Sedimentology and stratigraphy of new outcrops of Silurian glaciomarine strata in the Presidente Figueiredo region, northwestern margin of the Amazonas Basin. (August 2018)

• Record Type: Journal Article
• Authors: Rincón Cuervo, Holman Dario; Soares, Emílio Alberto Amaral; Caputo, Mario Vicente; Dino, Rodolfo
• Is Part Of: Journal of South American earth sciences. Volume 85(2018)
• Page Start: 43
• Page End: 56
• Publication Date: 2018-08
• Subjects: Littoral and glacial facies -- Llandoverian diamictites -- Early silurian glaciation; Geology -- Latin America -- Periodicals; Earth sciences -- Latin America -- Periodicals; Geology -- Antarctica -- Periodicals; Earth sciences -- Antarctica -- Periodicals; Geology -- Caribbean Area -- Periodicals; Earth sciences -- Caribbean Area -- Periodicals; Géologie -- Amérique latine -- Périodiques; Sciences de la terre -- Amérique latine -- Périodiques; Géologie -- Antarctique -- Périodiques; Sciences de la terre -- Antarctique -- Périodiques; Géologie -- Caraïbes (Région) -- Périodiques; Sciences de la terre -- Caraïbes (Région) -- Périodiques; Earth sciences; Geology; Antarctica; Caribbean Area; Latin America; Periodicals; 550.5
• DOI: 10.1016/j.jsames.2018.04.023
• Languages: English
• ISSNs: 0895-9811

Abstract

Abstract: New occurrences of Lower Silurian glaciomarine outcrops were identified in a belt about 80 kilometers long in the municipality of Presidente Figueiredo on the northern flank of the Amazonas Basin. This narrow belt of Paleozoic sedimentary rocks has a general E-W trend and includes Ordovician to Early Devonian and Middle Devonian to Early Mississippian sedimentary sequences. The belt is limited to the north by the Neoproterozoic Prosperança Formation and Paleoproterozoic igneous and metamorphic rocks of the Central Amazonia Province. To the south, the Paleozoic beds are bounded by Neogene sediments of the Alter do Chão Formation. Outcrops were studied along the BR-174 and AM-240 highways, secondary roads and river banks of the region, where nine distinct sedimentary facies allowed definition of shoreface, foreshore and glaciomarine environments. Shoreface deposits are the most abundant, represented by five distinct facies, and are associated with two foreshore facies. Included in marine strata are two levels of massive, coarse diamictite and laminated facies consisting predominantly of clasts of quartz-sandstone, quartz and mudstone immersed in a fine clay-silty-fine sandy matrix. The massive aspect of the diamictites and the presence of faceted and striated pebbles, associated with palynological data, allowed us to relate them to a Middle-Late Llandoverian glacial event, which was first recognized in the subsurface of the Amazonas Basin in 1971.