This paper investigates the biostratigraphy of the Palaeocene-Lower Eocene sequences in the Bibi Hakimeh 2 subsurface/subterranean sections located in the Bibi Hakimeh Oil Field. The Palaeocene-Lower Eocene sequences are induced as part of the Pabdeh Formation. They are 49 m in thickness and are made up of clayey limestone with chert intercalations. Biostratigraphic investigations identified 10 genera and 51 species of Planktonic Foraminifera which with respect to the specific planktonic species and according to the newest Wade Biozonation led to the determination of 9 biozones and 4 subzones. The Palaeocene-Early Eocene biostratigraphic boundary determined previously in accordance with the Wynd Biozonation was reviewed with respect to the new biozonation. Moreover, the impression of the PETM on the Planktonic Foraminifera found in the Bibi Hakimeh subsurface section, has been occurred at P/E boundary on global scale was studied. Based on this research we can conclude the P/E biostratigraphic boundary border is occurred ranges between 2125 - 2124 meters in Pabdeh formation.
The Zagros Orogenic Belt is located in the middle section of the Himalayan Alps Mountain range [
A host of studies have been carried out on the Cenozoic era and specifically on the Palaeogene period. Wynd [
Biostratigraphic characteristics of the Bibi Hakimeh 2 subsurface/subterranean sections located in the Bibi Hakimeh Oil Field have been investigated in this paper. Bibi Hakimeh Oil Field is situated in the Kohkiloyeh & Boierahmad Province, in the central region of the city of Gachesaran. 70 km in length and 5 km in width, the field is located in the southwestern region of Iran, 210 km southeast of Ahwaz on the southern region of the Gachesaran Oil Filed (
- Study of the Palaeocene and Eocene lithostratigraphic deposits (Pabdeh For- mation).
- Study of the biostratigraphy and identification of the specific microfossils and determination of new biozonations in by the aid of the microfossils.
- Comparison of new biozonations with extensive older biozonations and transformation of the Palaeocene-Eocene boundary on this basis.
The research is divided into two sections:
Laboratorial and Library-Based
In the laboratorial part, 150 microscopic thin-sections prepared by the Oil Company, were studied using PLM, Polarised Light Microscope. The cross-sec- tions were examined from a fossil content viewpoint and the biozonation of the Bibi Hakimeh subsurface/subterranean section was determined through the identification of the specific microfossils, their appearance/shape, emergence and decline period. Various sources such as Postuma [
Investigation of the peaks of the gamma and sonic waves alongside inspection of the cuttings produced within drilling operation indicates that the depositional sequence in this well consists of the Fars group of deposits, Asmari Formation limestones, marl and limey clay replete with cherts of Pabdeh Formation, clayey limestones replete with chert, and Gurpi Formation marl, and Bangestan sequence group in a top-down direction. This sequence is 1310 m in thickness. Palaeocene and lower Eocene deposits, and clayey limestones including chert interlayers are indicative of the Paabdeh Formation. This formation has a thickness of 298 m in this well. The upper boundary of this formation is contiguous with the Oligocene-aged Asmari Formation while its lower boundary is contiguous with the Paabdeh Formation. The Palaeocene and lower Eocene deposits of the Paabdeh Formation in the Bibi Hakimeh-2 well have a thickness of 49 m and in a top- down direction including:
49 m of clayey limestone alongside chert interlayers (
Study of the Palaeocene and Lower Eocene depositional microfossils in the Bibi Hakimeh subsurface/subterranean section, revealed 10 genera and 51 species of Planktonic Foraminifera, 9 genera and species of benthic foraminifera, and 1 non-foraminifera form. The latest Wade Biozonation was employed in this research and was compared with the older Wynd [
Wade [
Zone P4. Globanomalinapseudomenardii Taxon-Range Zone
This biozone has been determined according to the domain of the Globanomalinapseudomenardii species [
P4b. Acarinina subsphaerica Subzone (partial-range-subzone)
This subzone is of the partial-range type and covers the distance/interval between the highest occurrence, Parasubbotinavariospira (HO) and the lowest occurrence of Acarininasoldadoensis (LO) [
Acarinina sp., Acarinina nitida, Morozovellaapanthesma, Acarinina subsphaerica, Subbotina triangularis, Igorinatadjikistanensis, Igorina pusilla, Morozovella velascoensis, Igorinaalbeari, Morozovellaacutispira, Morozovellaconicotruncata, Morozovella angulate, Globanomalinapseudomenardii, Subbotina velascoensis, Morozovella acuta.
P4c. Acarinina soldadoensis Globanomalinapseudomenardii Subzone (concurrent-range-subzone)
This subzone is of the concurrent-range zone type and covers the interval between the lowest occurrence, of Acarininasoldadoensis (LO) and the highest occurrence of Globanomalinapseudomenardii (HO) [
Globanomalinapseudomenardii, Acarinina soldadoensis, Morozovella aequa, Acarininaesnaensis, Acarininacoalingensis, Acarinina decepta, Subbotina velascoensis, Morozovella acuta, Acarinina sp., Acarinina nitida, Morozovella velascoensis, Igorinaalbeari.
