Luminescence signals of quartz and feldspar as new methods for stratigraphic discrimination and provenance analysis of siliciclastic successions: The case of the Parnaíba Basin (Brazil) of West Gondwana

Abstract

AbstractLuminescence characteristics of quartz and feldspar allow to discriminate sediments from different source areas. Particularly, sensitivity of optically stimulated luminescence (OSL) and thermoluminescence (TL) signals of quartz and infrared‐stimulated luminescence (IRSL) of feldspar from Quaternary sediments has been used for provenance analysis. These properties change due to source area denudation rates and sediment reworking, which drive the number of burial irradiation‐solar exposure cycles of sediment grains in surface systems. Here, we use for the first time a similar approach to interpret the geomorphic conditions of source areas of Silurian to Triassic siliciclastic sedimentary units of the intracratonic Parnaíba Basin in northeast Brazil. Luminescence measurements were performed on sand grains, and statistical tests were applied to evaluate differences in luminescence properties within and across stratigraphic units. We explored the position of well‐known “110°C” (TL110) and “325°C” (TL325) TL peaks of quartz as proxies to discriminate stratigraphic units with similar lithological assemblages. OSL and TL sensitivities as well as the dominance of the so‐called fast OSL component increase from Silurian to Triassic sedimentary units, while the IRSL sensitivity decreases towards younger stratigraphic units. These patterns point to source areas with decreasing denudation rate and higher sediment recycling over basin filling time, leading to decreasing feldspar concentration and quartz luminescence sensitisation. Major changes in luminescence properties coincide with regional unconformities. This is attributed to physical landscape changes leading to shifts in the relief of source areas and basin sediment recycling. The TL110peak position is similar across stratigraphic units, but the TL325peak position has significant variation, with values between 324°C and 334°C, allowing its use for stratigraphic discrimination. Changes in OSL and TL characteristics of quartz sediment grains are preserved during long‐term burial (108 Ma), representing a new tool for interpreting basin evolution and to perform stratigraphic analysis of ancient siliciclastic successions.