ABSTRACT

The first study of early cretaceous succession in Northeast of Torbat-e-Heydarieh, led to recognition of 30 genera and 25 species of benthic foraminifera such as Rectodictyorbitolina sp., Dictyoconus arabicus, Orbitolina discoidea, Palorbitolina lenticularis, Mesorbitolina parva, Orbitolina kurdica, Praeorbitolina sp., Valvullammina picardi, Pseudocyclamina lituus, Charentia cuvillieri, Lenticulina sp., Nezzazata picardi, Quinqueloculina robusta, Nautiloculina oolitica, Subaudia minuta, Praechrysalidina infracteracea, Rumanoloculina sp., Choffahella decipiens, Vercorsella arenata. Regard to Stratigraphy range of above mentioned, the Barremian–Aptian age suggested for this succession.

Keywords:Torbat-e-Heydarieh, Cretaceous, Benthic Foraminifera

1. Introduction

Stratigraphic cuts located in Razavi Khorasan, 5 km from NE Torbat Heydarieh, in the Esfiyukh section region have been studied; and the geographical characteristics of this cut with the longitude 5915 and the latitude of 35 20; 60 thin sections are studied [1] .

2. Discussion

Sediments thickness in this cut is about 175 m, and consists of Alternatives lime including medium thick layer to very thick layer. This section with a few meters of conglomerates is held on the Jurassic or older sediments and contains red dark red sand stone to brown sand stone with angular conformity; this section is also covered in the same format with the cretaceous sediments or younger ones.

Target sequence from bottom to top are:

1) Massive gray limestone containing microfossil orbitolina (5/21 m).

2) Brown) gray fossiliferous limestone containing abundant rudist (5/1 meter).

3) Massive gray limestone containing microfossil orbitolina (71 meters).

4) Dolomite (5/0 mm).

5) Thick limestone layer containing a light gray and brown algae and calcareous microfossil orbitolina (80 meters).

Microscopic study of thin sections led to the identification of 30 genera and 25 species of fossil benthic foraminifera as below:

Choffatella decipiens, Vercorsella arenata, Cuneolina camposaurii, Pseudocyclamina hedbergi, Cuneolina pavonia, Maynsina sp., Debarina hahounerensis, Pseudocyclamina lituus, Charentia cuvillieri, Lenticulina sp., Nezzazata picardi, Quinqueloculina robusta, Nautiloculina oolitica, Subaudia minuta, Praechrysalidina infracteracea, Rumanoloculina sp. Valvullammina picardi, Orbitolina conoidea, Rectodictyorbitolina sp., Dictyoconus arabicus, Orbitolina discoidea, Palorbitolina lenticularis, Mesorbitolina lotzei, Orbitolina kurdica, Praeorbitolina sp., Chrysalidina gradata, Everticyclammina hedbergi, Mesorbitolina parva, Praeorbitolina cormeyi, Dictyoconus pachymarginalis [2] -[6] .

The age of foraminifera Barremian-Aptian is proposed for the sequence which is shown in the Figure 1 and Figure 2. Some of benthic foraminifera cutting Esfiyukh Mountain are listed and shown in the Figure 3. The names of these cuttings is also referred in the below based on A, B, … X.

Figure 2. Geographical map of Esfiyukh.