Permian–Triassic palynostratigraphy in Mailaram area, Godavari Graben, Andhra Pradesh, India

Abstract

Palynological investigations of five borecores, viz., GAM-3, GAM-6, GAM-7, GAM-8 and GAM-10 from Mailaram area have suggested the occurrence of complete Lower Gondwana succession in Mailaram area. Total nine palynozones have been identified on the basis of dominance, sub-dominance and appearance of various palynotaxa. These palynozones belong to Talchir, Upper Karharbari and Barakar (Early Permian), Raniganj (Late Permian) and Panchet (Early Triassic) palynofloras of Indian Gondwana. The oldest Palynozone-1 demonstrated in borecore GAM-6 (331.4–500 m) and borecore GAM-10 (505.66–581.55 m), is characterized by the dominance of Parasaccites and sub-dominance of Plicatipollenites belongs to Talchir Palynoflora; Palynozone-2 identified in borecore GAM-7 (667–749 m) and borecore GAM-8 (89.75 m) is characterized by the dominance of Parasaccites and sub-dominance of Scheuringipollenites which belongs to Upper Karharbari Palynoflora. Palynozone-3, identified in borecore GAM-6 (149.7–240.05 m) and borecore GAM-8 (84.95 m), is characterized by the dominance of Scheuringipollenites akin to Scheuringipollenites zone of Barakar palynoflora; Palynozone-4, recorded in borecores GAM-3 (294–437.98 m), GAM-7 (453–640.5 m) and GAM-8 (35.35 m) is characterized by the dominance of Faunipollenites and sub-dominance of Striatopodocarpites along with certain stratigraphically significant taxa, viz., Weylandites, Guttulapollenites, Corisaccites, Aurangapollenites and Osmundacidites. Palynozone-5, demarcated in borecore GAM-3 (144.86–221.3 m) and borecore GAM-10 (35.35 m), is distinguished by the dominance of striate disaccates along with at least 30% pollen assigned to Striasulcites; Palynozone-6, identified in borecore GAM-3 (35.1–73.08 m) and borecore GAM-7 (231–423 m), is characterized by the dominance of striate disaccates along with 20–30% of Densipollenites; Palynozone-7, recorded in borecore GAM-7 (206 m), is distinguished by the dominance of Crescentipollenites along with striate disaccates; Palynozone-8, identified in borecore GAM-7 (178.4 m), is characterized by the distinguished presence of taeniate pollen Guttulapollenites. Palynozones 4–8 belong to Raniganj Palynoflora. Palynozone-9, identified in borecore GAM-7 (166 m), is discriminated by the dominance of trilete spore Verrucosisporites and sub-dominance of taeniate pollen Lunatisporites which belongs to Triassic palynoflora. On the basis of palynological data Palynozone-1 (= Talchir palynoflora), Palynozone-2 and Palynozone-3 have been assigned to Early Permian age; Palynozones 4–8 (= Raniganj palynoflora) have been assigned to Late Permian age and Palynozone-9 (= Triassic palynoflora) has been assigned to Early Triassic age. With the aim of correlating the Permian and Triassic sediments of Mailaram area palynological investigations of five borecores were carried out.