Organic matter depositional microenvironment in deltaic channel deposits of Mahanadi river, Andhra Pradesh

Quantitative and qualitative variations in microscopic plant organic matter assemblages and its preservation state in deltaic channel deposits of Mahanadi River was correlated with the depositional environment in the ecosystem in order to prepare a modern analogue for use in palaeoenvironment studies. For this, palynological and palynofacies study was carried out in 57 surface sediment samples from Birupa river System, Kathjodi-Debi River system and Kuakhai River System constituting Upper, Middle and Lower Deltaic part of Mahanadi river. Theapex of the delta shows dominance of Spirogyra algae indicating high nutrient, low energy shallow ecosystem during most of the year and recharged only during monsoons. The depositional environment is anoxic to dysoxic in the central and south-eastern part of the Middle Deltaic Plain (MDP) and Lower Deltaic Plain (LDP) indicated by high percentage of nearby palynomorphs, Particulate Organic Matter (POM) and algal or fungal spores. The northern part of the delta show high POM preservation only in the estuarine area in LDP but high Amorphous Organic Matter (MOA) in MDP. The sediment here is deposited under dysoxic to oxic fluvial conditions. Thus, the monsoon intensity, direction of fluvial discharge, and the landward extent of sea water incursion through river mouths inducing bottom water salinity play an important role in defining the magnitude of POM and its preservation in the shallow Mahanadi deltaic ecosystem

A record on benthic foraminiferal abundance and distribution in Gosthani estuary, Bheemunipatnam, Andhra Pradesh.

425-429A total of 482 Benthic foraminifera belonging to 23 species have been identified in the sediment samples of Gosthani estuary. The Ammonia beccarii, Anomalina sp., Asterorotalia dentata, Ammonia tepida, Quinquloculina seminulum, Asterorotalia trispinosa, and<i style="mso-bidi-font-style: normal"> Elphidium crispum are abundant<i style="mso-bidi-font-style: normal">. Anomalina sp., represent the shelf environment and it is a good indication of flooding or marine water incursion into the estuary. Q-mode cluster analysis revealed that the foraminifera could be grouped into 6 clusters. Occurrence and distribution of foraminiferal assemblages studied in the Gosthani estuary sediments, infers that these sediments were deposited in marine environment. </span

Distribution of benthic foraminiferal assemblages in Nagavali river estuary, Srikakulam, Andhra Pradesh

875-881Fifteen sediment samples were collected from estuarine environment of Nagavali River Estuary and 237 foraminifera belonging to 23 species have been identified in the sediment samples. Faunal diversity 23% and distribution are 42% in this estuary. Q-mode cluster analysis revealed that the foraminifera could be grouped into 4 clusters. The Ammonia tepida, Noniondepressulum, Quinqueloculinaseminulum, Ammonia beccarii, Quinqueloculinasp., Nonionsp., are abundant species. Occurrence and distribution of foraminiferal assemblages studied in the Nagavali estuary sediments, infers that these sediments were deposited from marine to brackish environment