ABSTRACT New K-feldspar 40 Ar/ 39 Ar and apatite fission-track thermochronological data from the crystalline basement of the western Gulf of Mexico (basement core samples from Tamaulipas Arch, Tuxpan, and Jalapa–Santa Ana highs) and K-feldspar 40 Ar/ 39 Ar from field samples of the Chiapas Massif in southern Mexico provide valuable information on the tectonic history of the region, namely, the rifting and postrifting stages of evolution in the Gulf of Mexico. The onset of rifting was probably as early as ca. 216 Ma and was characterized by extensional faulting that led to cooling of the basement footwall blocks by tectonic unroofing. The Tamaulipas Arch and the Jalapa–Santa Ana High were unroofed and cooled until ca. 160 Ma, whereas rocks from the Chiapas Massif were probably affected only until ca. 180 Ma. The thermochronological data suggest that the Tamaulipas Arch and the Chiapas Massif may have been footwalls to low-angle detachments prior to ca. 180 Ma. By ca. 180 Ma, the Chiapas Massif was arguably attached to Yucatán. Rotation of the Yucatán block (and Chiapas Massif) probably started at ca. 167 Ma and unroofed (exhumed) the Tamaulipas Arch very quickly until 155 Ma, when it was unconformably covered by Kimmeridgian sediments along its flanks. The Tamaulipas Arch was progressively buried until the Eocene (ca. 40 Ma), when it was uplifted, and a portion of its sedimentary cover was eroded. A second pulse of uplift occurred in the late Miocene. Our thermochronological data also show that there are along-strike variations in the vertical movements experienced by the Tamaulipas Arch since the Jurassic. This can have important implications for oil maturation of the source rocks in the region, as there might be zones that remained within the oil window for significant amounts of time.

The recent discovery of the direct link between Deccan volcanism and the end-Cretaceous mass extinction also links volcanism to the late Maastrichtian rapid global warming, high environmental stress, and the delayed recovery in the early Danian. In comparison, three decades of research on the Chicxulub impact have failed to account for long-term climatic and environmental changes or prove a coincidence with the mass extinction. A review of Deccan volcanism and the best age estimate for the Chicxulub impact provides a new perspective on the causes for the end-Cretaceous mass extinction and supports an integrated Deccan-Chicxulub scenario. This scenario takes into consideration climate warming and cooling, sea-level changes, erosion, weathering, ocean acidification, high-stress environments with opportunistic species blooms, the mass extinction, and delayed postextinction recovery. The crisis began in C29r (upper CF2 to lower CF1) with rapid global warming of 4 °C in the oceans and 8 °C on land, commonly attributed to Deccan phase 2 eruptions. The Chicxulub impact occurred during this warm event (about 100–150 k.y. before the mass extinction) based on the stratigraphically oldest impact spherule layer in NE Mexico, Texas, and Yucatan crater core Yaxcopoil-1. It likely exacerbated climate warming and may have intensified Deccan eruptions. The reworked spherule layers at the base of the sandstone complex in NE Mexico and Texas were deposited in the upper half of CF1, ~50–80 k.y. before the Cretaceous-Tertiary (K-T) boundary. This sandstone complex, commonly interpreted as impact tsunami deposits of K-T boundary age, was deposited during climate cooling, low sea level, and intensified currents, leading to erosion of nearshore areas (including Chicxulub impact spherules), transport, and redeposition via submarine channels into deeper waters. Renewed climate warming during the last ~50 k.y. of the Maastrichtian correlates with at least four rapid, massive volcanic eruptions known as the longest lava flows on Earth that ended with the mass extinction, probably due to runaway effects. The kill mechanism was likely ocean acidification resulting in the carbonate crisis commonly considered to be the primary cause for four of the five Phanerozoic mass extinctions.

The Granjeno Schist of northeastern México is the oldest component of the Sierra Madre terrane and comprises polydeformed, pelitic metasedimentary and metavolcaniclastic rocks that enclose lenses of serpentinite-metagabbro. This low-grade Paleozoic assemblage is exposed in the core of a NNW-trending frontal anticline of the Laramide fold-thrust belt where it is tectonically juxtaposed against ca. 1 Ga granulites of the Novillo Gneiss. Silurian strata that unconformably overlie the Novillo Gneiss are unmetamorphosed and contain fauna of Gondwanan affinity. LA-ICPMS (laser ablation inductively coupled plasma mass spectroscopy)U-Pb ages for detrital zircons from a Granjeno phyllite yield age populations that cluster in the ranges ca. 1375–880 Ma, ca. 650–525 Ma, and ca. 460–435 Ma and slightly discordant grains with individual ages of ca. 1435 Ma, ca. 1640 Ma, ca. 2105 Ma, and ca. 2730 Ma. The youngest detrital zircon indicates a maximum depositional age for the Granjeno Schist of ca. 435 Ma (Lower Silurian). Detrital zircons of Neoproterozoic–Cambrian age suggest a provenance in the Maya terrane beneath the Yucatan Peninsula or the Brasiliano orogens of South America, and a source for the detrital zircons of Ordovician–Silurian age is present in the Acatlán Complex of southern México. Provenance of the Mesoproterozoic detrital zircons is likely to have been the adjacent Novillo Gneiss, which has yielded ages of ca. 990–980 Ma, ca. 1035–1010 Ma, and ca. 1235–1115 Ma. These detrital ages closely match those recorded from the Cosoltepec Formation of the Acatlán Complex and support correlation of the two units, which are both interpreted to be vestiges of the southern margin of the Rheic Ocean.