal of Earth Sciences
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Open Access journal
ISSN (Print) 1819-1886 - ISSN (Online) 2152-3509
Published by Science Alert [52 journals] [SJR: 0.209] [H-I: 4]
- Depositional Evolution and Sediment Facies Pattern of the Tertiary Basin
in Southern Zagros, South Iran
Abstract: Succession of tertiary strata in the Hormozgan province of southern Iran consists of predominantly carbonate deposits and characterized by marked changes in facies and thickness. These changes relate to sediment deposition in a foreland basin along the NE margin of the Arabian plate. In this study, stratigraphic evolution, microfacies are used to constrain the depositional evolution of the Tertiary sediments. The succession was measured at four outcrop and wells sections in the East Khamir, West Khamir, Namak and West Namak anticlines. The age of the base of the succession is Paleocene and its upper part is probably late Oligocene. The lower of the succession consists of interbedded wackestone to packstones of the Pabdeh formation. These strata are overlain by up to intrashelf deposit altered packston to grainstone (Jahrum formation) that may represent much of late Paleocene-Eocene time. The upper part of the Jahrum formation overlain by carbonate platform deposit (Asmari and Razak formations). We argue that the lithofacies and sediment- accumulation history of this succession based on these regional profiles, the tertiary depositional history of the Bandar Abbas area was reconstructed and can be divided into two tectono-sedimentary phases suggesting a transition from an active to a passive margin. The active phase (late Paleocene) dominated by pelagic marls, gravity flow deposits and lateral thickness variations. During passive phase dominated by Shallow-water facies consist mainly of packstones to grainstone with abundant benthic foraminifera. Rapid variations in thickness, Sequence stratigraphy and facies document the evolution of depositional processes in the foreland basin. In the study area, the foreland basin is characterized by a considerable SW to NE increase in stratigraphic thickness.
PubDate: 28 May, 2014
- Ichnology of the Enugu Formation: Implications for Campanian Sea Movements
in Southeastern Nigeria
Abstract: Trace fossils from the outcrop section of the Enugu Formation in Anambra Basin, southeastern Nigeria, have been studied based on the varieties, types, mode of occurrence, orientation of the burrows, wall structures and fills. Five ichnogenera identified belong to the Skolithos and Cruziana ichnofacies and include; Skolithos isp. Thalassinoides isp., Planolites isp., Teichichnus isp. and Chondrites isp. The assemblage is suggestive of deposition in a nearshore setting influenced by stressed environmental conditions due to the mixture of marine and fresh water inflows. The lithologic characteristics, physical sedimentary structures, the distribution and the style of the bioturbation from the base to the top of the sequence, as well as the general absence of deeper marine ichnofacies suggest moderate to high energy conditions in a prograding shoreline and shallow marine environments.
PubDate: 28 May, 2014