Zone P5. Morozovella velascoensis Partial-Range Zone (partial-range- zone)
This subzone is of the partial-range zone type and covers the distance between the the highest occurrence of Globanomalinapseudomenardii (HO) and lowest occurrence, of Acarininasibaiyaensis (LO) [
Zone E1. Acarininasibaiyaensis Lowest-Occurrence Zone (lowest-occur- rence-zone)
This subzone is of the lowest-occurrence zone type and covers the interval be- tween the lowest occurrence of Acarininasibaiyaensis (LO) and the highest occurrence of Pseudohastigerinawilcoxensis (LO) [
The boundary between the E1 & P5 biozones in the Bibi Hakimeh section is indistinguishable. Therefore, the age of the span between the lower boundary of the P5 biozone at 2125 m and the upper boundary of the E1 biozone at a depth of 2124 m is determined to be Late-Paleocene to Early Eocene (Latest Thanetian- Sparnacian).
Zone E2. Pseudohastigerinawilcoxensis/Morozovella velascoensis Concurrent-Range Zone
This subzone is of the concurrent-range zone type and covers the interval between the lowest occurrence of Pseudohastigerinawilcoxensis (LO) and the highest occurrence of Morozovella velascoensis (HO) [
In the Bibi Hakimeh section, the lower boundary of this biozone was determined as the lowest occurrence of Pseudohastigerinawilcoxensis at a depth of 2124 m while the upper boundary was established to be the highest occurrence of Morozovella velascoensis at a depth of 2115 m. The age of this zone is determinedas early Eocene (Sparnacian) according to the biozone defined by Wade, comparison and conformation with the same subzone and its fossil complex. The fossil complex concomitant with this zone includes (
Acarininasoldadoensis, Morozovella aequa, Acarininaesnaensis, Acarininacollectea, Acarinina decepta, Subbotina velascoensis, Morozovella acuta, Acarinina intermedia, Acarininaaquensis, Morozovella velascoensis, Igorinaconvexa, Subbotinainaquispira, Morozovella gracilis, Pseudohastigerinawilcoxensis.
Zone E3. Morozovella velascoensis Partial-Range Zone
This subzone is of the partial-range zone type and covers the interval between the highest occurrence of Morozovella velascoensis (HO) and the lowest occurrence of Morozovella formosa (LO) [
In the Bibi Hakimeh section, the lower boundary of this biozone was determined as the highest occurrence of Morozovella velascoensis at a depth of 2115 m while the upper boundary was established to be the highest occurrence of Morozovella formosa at a depth of 2113 m. The age of this zone is determined as early Eocene (Ypresian) according to the biozone defined by Wade, comparison and conformation with the same subzone and its fossil complex. The fossil complex
concomitant with this zone include:
Acarininaaquiensis, Igorinaconvexa, Morozovella gracilis, Morozovella subbotinae, Acarininacoalingensis, Morozovella aequa.
Zone E4. Morozovella formosa Lowest-Occurrence Zone
This zone is of the lowest-occurrence type and covers the distance between the lowest occurrence of Morozovella formosa (LO) and the highest occurrence of Morozovella aragonensis (HO) [
In the Bibi-Hakimeh section, the lower boundary of this biozone was determined as the lowest occurrence of Morozovella formosa at a depth of 2113 m while the upper boundary was established to be the highest occurrence of Morozovella aragonensis at a depth of 2101 m. The age of this zone is determined as early Eocene (Ypresian) according to the biozone defined by Wade and comparison and conformation with the same subzone and its fossil complex. The fossil complex concomitant with this zone include:
Acarinina primitiva, Morozovellalensiformis, Acarinina pseudotopilensis, Acarinina decepta, Acarininaesnaensis, Morozovella aequa, Morozovella subbotinae, Subbotinainaquispira, Pseudohastigerinawilcoxensis, Morozovella gracilis.
Zone E5. Morozovella aragonensis/Morozovella subbotinae Concurrent- Range Zone
This zone is of the lowest-occurrence zone type and covers the interval between the lowest occurrence of Morozovella aragonensis (LO) and the highest occurrence of Morozovella subbotinae (HO) [
In the Bibi Hakimeh section, the lower boundary of this biozone was determined as the lowest occurrence of Morozovella aragonensisa at a depth of 2101 m while the upper boundary was established to be the highest occurrence of Morozovella subbotinae at a depth of 2093 m. The age of this zone is determined as early Eocene (Ypresian) according to the biozone defined by Wade, comparison and conformation with the same subzone and its fossil complex. The fossil complex concomitant with this zone includes:
Acarinina primitiva, Pseudohastigerinawilcoxensis, Acarinina pseudotopilensis, Morozovella caucasica, Dentoglobigerinayeguaensis, Acarinina pentacamerata, Morozovella crassata, Morozovella aragonensis, Acarininaaquiensis, Acarininacoalingensis, Globigerinathekasp, Acarininabullbrooki, Acarininagraveli, Acarinina decepta, Acarininaesnaensis, Subbotinainaquispira, Igorinaconvexa.
