Palaeoclimatic significance of non - striate disaccate pollen in Yellandu coalfield of Godavari graben, Telangana State

The present palaeopalynological study deals with the significance of non - striate disaccate pollen from bore hole Q - 563 of Yellandu coalfield (Jawahar Khani - 5 coal block), Kothagudem sub-basin and to determine the age and palaeoclimatic interpretations of the study area based on the pollen morphological characters. For the palynological investigation, sixty samples were thoroughly analyzed in which fairly diversified palynofloral assemblages of Gondwanic affinity were recorded. About 30 genera and 50 species of palynomorphs, belong to Glossopteridales, Coniferales, Cordaitales of gymnospermous pollen, pteridophytic spores. In the present communication, the palynoflora belongs to Glossopteridales viz. Scheuringipollentites barakarensis, S. maximus, S. tentulus, Ibisporites diplosaccus, Primuspollenites levis, P. densus and Sahnites thomasii etc. Frequency distribution pattern of the palynotaxa reveals that the assemblage is dominated by the non - striate disaccates followed by striate disaccates, monosaccates (gymnosperms) and pteridophytic spores. The diversified palynoassemblage of both non striate and striate disaccates pollen strongly signifies that the Yellandu coal belt of Godavari graben belongs to Barakar Formation of Early Permian age (Late Sakmarian – Early Artinskian). Predominance of non - striate disaccate pollen recorded from the Yellandu sediments indicates a warm and high humid climatic condition with fluvial environment of deposition.

Palaeobotanical and biomarker evidence for Early Permian (Artinskian) wildfire in the Rajmahal Basin, India

This study provides a combined analysis on the palynology, fossil charcoal and biomarkers of the subsurface coal deposits from a borehole RMB #2 drilled at the Dhulia Coal Block, Rajmahal Basin, India, in attempts to establish the chronology of sedimentation and to propose palaeobotanical as well as geochemical evidence for the occurrence of wildfires in these sediments. The palynological investigation suggests a Scheuringipollenites barakarensis palynoassemblage from the lower Barakar Formation, dated as Artinskian (Early Permian) in age. This assemblage reveals the dominance of Glossopteridales and sub-dominance of taxa belonging to Cordaitales and Coniferales. Fossil charcoal in sediments is usually recognized as a direct indicator for the occurrence of palaeo-wildfires. More data involving the anatomical features of fossil charcoal analyzed by Field Emission Scanning Electronic Microscope broaden our knowledge on Early Permian wildfires from the peninsula of India. The studied macroscopic charcoal fragments exhibit anatomical details such as homogenized cell walls, uniseriate simple and biseriate alternate pitting on tracheid walls and rays of varying heights pointing to a gymnospermous wood affinitity. The excellent preservation of charcoal fragments, shown by their large sizes and almost unabraded edges, suggests a parautochthonous origin. The embedded biomarker study performed for charcoal sediments and its characterization demonstrate the presence of n-alkanes, isoprenoids, terpenoids and aromatic compounds. A bimodal distribution pattern of n-alkanes with a Cmax at n-C25 is identified. Diterpenoids and pentacyclic terpenoids are identified, indicating the input of an early conifer vegetation and bacterial activity, respectively. The identified polyaromatic hydrocarbon (PAH) compounds, together with the charcoal fragments, clearly suggest that repeated wildfire events occurred during the deposition of these Artinskian sediments in the Rajmahal Basin.

Clay Mineral and Geochemical Proxies for Intense Climate Change in the Permian Gondwana Rock Record from Eastern India

The clay mineral assemblages and geochemical compositions of the Permian Talchir and Barakar mudstones of the Raniganj basin, India, have been used to interpret terrestrial paleoclimate. The Talchir Formation presents unequivocal evidences of the Permian global glacial climate, and the overlying Barakar Formation with braided fluvial deposits immediately follows the glacial amelioration stage to a humid warm climate. Sediments unaffected by burial diagenesis and originated from a similar source under contrasting climates are ideal for developing proxies for substantial climate shift. Illite (28.4-63.8%), illite/smectite (0-58.6%, 40-80% illite), chlorite (0-53.9%), and chlorite/smectite (5.6-29.8%) constitute the clay mineral assemblage in the Talchir Formation whereas illite (5.3-78.2%), illite/smectite (trace-34.1%, mostly 60-90% illite), and kaolinite (36.1-86.8%) dominate the clay mineral assemblage in the Barakar Formation. The Talchir mudrocks are enriched in mobile elements and depleted in alumina w.r.t. PAAS, have relatively higher K2O/Al2O3 ratios (~0.3), high ICV (1.12-1.28), and lower CIA values (52.6-65.1) compared to those of the younger Barakar mudstones. The Barakar mudstones are depleted in mobile elements w.r.t. PAAS, have relatively low ICV (0.33-0.62) and K2O/Al2O3 values (0.11-0.16), and higher CIA values (72.9-88.2). Textural, mineralogical immaturity, and rock fragments of different components of the basement seen in the Talchir sandstones show these sediments being a first-cycle sedimentary deposit. The distinctive clay mineral assemblage and major oxide composition of the Talchir mudrocks attest to a unique low intensity chemical weathering in cold arid climate. Significant presence of kaolinite as well as distinctive geochemical characters of the Barakar mudrocks marks a shift in the paleoclimate from cold arid to humid. This climatic shift is further supported by the proportion and composition of illite/smectite across the formations. The relative proportion of chlorite and kaolinite and composition of illite/smectite therefore closely corroborate the significant climate shift, and such proxies, therefore, are useful indicators of climate extremes in the geological record.