Stratigraphical study of the Late Jurassic Early Cretaceous boundary of the Southern part of the Coastal Chain, Syria

Abstract

The Upper Jurassic deposits is represented by Al-Nasreh Formation and the Lower Cretaceous deposits is represented by Bab-Janeh Formation. The aim of the present research is to study the boundary between Late Jurassic Early Cretaceous in the Southern part of the Coastal Chain of Syria. To achievement this study it had been selected four surface sections and it is from North to South (Gnien- Mashta Al helo- Kafron-Al Nasreh).

Al Nasreh Formation consists of limestone sediments and dolomitic limestone with marl beds. While Bab Janeh Formation consists of dolomitic marl, limestone and marly limestone. The thickness of Al Nasrh and Bab Jinh formations decrease from south to north (Al Nasreh-Mashta Al helo- Kfron-Gnien).

Based on the micropaleontologic study which is depended mainly on the Benthic Foraminifera it had been subdivided the Late Jurassic to two biozones which are from the bottom to the top:

Kurnubia palastiniensis Biozone

Alveosepta jaccardi Biozone

and one biozone in the Early Cretaceous:

Palorbitolina lenticularis Biozone

The present study confirms existence of the stratigraphic hiatus which extent 25.8 m.y included the top of the Late Jurassic (Bortlandian) and the base of the Early Cretaceous (Berriasian- Valanginian- Hauterivian-Barremian). The reason of the stratigraphic hiatus in our opinion it may cause to the regression of the sea on the area during the 25.8 m.y, and while the strata of the mentioned ages consonant superficially, so the reason of the stratigraphic hiatus indicated to the non-deposition and in the consequence there isn't any erosion which it should existence angular disconformity.