Despite looking almost identical, the upper and lower members of the Ankareh For

Question

Despite looking almost identical, the upper and lower members of the Ankareh Formation are significantly different in age. According to some authors, the upper member is Late Triassic and the lower member is mostly Early Triassic; perhaps surprisingly, the middle member, the famous "Gartra Grit" (which is not present in all localities, at Utah the Red Butte area) is not Middle Triassic, but instead was deposited during the Late Triassic -- and it is conformably overlain by the upper member of the Ankareh Formation. What's the answer to this interesting chronostratigraphic puzzle?

Explanation / Answer

According to the recent study and research it was found that ankareh formation silicious detrital deposites which are mainy red ankareh sheales which frequently become sandy through considerable thikness of the matter. it also remarked the beds marks rether coarse whitish sandstone, which is almost 20 -55 feet thick. the saperation line between ankareh and underlying thaynes formation is generally made upon lithologic ground,and these are all the characteristics members of this ankareh formation. the age of these two layer may be different.

the late triassic is the third and final of three epoches of triassic period in the geographical timeline scale.it is one of the major mass extinct event of the earth which formed on the basis of corrsponding of the upper triassic.in europe it is called keuper and in in german it is called rock statra.the extinction event of species begun during the late triassic which resulted in the dissapearence of about 78% of all terresterial and marine live species. the age of this triassic is begun from the establishment of carnian age and it is the first stage which occur during the extinction of species.

early triassic is the first stage of the three epoches event .it formed in beween the year about 252-247 million years ago.it is also collectively known as the lower triassic of all the three layers.this series is coveal with scythian stage which is not included in the modern timescale .but it can be found in older literatues.in europe most of them are known as red beds now.

gartra grit is the sequential formation of the upper layers of triassic.when continental rocks get deposited in a back-arc basin a magmatic volcanic arc on western and southwestern margin of the triassic which provided both volcanic ash and clastic detrious to the triassic which result in depositional of the large part of colorado plataeu with the gatra grit. basically it is not a saperate leyers which be termed as middle but the fact is that it is the deposites which formed during the formation of upper layer or late triassic layer.

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