Deformed fossils and related structures in Jordan

Abstract EN

This study of the deformation of fossils due to tectonic activities is the first study to be carried out in Jordan.

Deformed fossils were found in a variety of locations such as Ajlun (Shtafina), Umm Dananier, Wadi Mujib and Jabal Waqf as Suwwan areas.

The different stress fields that produced folding, stylolization and reverse flexuring, are believed to have also produced the deformation of the fossils.

Folding, stylolization and reverse flexures are structures, which can unambiguously be referred to defined stress fields.

The deformation directions of the fossils are in this study correlated to the structures having unambiguous stress field producing them.

The correlation was very clear and accordingly therefore, deformed fossils can be used as very good indicators on the stress fields which produced them irrespective, whether these stress fields have left any macrostructures in the rocks which indicate at them or not.

Deformed fossils from Jabal Waqf as Suwwan area have a different history, because the stress field producing them was a different one.

It was a meteoritic impact stress field, which due to the very high velocity of around 18 Km / s caused all rock types to behave in a competent way for a very short time.

After which rock block movements of sliding, rotation and tilting took place gradually.

According to the results of the study of deformed fossils, Jordan was during its geologic history exposed to different stress Fields ; in an ESE-WNW direction which produced the Syrian Arc structure, followed by a SE-NW strong stress field and finally by a NNW-SSE another strong stress field which resulted in the formation of the Dead Sea Transform Fault and accompanying structures.

The deformation of fossils was not always of a ductile type where fossils were compressed in a certain direction and expanded in the other, but some fossils show shear along certain directions, with very prominent shear surfaces.

The study concludes that deformed fossils can be used as excellent indicators of stress fields, even if other structures indicating at them are not found.