--> Late Cretaceous-Paleogene Foreland Sediment-Dispersal Systems in Northern and Eastern Mexico: Interpretations From Preliminary Detrital-Zircon Analysis

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Late Cretaceous-Paleogene Foreland Sediment-Dispersal Systems in Northern and Eastern Mexico: Interpretations From Preliminary Detrital-Zircon Analysis

Abstract

Upper Cretaceous-Paleogene stratigraphy of the Mexican foreland-basin system broadly resembles that of the Alpine foreland basin in that both contain initial deepwater (flysch) deposits overlain by younger molasse-type deposits. In the Parras and La Popa basins of northern Mexico, Turonian-Santonian deepwater successions are overlain by shallow-marine and continental deposits of the Maastrichtian-Eocene Difunta Group. Similar molasse deposits are absent above deformed turbidites in the Mesa Central of north-central Mexico, where shallow-water strata may have been eroded from the thrust orogen. In the Tampico-Misantla basin of eastern Mexico, deepwater deposition persisted into the early Eocene, but molasse deposition never took place. Sediment delivery among these broadly correlative successions, the extent of their drainage basins, and locations of their depositional termini in and near the Gulf of Mexico basin are critical unresolved questions regarding the Cretaceous paleogeography of Mexico. New detrital-zircon data indicate that sediment sources for Mesa Central flysch deposits lay as far away as the SW United States, but that those sediment-delivery systems never connected as far south as the Tampico-Misantla basin. Detrital zircon populations in a single sample of flysch in Zacatecas and six Difunta samples from the Parras and La Popa basins contain 1.7–1.6 Ga and 1.4 Ga zircon populations characteristic of SW Laurentian basement. These preliminary data suggest that Turonian-Santonian axial rivers debouched SSE into deep water of the Mexican seaway basin prior to late Campanian time, when the advancing orogen deflected axial drainage eastward along the Sierra Madre foredeep toward Monterrey. Flysch deposits of central Mexico, recorded by a sample of the Soyatal Fm, lack Laurentian grains, indicating local derivation from accreted terranes directly to the west. A sample of Paleocene turbidites from the Puskon #1 well in the distal part of the Tampico-Misantla basin similarly lacks Laurentian zircons, and is dominated by grains ranging 1.3–1.1 Ga and 144–66 Ma, likely derived from exposed Grenville basement and the Cretaceous magmatic arc of southern Mexico, respectively. Because axial drainage recorded by the Difunta Group did not deliver Laurentian sediment into the Tampico-Misantla basin, it is likely that this voluminous Wilcox-equivalent dispersal system instead spilled eastward across the Tamaulipas arch into the NW Gulf of Mexico.