Middle and Late Jurassic Radiolarians from Nadanhada Terrane of Eastern Heilongjiang Province, Northeastern China

Abstract

The Nadanhada terrane of northeastern Heilongjiang, northeastern China is composed of Jurassic accretionary complexes (i.e., the Yuejinshan Complex in the west, the Raohe Complex in the east) and succedent cover beds. In this paper we report two radiolarian assemblages recognized from four black claystone samples collected from the Dalingqiao Formation in the Dajiashan area of the Raohe Complex. The Striatojaponocapsa synconexa-“Tricolocapsa” tetragona assemblage of one sample consists of eleven species in eight genera, which indicates a middle Bathonian (Middle Jurassic) age, i.e., correlative with the uppermost Striatojaponocapsa plicarum Zone to the lower Striatojaponocapsa conexa Zone. The other three samples contain 34 species in 25 genera, which indicate a late Oxfordian–early Tithonian (Late Jurassic) age. The discovery of the Late Jurassic radiolarian assemblage indicates that the Raohe Accretionary Complex was formed during the Late Jurassic. The succedent late Tithonian–early Valanginian Buchia fauna-bearing Dong'anzhen Formation may be the earliest cover beds overlying the Raohe Accretionary Complex. Then, during the Early Cretaceous, the Nadanhada terrane received the deposition of the Aucellina bivalve fauna-bearing Dajiashan Group. This indicates paleogeographic differentiation between the Nadanhada terrane and the Tamba-Mino-Ashio terrane.