Quaternary sedimentation over the Precambrian basement of Borborema Province (NE, Brazil): Tectonic and climatic controls

Abstract

This study characterizes the existence of Quaternary sediments in the Transversal Zone of the Borborema Province (Northeastern Brazil). The sediments comprise paleosoils, unconsolidated sands and gravel deposits, which overlie Precambrian basement rocks. The new data on these deposits includes sedimentological and stratigraphic aspects, and age definition through quartz optically stimulated luminescence (OSL) method. The outcrops were subdivided in two broad groups (named RL and Rca) referring to nearby towns where the samples were collected. OSL ages from the RL group provided ages between ca. 160.15 ± 38.26ka to 4.30 ± 2.18ka, whereas the sediments in the Rca group present OSL ages from 67.45 ± 18.24ka to 7.67 ± 2.74ka. The geochronological results reveal that these sediments were deposited during a time period from the Pleistocene to the Holocene. Deposits are chronocorrelated to Post-Barreiras (ca. 74-2ka in age), apart from the Barreiras Formation (ca. 25 to 17Ma in age), by an expressive hiatus in the Northeast Brazil. Our investigation suggest that the sediments, in the study area, are a reworking of crystalline basement and differs genetically from Post-Barreiras in the coastal zone, which are reworked from the Barreiras Formation. The combination of intense humid chemical weathering during the Pleistocene-Holocene influenced the quaternary deposition in the study area. In addition, the regional brittle tectonic reactivation of shear zones also during the Paleogene influenced the space of accommodation that allowed the deposition of these sediments.