COMPOSITIONAL ANALYSIS AND SEDIMENTARY RECYCLING EVIDENCES ASSOCIATED TO UNCONFORMITIES IN THE NORTHEASTERN MEXICO, AN LATE TRIASSIC-EARLY CRETACEOUS EXAMPLE

The stratigraphic column of the Monterrey Tough in the northeastern Mexico comprises Late Triassic to Early Cretaceous clastic sequences limited by a series of angular-erosive unconformities. This work analyses the sequence composition aiming to comprehend the recycling-cannibalism process and the compositional variation between source-lands and its relation to unconformities.

The framework petrography of the clastic sediments allows to demonstrate three recycling periods or important source-rock addition by plotting QmFL diagram: 1) Upper Triassic (Qm₇₀F₁₀L₂₀), high-mid-grade metamorphic source rock erosion assuming high-grade transportation by its >Qm content; 2) Early Jurassic (Qm₄₀F₂₂L₃₈), period with maximum exhumation of volcanic and metamorphic rocks; and 3) Early Cretaceous (Qm₅₆F₃₁Lt₁₃), shot lasting exhumation period mainly of granites or granodiorites, volcanic rocks and in less amount low-grade metamorphic rocks.

This interpretations are supported by applying index compositional varietal relations and recycling (F/Qt, Qp/Qt, Lm/Lv, Ls/Qm), that proof the relationship between the recycling and cannibalism processes and changes in source are type.

As a whole, interpretations among framework (QFL) and compositional indexes validate the evolution of the recycling process; allowing to propose an empirical sedimentary recycling index (SeReIn).

The SeReIn has been applied into three different cases, demonstrating sensibility in facies variations (e.g., storm deposits versus sand flat), grain size (e.g., tidal channels), and the genetic implication for uncoformities within column for the northeastern Mexico (informational cannibalism versus allocyclic controls).