Quaternary deposits in the Serra da Capivara National Park and surrounding area, Southeastern Piauí state, Brazil

Abstract

Serra da Capivara National Park and surrounding areas in Southeastern Piauí State (Brazil) were subjected to morphostratigraphical, sedimentological, and geochronological studies about superficial deposits in order to interpret quaternary paleoenvironmental events. The following sedimentary deposits associated with morphostructural units were identified: colluvial fans at Serra Branca Valley and Structural Staircases, and eluvial-colluvial deposits at Reverse of the Cuesta. There are also colluvial and alluvial deposits outside Serra da Capivara National Park. Many colluvial and alluvial deposits are contemporaneous and indicate a semiarid climate. According to luminescence dating (thermoluminescence and optically stimulated luminescence), the present landscape evolution began around 436 ± 51.5 ka when the Piauí River deposited clayey sediments. From 296.55 ± 46.95 ka to 116.3 ± 19.52 ka, the fluvial channel likely exhibited a braided pattern and deposited sand and gravel bars. Penecontemporaneous sands and muds with ages ranging from 202.75 ± 32.81 ka, 135 ± 16.4 ka to 117 ± 14.5 ka were deposited on Serra da Capivara National Park hillslopes. A colluviation episode occurred between 84.7 ± 13.4 ka to 76.2 ± 9.35 ka, which lacks correlatable alluvial deposits. In the Northern hemisphere last glacial maximum, the colluviation and alluviation processes intensified. These depositional processes likely occurred between 15.8 ± 1.9 and 10.35 ± 1.76 ka, during the Holocene-Pleistocene transition.