Lower Eocene Hyperthermal and Transgressive Events as Revealed From Stable Isotopic Analysis of Lignite Bearing Coastal Deposits From Kutch Basin, Western India

Miocene instead of Jurassic: the importance of sound fieldwork for paleontological data analysis

“…Ammonite evidence.-The origin of the ammonites recorded by Mitra and Ghosh (1979) clearly is the Oxfordian Dhosa Oolite Member, which seems to contradict the statement made above. Their occurrence at the pond locality can be explained in two ways.…”

“…(1) They either are allochthonous, derived from the ridge exposing the Dhosa Oolite Member ∼1.6-2.1 km away, having been transported during flash floods to the pond area in recent times. Mitra and Ghosh (1979) did not provide any information whether the ammonites were collected from the section or from scree. (2) Alternatively, if the ammonites were collected from the section, they could have been reworked, transported, and become incorporated in younger sediments during deposition of the turritellid-dominated molluscan assemblage.…”

“…*Corresponding author. Das et al (2018) described four turritellinid species, Turritella jadavpuriensis Mitra and Ghosh, 1979, T. jhuraensis Mitra and Ghosh, 1979, T. amitava n. sp., and T. dhosaensis Das et al, 2018, and declared them as the oldest members (by 30 million years) of the family Turritellidae.…”

“…They accepted the lithostratigraphic position of the beds they investigated as part of the Dhosa Oolite Member and found a single belemnite specimen, Belemnopsis langanensis (Futterer, 1894) in their section. Based on the ammonite evidence obtained by Mitra and Ghosh (1979) as well as subsequent biostratigraphic studies on the Dhosa Oolite Member and lithological considerations, they placed the Turritellabearing horizons in the upper part of the lower Oxfordian. Saha et al (2021), in an attempt to erect a biostratigraphic scheme of the Jurassic sedimentary successions of the Kachchh and Jaisalmer basins, recognized the Turritella Zone for the upper Oxfordian strata of the Kachchh Rift Basin and correlated it with the Bifurcatus Ammonite Zone.…”

“…The documentation of a rich gastropod fauna from Oxfordian strata of the Kachchh Basin of western India, which is dominated by turritellids (Mitra and Ghosh, 1979;Das et al, 2018) and comprising more than 20 species (Saha et al, 2021), seems to underpin the point made by Wright et al (2003) and Wright (2000, 2009) that the Phanerozoic record of macrobenthic communities is generally strongly skewed. However, as we demonstrate in the following, the age of the assemblage from Kachchh has been wrongly determined: it is Miocene and not Late Jurassic.…”