Palynodebris Analysis and Depositional Environment of Yingkiong Group of East and Upper Siang Districts, Arunachal Pradesh, India

The present study was carried out along the Yamne river section of the East and Upper Siang Districts of Arunachal Pradesh. The area presents the Eocene Yingkiong Group of sediments exposed on the road and river sections from the north of Ranaghat up to Yingkiong. The dominating rock types encountered are sandstone, limestone, shale, carbonaceous shale and streaks of coal. The palynological study reveals the scanty occurrence of palynofossils and foraminiferal linings. The palynodebris assemblage is dominated by charcoal and degraded black debris along with considerable amount of amorphous organic matter and well preserved woody structures. Presence of charcoal and degraded black debris indicate oxidizing environment at the time of deposition of the sediments while amorphous organic matters with well preserved woody structures point that the study area experienced recurrence of reducing environment. From the occurrence of foraminiferal linings, the depositional environment can be envisaged to be shallow marine. The palynodebris assemblage together with coal occurrence indicates a tropical to sub-tropical climate with high humidity and heavy rainfall prevailed in the area of deposition.