44-17 Provenance of the Sepur-Soyaló turbidites as a record of the Late Cretaceous–Paleogene North American–Caribbean collision in Guatemala, Belize, and Chiapas (Mexico)

Abstract:

The Sepur-Soyaló turbidite deposits of the southern Maya block record Maastrichtian–Paleocene deposition in an underfilled foreland basin, produced by flexural loading associated with collision between the Greater Antilles Arc (Caribbean plate) and the North American continental passive margin.

Foreland basin conditions are first recorded in western and central Guatemala, where thin, fine-grained basal turbidites accumulated over latest Campanian platform limestone. In central Guatemala, stratigraphic relations and maximum depositional ages (72–67 Ma) indicate a Maastrichtian age for these turbidite deposits. Subsequent orogenic growth expanded the underfilled basin northward into northern Guatemala, Belize, and Chiapas. Here, turbidite deposition is constrained to the Paleocene, as turbidites overlie Maastrichtian limestone and K/Pg Chicxulub impact-related breccias, and detrital zircon maximum depositional ages range from 64 Ma to 59 Ma.

Maastrichtian turbidite sandstones are dominated by detritus consistent with calcareous and volcanic sources, and by a prevailing Cretaceous detrital zircon U-Pb age group (134–67 Ma) whose grains show igneous textures under cathodoluminescence. We surmise that the calcareous detritus was derived from Upper Cretaceous platforms in the southern Maya block and from carbonate platforms fringing the Greater Antilles Arc, while the igneous material was derived from the arc itself (extinct during the collision) and from the post-collisional volcanic belt produced in Jamaica and the Nicaragua Rise following subduction polarity reversal. In contrast, Paleocene turbidite sandstones are characterized by a highly heterogeneous provenance, including serpentinite and other metamorphic lithics, detrital glaucophane, and pre-Cretaceous detrital zircon age groups (1370–780 Ma; 480–420 Ma; 297–202 Ma), as well as detrital material related to the extinct arc, the post-collisional arc, and the Cretaceous platforms. We surmise that ultramafic nappes, high-pressure belts, Maya block continental-basement units, and recycled sedimentary successions of the passive margin became incorporated into the orogen during the Paleocene.

Sepur-Soyaló sandstone provenance data indicate a transition from a homogeneous sediment source in the Maastrichtian to more heterogeneous sources in the Paleocene, suggesting progressive unroofing of the orogen that eventually exhumed ultramafic nappes, metamorphic complexes, and sedimentary cover deposited on Maya block crust.

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