The lower parts of the Oligo-Miocene Qom Formation in the Kegharaki (SE Jiroft) and Shurab (SE Qom) areas: biostratigraphy, microfacies and depositional environments

نوع مقاله : مقاله پژوهشی انگلیسی

نویسندگان

1 کرمان، دانشگاه تحصیلات تکمیلی صنعتی و فناوری پیشرفته، پژوهشگاه علوم و تکنولوژی پیشرفته و علوم محیطی، گروه اکولوژی؛

2 عضو هیأت علمی گروه زمین شناسی دانشگاه پیام نور، تهران، ایران

چکیده

In order to determine the transgression time of the Tethyan Seaway in Jiroft and Qom areas, and to analysis depositional conditions at the same time, the basal parts of two exposed sections (Kegharaki and Shurab) were studied in term of the biostratigraphy, microfacies and depositional environments. In the Kegharaki section Larger benthic foraminifera are mainly represented by nummulitids, lepidocyclinids, and Amphistegina. In the Shurab section foraminifera are mainly represented by miliolids, Operculina, Amphistegina, and textularids. The presence of Nummulites fichteli/intermedius, Nummulites vascus and lepidocyclinids in the lower parts of the Kegharaki section indicates that the basal deposits could be attributed to the late Rupelian. The basal part of the Shurab section is indicative of the late Rupelian?- Chattian. Besides, the presence of tuffaceous layers in the study sections is indicative of contemporaneous volcanic activity.

Ten microfacies were identified in the basal parts of the study sections. Microfacies associations of the Kegharaki section cover an area from open marine towards open lagoon environments. Coral patch reefs are present, but there is no reef complex with sigmoidal geometries. Microfacies cover an area from restricted lagoons towards open marine environments in the Shurab section. Most parts of the Kegharaki section with an association of large and flat perforate foraminifera were deposited in normal saline waters in open marine environments (in the middle ramp). The Shurab section was deposited mainly in the restricted lagoons to open marine environments. The abundance of larger benthic foraminiferal and coralline red-algae and coral facies indicates a tropical–subtropical palaeoenvironment.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

The lower parts of the Oligo-Miocene Qom Formation in the Kegharaki (SE Jiroft) and Shurab (SE Qom) areas: biostratigraphy, microfacies and depositional environments

نویسندگان [English]

  • Ebrahim Mohammadi 1
  • Reza Sadeghi 2
1 Department of Ecology, Institute of science, High technology and environmental science, Graduate University of advanced Technology, Kerman
2 Department of Geology, Payame Noor University (PNU), P. O. Box 19395-3697, Tehran, Iran
چکیده [English]

In order to determine the transgression time of the Tethyan Seaway in Jiroft and Qom areas, and to analysis depositional conditions at the same time, the basal parts of two exposed sections (Kegharaki and Shurab) were studied in term of the biostratigraphy, microfacies and depositional environments. In the Kegharaki section Larger benthic foraminifera are mainly represented by nummulitids, lepidocyclinids, and Amphistegina. In the Shurab section foraminifera are mainly represented by miliolids, Operculina, Amphistegina, and textularids. The presence of Nummulites fichteli/intermedius, Nummulites vascus and lepidocyclinids in the lower parts of the Kegharaki section indicates that the basal deposits could be attributed to the late Rupelian. The basal part of the Shurab section is indicative of the late Rupelian?- Chattian. Besides, the presence of tuffaceous layers in the study sections is indicative of contemporaneous volcanic activity.

Ten microfacies were identified in the basal parts of the study sections. Microfacies associations of the Kegharaki section cover an area from open marine towards open lagoon environments. Coral patch reefs are present, but there is no reef complex with sigmoidal geometries. Microfacies cover an area from restricted lagoons towards open marine environments in the Shurab section. Most parts of the Kegharaki section with an association of large and flat perforate foraminifera were deposited in normal saline waters in open marine environments (in the middle ramp). The Shurab section was deposited mainly in the restricted lagoons to open marine environments. The abundance of larger benthic foraminiferal and coralline red-algae and coral facies indicates a tropical–subtropical palaeoenvironment.

کلیدواژه‌ها [English]

  • Oligo-Miocene
  • Larger benthic foraminifera
  • Biozonation
  • Tethyan Seaway
  • Iran
پژوهش های چینه نگاری و رسوب شناسی

مقالات آماده انتشار، پذیرفته شده
انتشار آنلاین از تاریخ 24 شهریور 1403

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