Sequence stratigraphy of the mixed wave-tidal-dominated Mesoproterozoic sedimentary succession in Chapada Diamantina Basin, Espinhaco supergroup- Ne/Brazil

摘要

Although the application of the sequence stratigraphy concepts in the Phanerozoic basins is well constrained, few studies are available on the Proterozoic successions to better understand their basin infill using modern stratigraphic concepts. This work aims to provide a well-constrained application of sequence stratigraphic concepts in Proterozoic sedimentary succession, taking as a case study the well-preserved Mesoproterozoic shallow marine Morro do Chapeu Formation. This records the accumulation in a sag-phase of the intracontinental Espinhaco basin developed into Congo-Sao Francisco Paleoplate. Two third-order depositional sequences have been identified, separated by a regional subaerial unconformity. The lower third-order sequence includes the succession of lowstand, transgressive, and highstand systems tracts (LST, TST, and HST), whereas the upper third-order sequence only preserves LST and TST. The sedimentary record is composed of alluvial fan, wave reworked fan-delta, unconfined sheetfioods, subtidal deposits and wavy-dominated shallow marine sediments. The relative sea level variation was the main control of sedimentation during the sag phase on the Upper Espinhaco Megasequence. This study presents an exceptional example of stratigraphic evolution during Proterozoic, increasing the knowledge about sedimentation patterns, that should be compared with other Precambrian basins formed in similar tectonic settings.