Diego Villagómez

We present the first Lu–Hf dating on high-pressure/ultra-high-pressure mineral assemblages in eclogitic rocks from Puerto Cabello, northern central Venezuela. The rocks characterize the Carayaca terrane of the Cordillera de la Costa (CdlC) along the coast and faults bounding the valley of Caracas City. The new late Eocene peak metamorphic ages (38–36 Ma) pertain to Eocene subduction of Proto-Caribbean crust to 80–100 km depth beneath the Caribbean forearc as the latter collided with Venezuela. The ages break the formerly assumed correlation with Margarita Island eclogites and Villa de Cura blueschists of southern CdlC. The distinct histories of these high-pressure/low-temperature metamorphic suites and the Etpana terrane in Guajira, Colombia, constrain depth geometries in regional evolutionary models. By integrating our results with an updated view of synorogenic sedimentation in the Piemontine belt, southern CdlC, we propose crustal scale present and evolutionary cross-sections and maps for the development and exhumation history of the Carayaca terrane and the greater CdlC. In addition, this synthesis concludes that Caribbean collision was preceded by Paleocene incipient subduction and rift fault inversion along Venezuela's Proto-Caribbean margin, exposing Caucagua–El Tinaco belt basement to erosion as recorded in Los Cajones Formation flysch of the Piemontine belt.

This work presents new apatite fission track LA–ICP–MS (Laser Ablation Inductively Coupled Plasma Mass Spectrometry) data from Mid–Late Paleozoic rocks, which form the substratum of the Swiss Jura mountains (the Tabular Jura and the Jura fold-and-thrust belt) and the northern margin of the Swiss Molasse Basin. Samples were collected from cores of deep boreholes drilled in North Switzerland in the 1980s, which reached the crystalline basement. Our thermochronological data show that the region experienced a multi-cycle history of heating and cooling that we ascribe to burial and exhumation, respectively. Sedimentation in the Swiss Jura Mountains occurred continuously from Early Triassic to Early Cretaceous, leading to the deposition of maximum 2 km of sediments. Subsequently, less than 1 km of Lower Cretaceous and Upper Jurassic sediments were slowly eroded during the Late Cretaceous, plausibly as a consequence of the northward migration of the forebulge of the neo-forming North Alpine Foreland Basin. Following this event, the whole region remained relatively stable throughout the Paleogene. Our data show that the Tabular Jura region resumed exhumation at low rates in early–middle Miocene times (≈20–15 Ma), whereas exhumation in the Jura fold-and-thrust belt probably re-started later, in the late Miocene (≈10–5 Ma). Erosional exhumation likely continues to the present day. Despite sampling limitations, our thermochronological data record discrete periods of slow cooling (rates of about 1°C/My), which might preclude models of elevated cooling (due to intense erosion) in the Jura Mountains during the Miocene. The denudation (≈1 km) of the Tabular Jura region and the Jura fold-and-thrust belt (≈500 m) has provided sediments to the Swiss Molasse Basin since at least 20 Ma. The southward migration of deformation in the Jura mountains suggests that the molasse basin started to uplift and exhume only after 5 Ma, as suggested also by previous authors. The data presented here show that the deformation of the whole region is occurring in an out-of-sequence trend, which is more likely associated with the reactivation of thrust faults beneath the foreland basin. This deformation trend suggests that tectonics is the most determinant factor controlling denudation and exhumation of the region, whereas the recently proposed “climate-induced exhumation” mechanism might play a secondary role.

