New high-resolution multibeam mapping images detail the southern part of Exuma Sound (Southeastern Bahamas), and its unchartered transition area to the deep abyssal plain of the Western North Atlantic, bounded by the Bahama Escarpment extending between San Salvador Island and Samana Cay. The transition area is locally referred to as Exuma Plateau. The newly established map reveals the detailed and complex morphology of a giant valley draining a long-lived carbonate platform from its upper slope down to the abyssal plain. This giant valley extends parallel to the slope of Long Island, Conception Island, and Rum Cay. It starts with a perched system flowing on top of a lower Cretaceous drowned main carbonate platform. The valley shows low sinuosity and is characterized by several bends and flow constrictions related to the presence of the small relict isolated platforms that kept alive longer than the main platform before drowning and merging tributaries. Turbidite levees on either side of the valley witness the pathway of multiple gravity flows, generated by upper slope over steepening around Exuma Sound through carbonate offbank transport, some of them locally > 15°, and resulting slumping. In addition, additional periplatform sediments are transported to the main valley through numerous secondary slope gullies and several kilometre-long tributaries, draining the upper slopes of cays and islands surrounding Exuma Plateau. Some of them form knickpoints indicating surincision of the main Exuma Valley which is consistent with an important lateral supply of the main Exuma Valley. Prior to reaching the abyssal plain, the main valley abruptly evolves into a deep canyon, 5 km in width at its origin and as much as 10 km wide when it meets the abyssal plain, through two major knickpoints named "chutes" with outsized height exceeding several hundred of meters in height. Both chutes are associated with plunge pools, as deep as 200-m. In the deepest pools, the flows generate a hydraulic jump and resulting sediment accumulation. When the canyon opens to the San Salvador abyssal plain, the narrow, deep, and strong flows release significant volume of coarsegrained calcareous sediments in numerous turbidite layers interbedded with fine mixed siliciclastic and carbonate sediments transported by the Western Boundary Undercurrent (WBUC) along the Bahama Escarpment. Carbonate gravity flows exiting the canyon decelerate at the abyssal plain level and construct a several-kilometre-wide coarse-grained deep-sea turbidite system with well-developed lobe-shape levees, partially modified by the flow of strong contour-currents along the Bahama Escarpment.

New high-quality multibeam data detail the morphology of the giant 135-km-long Great Abaco Canyon (GAC) located between Little Bahama Bank (LBB, Bahamas) and Blake Plateau. Knickpoints, chutes, and plunge pools mark the canyon main axis, which is parallel to the LBB margin. The canyon head covers a large area but does not represent the main source of the modern sediments. The material supplied through the LBB canyon systems originates below this head, which only shows erosive lineaments related to the pathway of currents running along the seafloor and restricted failure scars. Most of the sediment supply originates from the canyon sides. The northern canyon flank incises the Blake Plateau, which comprises contourites on top of a drowned Cretaceous carbonate platform. These deposits are susceptible to translational slides and form dissymmetric debris accumulations along the northern edge of the canyon. A large tributary drains the Blake Plateau. Two large tributaries connecting the southern flank of the GAC directly to the LBB upper slope form additional sources of sediments. Subbottom profiles suggest the presence of a sedimentary levee on the tributary canyon and of sediment gravity flow deposits. The GAC has been a permanent structure since the drowning of the Cretaceous platform, and its size and morphology are comparable to those of canyons in siliciclastic environments. The orientation of the GAC parallel to large-scale regional tectonic structures suggests a structural control. The size of the observed structures, especially plunge pools at the base of gigantic chutes, is unusual on Earth. The presence of deposits downflow of the pools suggests that the GAC results from or at least is maintained by persistent and sustained submarine gravity flows rather than by retrogressive erosion.

Numerous dense geodetic observations over recent decades reveal that faults can experience a wide range of slip velocities, ranging from stable slow aseismic creep to fast dynamic instability of earthquakes. In this spectrum of fault slip, slow earthquakes exhibit an intermediate behavior between purely steady aseismic creep and regular earthquakes (

We use the discrete element method to create numerical analogs to subduction megathrusts with natural roughness and heterogeneous fault friction. Boundary conditions simulate tectonic loading, inducing fault slip. Intermittently, slip develops into complex rupture events that include foreshocks, mainshocks, and aftershocks. We probe the kinematics and stress evolution of the fault zone to gain insight into the physical processes that govern these phenomena. Prolonged, localized differential stress drops precede dynamic failure, a phenomenon we attribute to the gradual unlocking of contacts as the fault dilates prior to rupture. Slip stability in our system appears to be governed primarily by geometrical phenomena, which allow both slow and fast slip to take place at the same areas along the fault. Similarities in slip behavior between simulated faults and real subduction zones affirm that modeled physical processes are also at work in nature.

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.