The study of Upper Paleozoic and Mesozoic palynomorphs in three boreholes from the Deocha-Pachami area, Birbhum Coalfield, West Bengal, India, has allowed dating of the Talchir, Barakar, Dubrajpur, and Rajmahal format...The study of Upper Paleozoic and Mesozoic palynomorphs in three boreholes from the Deocha-Pachami area, Birbhum Coalfield, West Bengal, India, has allowed dating of the Talchir, Barakar, Dubrajpur, and Rajmahal formations, and revealed many hiatuses. The lowermost unit, the Talchir Formation, yielded earliest Permian palynomorphs. The Barakar Formation, which includes coal-bearing strata, was previously dated as Early Permian. However, data presented herein indicate an Early Permian to earliest Triassic age for this unit,containing actually the Karharbari, Barakar s.s., Kulti, and Ranigang formations as well as the basal part of the Panchet Formation. The overlying Dubrajpur Formation is Jurassic (Callovian to Tithonian), with an unconformity at its base. The uppermost Dubrajpur Formation is Tithonian-Berriasian. The palynomorphs from the intertrappeans within the Rajmahal Formation suggest an Early Cretaceous age. The revised ages of the Barakar and Dubrajpur formations are of major regional significance. The distribution patterns of spore-pollen may provide a broad spectrum of paleoclimate during Permian, Late Jurassic, and Early Cretaceous times, as there is no record of marine signatures in the study area.展开更多
文摘The study of Upper Paleozoic and Mesozoic palynomorphs in three boreholes from the Deocha-Pachami area, Birbhum Coalfield, West Bengal, India, has allowed dating of the Talchir, Barakar, Dubrajpur, and Rajmahal formations, and revealed many hiatuses. The lowermost unit, the Talchir Formation, yielded earliest Permian palynomorphs. The Barakar Formation, which includes coal-bearing strata, was previously dated as Early Permian. However, data presented herein indicate an Early Permian to earliest Triassic age for this unit,containing actually the Karharbari, Barakar s.s., Kulti, and Ranigang formations as well as the basal part of the Panchet Formation. The overlying Dubrajpur Formation is Jurassic (Callovian to Tithonian), with an unconformity at its base. The uppermost Dubrajpur Formation is Tithonian-Berriasian. The palynomorphs from the intertrappeans within the Rajmahal Formation suggest an Early Cretaceous age. The revised ages of the Barakar and Dubrajpur formations are of major regional significance. The distribution patterns of spore-pollen may provide a broad spectrum of paleoclimate during Permian, Late Jurassic, and Early Cretaceous times, as there is no record of marine signatures in the study area.