We present an updated, internally consistent synthesis of the Permo-Triassic assembly and Mesozoic evolution of the Gulf of Mexico, Mexico, Florida–Bahamas and northern South America (Guiana margin and northern Andes), incorporating advances at regional, field and geochronological levels. The recently determined Bajocian age for salt deposition (using ⁸⁷ Sr/ ⁸⁶ Sr isotopes) is integrated by modifying the plate kinematic framework with a new Equatorial Atlantic reconstruction that expands the gap between the Americas by 180 km over many kinematic frameworks. NW–SE synrift lithospheric extension along western Florida–Bahamas is estimated at 40%, implying thinned continental crust beneath Great Bank, Bahamas, the conjugate for the Guianas Basin margin. In cordilleran Mexico (excluding the Yucatán Block), we propose two new means by which continental crust migrated into the ‘Colombian overlap position’ of Pangaean reconstructions. The first involved Jurassic–earliest Cretaceous sinistral displacement of the Oaxaca Block along a NW–SE ‘North Oaxaca Transfer’ through or adjacent to the Cuicateco Belt. The second applies to the continental crust in eastern Mexico to the north of Cuicateco, a region we refer to as ‘peninsular Mexico’. There, most Mesozoic basement faults trend NW–SE, and the common occurrence of Permian mid-crustal anatectic basement directly beneath Mesozoic red beds, salt and marine strata suggests extreme extension prior to the onset of sedimentation. Because these Mesozoic sedimentary sections typically sum to 3–8 km in thickness, the post-rift crust of peninsular Mexico probably averaged about 25 km in thickness before later orogenesis. Our reconstructions suggest that this Triassic–Middle Jurassic extension approached 100%, beginning with overthickened Alleghanian (Permian) crust about 50 km in thickness in palaeo-northern Mexico, and was accompanied by a significant sinistral component broadly distributed across the rift array. The updated model provides an exploration and kinematic framework for the entire region.

A database of 134 apatite fission track (AFT), and apatite and zircon (U–Th)/He analyses has been assembled for eastern Mexico. Most of these samples have reset ages and track lengths reflecting rapid cooling. Time–temperature histories were modelled for 99 localities, and were converted to depth using a constant gradient of 30°C km ⁻¹ . Maps of these results reveal smooth temperature patterns in space and time, indicating that heating was due to regional burial rather than hydrothermal circulation. Cooling began by 90 Ma in the west and 50 Ma along the eastern edge of the Sierra Madre Oriental. These ages mimic the duration of the Mexican Orogeny, which verifies that most of these AFT ages have event significance. The elongate Mayrán Basin, a part of the Mexican foreland basin system, formed and grew across and above the eastern toe of the active Sierra Madre Oriental. This basin subsided between at least 70 and c. 40 Ma, and reached a minimum depth of 6 km. It was a both a catchment and routing system for sediment from US and Mexican sources. The shape of the basin suggests that early outflow was directed through the Burgos Basin into the Gulf of Mexico (GoM). By 50 Ma, some outflow potentially routed southwards through the Tampico Misantla Basin area. The Mayrán Basin subsided until 40 Ma, and then began to uplift and erode. This inversion mobilized the stored sediment and redeposited it into the GoM, filling the offshore Bravo Trough. Volcanism swept eastwards between 90 and 40 Ma, driven by northeastward-directed flat-slab subduction, which may also have driven the contraction. Local subsidence during contraction suggests there was dynamic pull-down created by the underriding flat slab. Subsidence ceased at c. 40 Ma, as volcanism swept back westward and asthenosphere replaced the flat slab. The crust rebounded, creating an ensuing period of massive erosion which peaked around 20 Ma. Southern Mexico was relatively quiet until rapid uplift began in Oaxaca in late Oligocene–early Miocene time. Uplift progressed eastwards to the Chiapas Massif in the late Miocene, commensurate with the eastward translation of the Chortis Block.

The Miocene Nanchital conglomerate of the western Chiapas Foldbelt is the coarsest terrigenous clastic depositional Cenozoic unit of the region, probably comprising more proximal sections of hydrocarbon-rich slope-fan reservoirs found in the more distal Sureste Basin of the southern Gulf of Mexico fringe. Traditionally, the felsic igneous and metamorphic components of the conglomerate were assumed to derive from the Permian basement of the nearby Chiapas Massif. However, zircon U–Pb dating of five Nanchital conglomerate clasts from the Chiapas Foldbelt as well as several igneous exposures in SW Tehuantepec indicates that the Nanchital conglomerate's catchment area included the western Isthmus of Tehuantepec for late Middle Miocene and possibly early Late Miocene time, after which the more proximal Chiapas Massif and Chiapas Foldbelt likely became dominant. This study suggests that traditional concerns over the limited extent of quartz-rich clastic source areas feeding terrigenous clastic reservoirs in the Sureste Basin might be overly pessimistic. We propose a temporal framework for viewing Neogene and Quaternary clastic supply to the southern Gulf of Mexico.