Characteristics and sedimentary geological significance of tempestites in first member of Lower Cambrian Canglangpu Formation in north central Sichuan Basin

Abstract

Tempestite has been discovered in the Lower Cambrian Canglangpu Formation in the north central Sichuan Basin. However, there has been limited research on storm sedimentation and the Lower Cambrian sedimentary environments, ancient geography, and ancient sedimentary geomorphology in this region. By conducting detailed core observations and thin section identifications, the storm sedimentation sequence and sedimentation model of the Canglangpu Formation have been investigated, revealing its geological significance. Various storm sedimentation structures, such as gravel sections, graded sections, parallel laminated sections, and hummocky cross-stratifications (HCS), are present in the Canglangpu Formation. The tempestites within this formation can be categorized into five types of storm sedimentation sequences: Sequence Ⅰ includes gravel sections (A), parallel laminatedsections (C), and HCS (D) above the fair-weather wave base (FWB). Sequence Ⅱ comprises parallel laminated section (C), HCS (D), and horizontally laminated mudstone section (E) deposited near the storm wave base (SWB). Sequence Ⅲ includes scouring-fill structures and gravel section (A), as well as a graded section (B) deposited between the fair-weather wave base (FWB) and SWB. Sequence Ⅳ is characterized by a graded section (B) and parallel laminated section (C) located far from the storm center, above and near SWB. Sequence Ⅴ consists of scouring-fill structures and gravel section (A) located between the mean sea level (MSL) and FWB, close to FWB. The analysis of tempestites in north central Sichuan Basin suggests that the initial member of the Canglangpu Formation was deposited on the shelf-ramp-platform margin and shelf, indicating that the Upper Yangtze Plate was situated in a low latitude region during the sedimentation period of the Canglangpu Formation. This information provides valuable insights into lithofacies paleogeography reconstruction. Storm events have resulted in the formation of storm mudflats in the study area, which are favorable for reservoir development. The investigation of storms in the Canglangpu Formation aids in predicting the distribution of shoal facies in the study area.

Keywords

• storm sedimentation
• sedimentation model
• sedimentation sequence
• tempestite
• canglangpu formation
• lower cambrian
• north central sichuan basin