Lithostratigraphy and sedimentary environment of the Precambrian Kushk Series of central Iran

Abstract

The Kushk Series is a distinctive late Ediacaran succession occurring in the Bafq and Behabad regions of central Iran that has yielded an extensive community of diverse Ediacara biota, including several Precambrian (Chuaria) and Ediacaran (Cloudina, Corumbella) index fossils.The Kushk Series reaches a thickness of up to 518 m and consists of shallow to deep subtidal deposits along a homoclinal carbonate ramp during a transgression/regression cycle. These deposits accumulated as part of an extensional rift basin complex resulting from the opening of the Proto-Paleotethys Ocean in northeastern Gondwana. Latest Ediacaran fossils occur in the deep-water calcareous marine shales, and represent a thriving community at the dawn of animal life.

Ediacaran diversity and paleoecology from central Iran

“…The Ediacaran fossil-bearing beds of the Kushk Series are exposed near lead and zinc mines of the Bafq (Kushk) and Behabad (Chahmir and Dardehoo) regions of Central Iran (Fig. 1; Vickers-Rich et al, 2017; Vaziri and Laflamme, 2018). The Kushk Series is situated between the western margin of the Lut Block and the eastern margin of the Central Iranian Yazd Block, reaching a thickness of 518 m in the Kushk area and thinning to 175 m in the Chahmir area (Fig.…”

“…The Kushk Series comprises 13 sub-units that include volcanic rhyolites, microdiorites, tuffs, sandy dolomitic limestones, dolomite, shales, and sandstones that were deposited as part of a homoclinal ramp (Fig. 1.3; Vaziri and Laflamme, 2018). Fossil beds occur in sub-unit 6 (Fig.…”

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Figure 1.( 1 ) Structural framework of Iran showing major tectonic plates and associated boundaries; ( 2 ) the location of study areas in the Bafq and Behabad regions, Central Iran; and ( 3 ) stratigraphic section of the Kushk Series in the Kushk (Bafq) and Chahmir (Behabad) areas, Central Iran, showing Ediacaran fossils from the sub-unit 6. Modified from Vaziri and Laflamme, 2018.

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“…Stratigraphic and sedimentological studies of the Kushk Series in the Kushk and Chahmir areas of Central Iran (Vaziri and Laflamme, 2018; Vaziri et al, 2019) have resulted in the discovery of over 250 fossil specimens representing a diverse latest Ediacaran assemblage of both soft-bodied and biomineralized fossil taxa (Vaziri et al, 2018). These deep-water calcareous marine shale deposits preserve: (1) a Nama-type assemblage of cloudinomorphs, Corumbella , erniettomorphs, and rangeomorphs; (2) the youngest kimberellomorphs ( Kimberella persii Vaziri, Majidifard and Laflamme, 2018); and (3) possible sponges ( Gibbavasis kushkii Vaziri, Majidifard, Laflamme, 2018).…”

Geobiology of the Ediacaran–Cambrian Transition: ISECT 2017

“…They suggest that the decomposition of specific minerals in response to decreasing pH allowed for the accumulation of Al and Si in close proximity to the tissues, which in turn formed the basis for eventual mineralization and fossilization. Vaziri and Laflamme (2018) present new sedimentological studies of the late Ediacaran of central Iran in "Lithostratigraphy and sedimentary environment of the Precambrian Kushk Series of central Iran". Their fossiliferous sections illustrate a transgressionregression cycle along a carbonate ramp in an extensional rift basin in response to the opening of the Proto-Paleotethys Ocean in northeastern Gondwana.…”