Zone E6. Acarinina pentacamerata Partial-Range Zone
This subzone is of the partial-range zone type and covers the interval between the highest occurrence of Morozovella subbotinae (HO) and lowest occurrence of Acarininacuneicamerata (HO) [
In the Bibi Hakimeh section, the lower boundary of this biozone was determined by the highest occurrence of the Morozovella subbotinae at a depth of 2093 m. The upper boundary cannot be established due to the non-recognition of Acarininacunicamerata.
Zone E7. Acarininacuneicamerata Lowest-Occurrence Zone
This biozone is of the lowest-occurrence zone type and covers the interval between the lowest occurrence of Acarininacuneicamerata (LO) and the highest occurrence of Guembelirioidesnuttali (HO) [
Subzone E7a Acarininacuneicamerata Lowest-Occurrence Zone
This zone is of the lowest-occurrence zone type and covers the interval between the lowest occurrence of Acarininacuneicamerata (LO) and the lowest occurrence of Turborotalia frontosa (LO) [
The lower boundary of this biozone cannot be determined in the Bibi Hakimeh section due to the non-recognition of the Acarininacuneicamerata species while the upper boundary was determined by the lowest occurrence of the Turborotalia frontosa at a depth of 2086 m. The boundary between the E6 & E7a cannot be established on this basis; therefore, the same biozones were determined for the depths of 2093 to 2086 m. The age of this zone is determined as early Eocene (Ypresian) according to the biozone defined by Wade, comparison and conformation with the same subzone and its fossil complex.
The fossil complex concomitant with this zone includes:
Acarininacoalingensis, Acarininacollectea, Acarinina intermedia, Acarinina interposita, Acarinina pentacamerata, Dentoglobigerinayeguaensis.
Subzone E7b. Turborotalia frontosa Lowest-Occurrence Zone
This zone is of the lowest-occurrence zone type and covers the interval between the lowest occurrence of Turborotalia frontosa (LO) and the lowest occurrence of Guembelitrioidesnuttalli (LO) [
Acarininacoalingensis, Acarininacollectea, Acarinina intermedia, Acarininaprimitiva, Acarinina interposita, Acarininabullbrooki, Acarinina pentacamerata, Dentoglobigerinayeguaensis, Turborotalia frontosa, Chilloguembelina sp., based on Planktonic Foraminifera while 2 biozones were classified according to Wynd [
Morozevella velascoensis-Globanomalina pseudo menardii Zone (assemblages-zone)
This biozone defined by Wynd [
Morozevella subbotinae-Morozovella Formosa Morozovella aragonensis Zone
This zone referred to as zone Number 45 [
Comparison and conformation of the Wade [
Comparing superimposition at the Wade [
The PETM is also applied to separate the P/E boundary cum the phenomenon at emergence, eptinction at index foraminifera [
In the light of studies conducted by Pardo [
at tolering the heat, all the sudden the variety number of Planktonic Foraminifera at the subsurface section at Bibi Hakimeh drops down at 2125 - 2124 meters interval. The cold-water groups suite assemblages Subbotinatrangularis, Subbotinavelascoensis, Chilogumbelina sp. species have had presence from the base of the formation up to the contiguity at the boundary, and however they have disappered all the sudden at 2125 meter from Formation, reappearing at 2124 meter all the base of the formation. Warm-water foraminifera have been identified that belong to Morozovellaacuta, Acarininasoldadoensis, Acarinina nitida are among them. Pardo [
Analysis of the Palaeocene-Lower Eocene sequences of the Paabdeh Formation in the Bibi Hakimeh subsurface/subterranean section resulted in the identification of 10 genera and 51 spices of Planktonic Foraminifera. According to the latest Wade Biozonation and their appearance, emergence and decline of the Planktonic Foraminifera index, 9 biozones and 4 biosubzones were identified which were compared with the oldest biozonation performed on the Paabdeh Formation. On this basis, the Palaeocene-Lower Eocene biostratigraphic boundary, which according to the Wynd Biozonation had been located at the border of the biozone numbers 42 & 45 at 2115 m from the base of the formation, is now situated at the boundary between biozones P5 & E1 at an interval of 2124 to 2125 m from the formation base according to the Wade Biozonation. The new Wade Biozonation [
Moradian, F., Baghbani, D. and Allameh, M. (2017) Micro- biostratigrapy of the Paleocene-Lower Eoce- ne Sequences in the Bibi Hakimeh 2 Subsurface Section Located in the SW of Iran. Open Journal of Geology, 7, 147-161. https://doi.org/10.4236/ojg.2017.72010