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<p>A study was conducted on the pelagic shale of the Upper Cretaceous Gurpi Formation in the Anarestan section of the Zagros Basin. The Gurpi Formation (Campanian–Maastrichtian) is well exposed in the Zagros Basin (SW Iran) and is considered a part of the southern Neotethys. The strata studied are situated between the carbonate rock of the Ilam Formation (Turonian-Santonian) at the base and the pelagic sediments of the Pabdeh Formation (Paleocene-Eocene) at the top. This section is located in the folded-thrust zone of Zagros, and specifically in the Fars zone (Coastal Fars). The focus of the study was on biostratigraphy of planktic foraminifera which led to the identification of 25 species belonging to 11 genera of upper Cretaceous (Campanian–Maastrichtian). Additionally, three species of planktons were identified in the lower part of the Pabdeh Formation as lower Paleocene index species. Six biozones are described for the Gurpi Formation. These biozones include 1) <i>Globotruncanita elevata</i> Interval zone; 2) <i>Globotruncana ventricosa</i> Partial range zone, 3) <i>Radotruncana calcarata</i> Total range zone; 4) <i>Globotruncanella havanensis</i> Partial Range Zone; 5) <i>Globotruncana aegyptiaca</i> Interval zone; and 6) <i>Contusotruncana contusa</i> Total range zone. According to the identified biozones, the age of the Gurpi Formation is assigned to the Early Campanian—early Late Maastrichtian. Upper Danian (Pabdeh Formation) planktics species consist of <i>Morzovella angulata</i>, <i>Globanomalina chapmani</i>, and <i>Globanomalina compressa</i>. The frequency of upper Cretaceous planktic confirms the mass extinction of the planktic foraminifera as they suddenly disappear at the end of the Cretaceous period. In fact, number of species richness of planktic foraminifera in the upper Cretaceous is estimated to be 16 mainly consisting of diversified keeled planktic foraminifera (Globotruncanids), with Heterhelicids limited to one species (<i>Heterohelix globulosa</i>). However, the stratigraphic distribution of Upper Cretaceous and Paleocene planktic foraminifera reveals an obvious hiatus at the K/Pg boundary.</p>

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Upper Cretaceous/Paleogene boundary in Southern Neotethys: Zagros Basin, Coastal Fars zone (SW Iran): Gurpi/Pabdeh formations biostratigraphic implications

  • 期刊论文

  • 发表日期：

    2026年5月26日

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  • Hajar Mashayekh,
  • Massih Afghah

摘要

A study was conducted on the pelagic shale of the Upper Cretaceous Gurpi Formation in the Anarestan section of the Zagros Basin. The Gurpi Formation (Campanian–Maastrichtian) is well exposed in the Zagros Basin (SW Iran) and is considered a part of the southern Neotethys. The strata studied are situated between the carbonate rock of the Ilam Formation (Turonian-Santonian) at the base and the pelagic sediments of the Pabdeh Formation (Paleocene-Eocene) at the top. This section is located in the folded-thrust zone of Zagros, and specifically in the Fars zone (Coastal Fars). The focus of the study was on biostratigraphy of planktic foraminifera which led to the identification of 25 species belonging to 11 genera of upper Cretaceous (Campanian–Maastrichtian). Additionally, three species of planktons were identified in the lower part of the Pabdeh Formation as lower Paleocene index species. Six biozones are described for the Gurpi Formation. These biozones include 1) Globotruncanita elevata Interval zone; 2) Globotruncana ventricosa Partial range zone, 3) Radotruncana calcarata Total range zone; 4) Globotruncanella havanensis Partial Range Zone; 5) Globotruncana aegyptiaca Interval zone; and 6) Contusotruncana contusa Total range zone. According to the identified biozones, the age of the Gurpi Formation is assigned to the Early Campanian—early Late Maastrichtian. Upper Danian (Pabdeh Formation) planktics species consist of Morzovella angulata, Globanomalina chapmani, and Globanomalina compressa. The frequency of upper Cretaceous planktic confirms the mass extinction of the planktic foraminifera as they suddenly disappear at the end of the Cretaceous period. In fact, number of species richness of planktic foraminifera in the upper Cretaceous is estimated to be 16 mainly consisting of diversified keeled planktic foraminifera (Globotruncanids), with Heterhelicids limited to one species (Heterohelix globulosa). However, the stratigraphic distribution of Upper Cretaceous and Paleocene planktic foraminifera reveals an obvious hiatus at the K/Pg boundary.