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Sequence stratigraphy of Jurassic-Cretaceous boundary strata in Luanping,Northern Hebei,China |
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| Authors: | |
| Institution: | 1. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China 2. Shijiazhuang Economic College, Shijiazhuang 065000, China 3. Tianjin Institute of Geology and Mineral Resources, Tianjin 300170, China |
| Abstract: | A sediment-continuous section of Jurassic-Cretaceous (J-K) boundary strata was found in Zhangjiagou of Luanping, northern Hebei Province, China. The boundary strata were systematically divided into 5 sequences, 13 subsequences and 139 parasequences by sedimentary cyclicities and facies analysis. According to stable time-ranges of subsequences and parasequences, some boundary ages can be marked as 142.90 Ma of the SQⅠ (Dabeigou Fm)basal bound, 141.16 Ma of the SQ Ⅱ basal bound, 140.00 Ma of the SQ Ⅲ (Dadianzi Fm) basal bound, 138.24 Ma of the SQ Ⅵ (Zhangjiagou Fm) basal bound and 135.34 Ma of the SQ Ⅴ (Zhangjiagou Fm) top-bound. A sequence-stratigraphic framework of the Dabeigou- Zhangjiagou Fms has been constructed by tracing sequence-bounds, marker-beds and fossil zones. The basin-development and tectonicactivities are studied based on sequence-stratigraphic evidence. 5 sequences represent 5 tectonic cycles and all the 6 sequence-bounds reflect tectonic activities.Tectonic activities clearly influence the basin-development that can be divided into 3 stages in the J-K transitional period. Each stage consists of a down-faulting-rising process, i.e. from strongly rising of basin-bottom, then violently faulting down (with volcanic eruptions) and to gently rising.The development shows a pattern of bottom down-faulting with basin narrowing and rising with spreading. |
| Keywords: | sequence stratigraphy terrestrial stratotype Jurassic-Cretaceous bound |
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