Abstract:

The Erlian Basin is a continental rifting basin which is constituted by faulted sags in the styles of graben and/or halfgraben controlled by NENNE striking normal faults and was filled by the Lower Cretaceous. A lot of faultedsags concentratedly distributed in three rifting zones extending in different directions (ManiteWulanchabu rift zone, Wunite rift zone, and ChuanjingTenggar rift zone), and a few faultedsags were scattered over the uplift around the rift zone in the Erlian Basin. The basement of basin was constructed by multicycle tectonism and geological process before the Cretaceous, which was of heterogeneity in crustal nature and had a variety of structure lines. The strong deformation zones were mounted with weak deformation blocks; the former included foldthrust zone, suture zone and accretionary wedge; the latter included magmatic rock bodies, magmatic arcs or micro continental blocks, etc. The distribution and structural style of faultedsags were closely related to basement structure. The rift zone is also the strong deformation zone of basement. The various directions in basement strong deformation zone have caused the difference of rift zone in structural style and their arrangement of faultedsags. ManiteWulanchabu rift zone which superimposed on the WuzhumoqinErlian curve foldthrust zone that projected to southeast direction is the orthogonal rifting structure chaining graben and/or halfgraben in NNENE striking in series. Wunite rift zone which superimposed on the ErlianHegenshan suture zone (mélange zone) in NEEstriking is of oblique rifting structural feature combining graben and/or halfgraben together in rightstep echelons. ChuanjingTenggar rift zone which superimposed on the WenduermiaoXinamulun suture zone and accretionary wedge of north boundary of North China Craton in EW striking has also the typical oblique rifting structural feature combining graben and/or halfgraben together in highangle echelons or parallel connection. The Early Cretaceous faulted sags within orthogonal rift zone included long narrow but deep graben and/or halfgraben. The Early Cretaceous faulted sags within oblique rift zone included short wide but shallow graben and/or halfgraben. Abovementioned geological features demonstrate that the distribution and structural style of faultedsags in Erlian Early Cretaceous basin was controlled by basement structure.

Key words: orthogonal rifting, oblique rifting, structural style, basement structure, Erlian Basin