|mhorn||Дата: Friday, 27.02.2015, 10:18 | Сообщение # 1|
|Jain S., Desai B. (2014) Biostratigraphic implications of the discovery of Late Bathonian Indonesian ammonite Macrocephalites Cf. Mantataranus Boehm [M]From the core of Jara Dome, Kachchh, Western India // Journal of the Palaeontological Society of India. Vol.59. no.2. P.1-11. |
The age of the basal sediments at Jara (Kachchh, Western India) has been a matter of debate due to the absence of time diagnostic fossils (notably of ammonites and nannofossils). Previous nannofossil records from these basal beds indicate an Early Callovian age, whereas ammonite records (largely noted in passing), point to either a Latest Bathonian or an Earliest Callovian interval. Now, for the first time, from the core (basal marl and marlstone intercalations) of the Jara Dome, discovery of a typical Latest Bathonian Indonesian ammonite Macrocephalites cf. mantataranus Boehm [M]is recorded. A similar find is now also documented from coeval Latest Bathonian strata (the Sponge beds) of the Jumara Dome, ~12 km east of Jara. Previous nannofossil assemblage data from Jara is also critically reviewed with updated biochronology and it suggests that the nannofossils assemblage is not exclusively Early Callovian age, as has been suggested but is of late Early Callovian age (upper part of the Lower Callovian Tethyan Gracilis Zone). Additionally, based on morphological similarity, coeval stratigraphic distribution and statistical analyses, the present study reaffirms the close affinity of the Indonesian M. mantataranus Boehm [M]with the Kachchh Bathonian zonal index Macrocephalites triangularis Spath [M].
thanks to Sreepat Jain for this pdf!
Middle Jurassic - Lower Cretaceous ammonites & aptychi