RETRACTED: Facies analysis and depositional environments of the Oligocene–Miocene Asmari Formation, Zagros Basin, Iran

ABSTRACT We document and discuss the results of detailed fieldwork, facies analysis and the subsequent integration of paleoecological evidence from the Middle Eocene carbonate ramp succession in the southeast Zagros Basin (Jahrum Formation). A combination of a sea-level fall and tectonic and diapiric basement uplift favored the initiation of the Jahrum carbonate platform. The lower portions are affected by pervasive, probably early diagenetic dolomitization, whilst the upper Jahrum consists mainly of limestone. Here, the focus is on the limestone portions of the Jahrum Formation. Based on the abundance, diversity and rapid evolutionary turnover of the alveolinids and nummulitids, the limestone intervals of the Jahrum Formation are interpreted for the upper Middle Eocene (Bartonian). The Jahrum Formation is capped by a major unconformity and overlain by the Lower Oligocene mixed clastic/carbonate Razak Formation. Based on data from field sections, eight facies associations and a series of sub-types have been established, which correspond to inner-, middle-and outer-ramp depositional environments. In their overall context, these data show a southward-dipping inner-ramp-to-basin transect. Towards the Coastal Fars (e.g. Hulur-01 Well) the Jahrum grades laterally into deep-marine Pabdeh foredeep shale units. Based on facies analysis and paleoecological evidence from larger benthic foraminifera, a major transgressive-regressive pattern is recognized in all outcrop sections of the Jahrum. The lowermost stratigraphic units of the formation are here interpreted as a distally steepened ramp. Evidence comes from abundant allochthonous shallow-water facies in the distal, deeper-ramp setting. Shallow-water carbonate clasts were exported towards the basin, a feature that is probably linked to relative sea-level fall control. Furthermore, local to regional basement instabilities by salt diapir-related basement reorganization was arguably of significance. Upsection, evidence is found that the ramp system evolved from a distally steepened to a homoclinal geometry with an overall very gentle slope geometry during the Late Bartonian. The data shown here are significant for those concerned with the Paleogene evolution of the southeast Zagros Basin and provide a well-exposed case example of a Middle Eocene carbonate ramp factory.

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Biostratigraphy, paleoecology, and paleoenvironmental reconstruction of the Asmari formation in Zagros basin, southwest Iran

Arabian Journal of Geosciences ◽

10.1007/s12517-015-2152-5 ◽

2016 ◽

Vol 9 (2) ◽

Cited By ~ 6

Author(s):

Umid Kakemem ◽

Mohammad Hossein Adabi ◽

Abbas Sadeghi ◽

Mohammad Hasan Kazemzadeh

Keyword(s):

Asmari Formation ◽

Paleoenvironmental Reconstruction ◽

Zagros Basin ◽

Southwest Iran

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Late oligocene-early miocene benthic foraminifera and biostratigraphy of the Asmari Formation south Yasuj, north-central Zagros basin, Iran

Carbonates and Evaporites ◽

10.1007/bf03176247 ◽

2008 ◽

Vol 23 (1) ◽

pp. 1-10 ◽

Cited By ~ 10

Author(s):

Sara Hakimzadeh ◽

Ali Seyrafian

Keyword(s):

Benthic Foraminifera ◽

Early Miocene ◽

Asmari Formation ◽

Late Oligocene ◽

Zagros Basin ◽

North Central

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Facies Analysis and Depositoinal Environment of D-3 Reservoir Sands Vin Field, Eastern Niger Delta

Journal of Geography Environment and Earth Science International ◽

10.9734/jgeesi/2019/v19i230080 ◽

2019 ◽

pp. 1-19

Author(s):

Onyewuchi, Chinedu Vin ◽

Minapuye, I. Odigi

Keyword(s):

Seismic Data ◽

Niger Delta ◽

Depositional Environment ◽

Gamma Ray ◽

Facies Analysis ◽

Depositional Environments ◽

Width Ratio ◽

Neutron Density ◽

Wireline Logs ◽

Isopach Map

Facies analysis and depositional environment identification of the Vin field was evaluated through the integration and comparison of results from wireline logs, core analysis, seismic data, ditch cutting samples and petrophysical parameters. Well log suites from 22 wells comprising gamma ray, resistivity, neutron, density, seismic data, and ditch cutting samples were obtained and analyzed. Prediction of depositional environment was made through the usage of wireline log shapes of facies combined with result from cores and ditch cuttings sample description. The aims of this study were to identify the facies and depositional environments of the D-3 reservoir sand in the Vin field. Two sets of correlations were made on the E-W trend to validate the reservoir top and base while the isopach map was used to establish the reservoir continuity. Facies analysis was carried out to identify the various depositional environments. The result showed that the reservoir is an elongate , four way dip closed roll over anticline associated with an E-W trending growth fault and contains two structural high separated by a saddle. The offshore bar unit is an elongate sand body with length: width ratio of >3:1 and is aligned parallel to the coast-line. Analysis of the gamma ray logs indicated that four log facies were recognized in all the wells used for the study. These include: Funnel-shaped (coarsening upward sequences), bell-shaped or fining upward sequences, the bow shape and irregular shape. Based on these categories of facies, the depositional environments were interpreted as deltaic distributaries, regressive barrier bars, reworked offshore bars and shallow marine. Analysis of the wireline logs and their core/ditch cuttings description has led to the conclusion that the reservoir sandstones of the Agbada Formation in the Vin field of the eastern Niger Delta is predominantly marine deltaic sequence, strongly influenced by clastic output from the Niger Delta. Deposition occurred in a variety of littoral and neritic environment ranging from barrier sand complex to fully marine outer shelf mudstones.

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