|mhorn||Дата: Monday, 11.08.2014, 08:35 | Сообщение # 1|
|Jain S., Garg R. (2014) Jurassic benthic foraminiferal biostratigraphy – an age-constrained template for local, regional and global correlation // Journal of the Palaeontological Society of India. Vol.59. no.1. P. 1-14. |
This contribution presents the first and the largest ammonite age-constrained benthic foraminiferal dataset from the Indian Jurassics. This dataset from Jaisalmer (Rajasthan, western India) is based on a study of 77 samples yielding 149 species (22 superfamilies, 33 families and 58 genera) spanning the Bajocian to Early Tithonain interval. Due to its high resolution and large time span covered, this dataset is also ideal to document the biostratigraphic relevance, if any, of benthic foraminifers that so far have only been documented from short time intervals. Here, 18 species are common with the British Jurassic, the most with any dataset, and marginally above (19) with the adjoining Kachchh Basin; surprisingly, only 7 are common between the latter and the British Jurassic. Although the benthic foraminifers are well known to be long ranging, but, the commonness of some species with the British Jurassics suggest their biostratigraphic usefulness. These include Brizalina liassica, Ammobaculites agglutinans, Ammobaculites coprolithiformis, Citharina colliezi, Citharina flabellata, Dentalina gumbeli, Epistomina rugularis, Falsopalmulina deslongchampsi, Frondicularia franconia, Lenticulina münsteri, Lenticulina quenstedti, Lenticulina subalata, Nodosaria hortensis, Opthalmidium carinatum, Pseudonodosaria vulgate, Reinholdella crebra, Vaginulina barnardia and Verneulinoides tryphera. Additionally, because of higher ammonite dating capability of the present study, the foraminiferal species are grouped into Stage based stratigraphic categories of Restricted, First and Last Occurrences. This categorization will enable a ready and robust age-limited template of benthic foraminiferal dataset for future local, regional and global correlation.
Middle Jurassic - Lower Cretaceous ammonites & aptychi