EXPLANATORY NOTE

Abstract

This map is included as a large fold-out insert at the back of this volume. It is also available for download as a high-resolution PDF, for readers and institutions that have purchased the volume or subscribe to the Lyell Collection. The first version of this map came together in 2012 following the authors’ work reviewing the offshore basins of Mexico. In 2013/14 Mexico introduced sweeping changes to encourage foreign investment, ending Pemex’s 75-year monopoly over the nation’s oil and gas industry. Between 2014 and 2018 Mexico offered and awarded blocks in nine licence rounds, with each round releasing more data via the Cómision Nacional de Hidrocarburos (CNH) website. The end result is a compilation of eight years of work from a multitude of sources ranging from academia, the oil industry, government and independent research. The map covers the Mexican sector of the Gulf of Mexico and the adjacent onshore orogenic belts of the Mexican and Chiapas Fold and Thrust belts. It is intended to serve as a complementary document to the papers in this volume, and we have attempted to name all geological features that are mentioned, although some have probably eluded us. The main structural features displayed are faults, shear zones, folds and halokinetic bodies. The red (anticline) and green (syncline) fold hinges in the offshore serve to outline the Perdido Fold Belt in the north (Oligocene age gravity-induced), the Mexican Ridges Fold Belt in the central portion (Late Miocene to Recent gravity-induced) and the tectonically-induced arcuate fold and thrust pattern in the Sureste Basin which was generated by northward salt flow during the Chiapanecan orogeny (Davison 2020, this volume). Halokinetic bodies (light pink with an ‘L’ symbol) have been digitized from a number of publications and also our own interpretation from analysing the high-resolution bathymetry and from industry seismic coverage across the region. The darker pink-coloured Paleogene extrusive salt structures were interpreted from the publicly available seismic across the Comalcalco, Pilar Reforma-Akal and Macuspana subbasins. The salt basin outlines are shown as dashed pink lines, and were interpreted from many published and confidential seismic profiles. The extinct Oceanic Fracture Zones (curved north–south thick dashed black lines) and MidOcean Ridge segments (east–west red and black dashed lines) have been interpreted from vertical gravity gradient data (Sandwell et al. 2014) andmagnetic anomalies (Pindell et al. 2020, this volume). The ocean crust boundary has been interpreted as a dashed blue line, and passes from the offshore to the onshore in the Veracruz Basin (see Pindell et al. 2020, this volume for a similar interpretation). The onshore oceanic crust is overlain by.10 km of sediment, derived from the high-standing volcanic arcs and the basement massifs to the west. The Chicxulub impact crater is shown on the northern tip of the Yucatán peninsula (with dark blue rail-track lines). There is a remarkable semicircular alignment of cenotes, marked as dark blue spots on the map, which are mainly water-filled sink holes. These faithfully follow the southern outline of the impact crater. The edge of the Cretaceous Yucatán carbonate platform is also shown with a blue brick ornament. The carbonate shelf edge collapsed during the meteorite impact at 66 Ma, with debris flows developed down-dip which reach up to 400 m in thickness. Some of the oilfields are partially reservoired in the Chicxulub breccias. Oilfields are shown in green and gas fields in red, both sourced from the CNH. The oilfields in the Sureste Basin are oriented in a NE–SW trend parallel to the local Jurassic continental margin trend, where two of the world’s largest fields are located (Cantarell is marked on the map, and the nearby Kuh-Maloob-Zaap). Recent discoveries in the Perdido Fold Belt are shown; they are aligned in a NE–SW trend and cross the maritime boundary into the USA. Offshore and onshore well locations (from CNH) are displayed by black circles but are limited to exploration-only wells; production and development wells are not displayed. The surface geology comprises multiple references, including the Servicio Geológico Mexicano (2006 1:500 000 Geological Map Series), Padilla y Sanchez et al. (2013), French and Schenk (2004)