Microfacial Study, Fossil Assemblages and Depositional Environment of Wadi As Sir Limestone Formation, Jordan

Mona Al-Hawamdeh,Habes Mohammad Al-Mashakbeh

doi:10.4236/ojg.2020.105026

Abstract

This paper studies the microfacies, fossil contents, and the depositional environment of Wadi As Sir Limestone Formation exposed in the Al-tayyar area Zarqa Governorate, Northeastern Jordan. A total number of 35 samples were collected from a 30 m thick quarry section and used to prepare 35 thin sections. Some samples were washed over a 63 μm sieve, oven-dried at 50°C, sieved, and picked for benthic foraminifera analysis. Microscope analysis used to describe the microfacies and fossil contents. Four microfacies types and four lithological units are distinguished and described from the bottom to the top; the chalky unit (Unit-1) composed of bioclastic wackestone and biomicrite microfacies, and the dolomitic unit (Unit-2) immediately is existed above unit 1 composed dominantly of bioclastic mudstone and biomicrite microfacies. Marly limestone (Unit-3) is the following upwardly unit composed of bioclastic packestone and biosparite Microfacies, and the uppermost unit is limestone (Unit-4) consisted of bioclastic grainstone and biosparite microfacies. The fossil contents that were recognized in the studied thin sections and samples; bivalves, gastropods, pelecypods, cephalopods echinoderms, radiolarian, stromatoporoids, bone fragments, Saccaminopsis sp., Cibicidoides sp., Cibicides sp., Cyclammina sp., calcareous algae (Koninckopora and gymnocodiaceans), worm tubes, serpulids, and plentiful ostracods. The current study indicates that the Wadi As Sir Limestone Formation has deposited in a restricted circulation shallow shelf with low energy conditions most probably lagoonal environment.

Highlights

In Mesozoic times Jordan was standing at the southern margin of the Tethys Ocean
This paper studies the microfacies, fossil contents, and the depositional environment of Wadi As Sir Limestone Formation exposed in the Al-tayyar area Zarqa Governorate, Northeastern Jordan
The fossil contents that were recognized in the studied thin sections and samples; bivalves, gastropods, pelecypods, cephalopods echinoderms, radiolarian, stromatoporoids, bone fragments, Saccaminopsis sp., Cibicidoides sp., Cibicides sp., Cyclammina sp., calcareous algae (Koninckopora and gymnocodiaceans), worm tubes, serpulids, and plentiful ostracods

Summary

Introduction

In Mesozoic times Jordan was standing at the southern margin of the Tethys Ocean. During the late Albian to Turonian times, the study area was part of a broad shallow carbonate platform situated on the passive margin of the Arabian Plate [1]. The late Cenomanian paleo-coastline ranged from southeast Jordan to present-day northwest Saudi Arabia [2]. The Late Cretaceous, Ajlun Group is probably Cenomanian to Turonian in age [1] consists of five formations from base to top composed of; Na’ur, Fuheis, Hummar, Shueib, and Wadi As Sir Limestone Formations [3]. The group composed exclusively of carbonate rocks except in the extreme southern part of the country where detrital rocks make up a great part of the sequence

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