Paleontology of the Jurassic Calcareous Unit at Sheket Section, Mekelle Basin, Northern Ethiopia
No Thumbnail Available
Date
2024-06
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa University
Abstract
The Mesozoic sediment rock in Ethiopia outcrop in three different area Mekelle basin, Abay Basin and Ogaden basin. In Mekelle basin the Mesozoic carbonate unit studied in different aspects. The detail facies and paleontological of studies have been conducted in sheket section. This study main aim is to detail investigation of micro and macro paleontology of calcareous unit in the Sheket section by investigates field observation and Petrographic analysis. By using that method micro and macro fossil, the age and the paleoenvironmental was able to determine. Based on the field observation by describe the thickness, texture and color different units were recognize: bedded and Micritic Limestone mostly interbedded with Marl, calcareous shale and Fossiliferous limestone, Marl which gray color and found interbedded with mostly with micritic and fossiliferous limestone but also with calcareous shale, fossiliferous limestone have brown color and have macro sized of bivalve fossil and calcareous shale have laminated and Fissility nature mostly found intercalated with marls. In addition to field investigation twenty thin sections were examined by using Petrographic microscope. Based on both Petrographic analysis and field investigation ten Microfacies type have been recognizing: Bioclastic packstones/Floatstone, Foraminifera Bioclastic/ packstone, Oobiosparite/grainstones, Oopelbiomicritic/wackestone, Bioclastic packstone, Crinoid grainstones, Bioclastic Mudstone, Bioclastic wackestone, Bioclast spiculite /packstone and Peloidal-Bioclastic /wackestone. And also four adjacent depositional environments were interrelated based on micro facies analysis, facies association and lithology those are open marine shelf, slope, plate form margin and deep basin. The overall depositional environment is from shallow to deep marine environment. The diagenetic process that affected the Antalo limestone during the studies includes fracture, cementation, dissolution, micritization neomorphism and silicification. There are different types of micro and macro fossil in the study area based on paleontological studies like coral, gastropoda, bivalve, ostracode, Echinodermata, cephalopoda and foraminifera are recognized. The age of carbonate unit of sheket section indicates as: from Bathonian to Callovian due to the presence of index fossils of pfenderella Arabica, Pfenderina neoucomiensis. Due to the presence of Genus praechrysalidina there is possibility this carbonate unit may be extended to Tithonian. The sheket sections of carbonate unit were correlated with intra regional section of mekelle basin.
Description
Keywords
Sheket, Microfacies, Micro and Macro Fossil, Facies Association and Mekelle Basin