Hypercalcified chaetetid sponges and its paleoecological significance of the Upper Jurassic Esfandiar platform in Deihuk area (Shotori Mountains, Tabas Block, central Iran)

This study shows that chaetetids display morphologies similar to such benthic organism as stromatoporoids, bryozoans and corals .Most of the chaetetids in the Esfandiar are tabular and bulbous forms. Chaetetid sponges occur mainly as hemispheroids up to a diameter of 60 cm, being more common towards the platform margin. Chaetetids clearly grew in shallow-water marine environments and they are usually inferred to indicate a shallow subtidal environment. Fossil chaetetids were a conspicuous component of reefal and associated environments during the late Paleozoic (late Carboniferous and Permian) and part of the Mesozoic (Middle Triassic into the Cretaceous) in the Tethys but were mainly dispersed in the Esfandiar platform. Hypercalcified sponges with a chaetetid skeleton are members of the marine sessile benthos. The skeleton of hypercalcified demosponges is a rigid a specular skeleton, or a combination of both .Growth forms of chaetetids in the Esfandiar Formation are: bulbous, domical, laminar and complex. At the base of the Esfandiar Formation, most of the chaetetids have ragged margins indicating episodic sedimentation and others that were reoriented during life show changes in growth directions.Bioclastic rudstones and bioconglomeratic layers indicate in situ reworking by storms of the platform sediments. The predominance of large chaetetids may reflect particularly strong storm events or proximity to the platform margin. At the high-energy platform margin, ooid shoals protected the platform interior from the open sea during the Middle Oxfordian to Lower Kimmeridgian,