Late Strike-slip Movements Research Articles

Hoggar geochronology: a historical review of published isotopic data

A dataset of more than 400 isotopic ages on the Hoggar Shield, published from 1963 to 2017, was obtained by increasingly precise isotopic dating techniques and low-temperature thermochronology. Data were arranged by eras and terranes and classified in two categories “before 1980” and “after 1980”. They illustrate the protracted geological history of the Hoggar Shield. The first continental nuclei were formed 3.5–2.5 Ga ago during the Archean, with high-grade metamorphic and associated magmatic episodes. A second group of continental terranes was created 2.40–1.75 Ga ago during the Paleoproterozoic, with Eburnean orogenic episodes marked by reworking of older Archean terranes associated with juvenile terranes. After the 1.80–0.90 Ga long period of quiescence, the 870–540 Ma Neoproterozoic times were characterized by Pan-African episodes, with early overthrusting of eclogitic nappes and late strike-slip movements along north-south trending shear zones, high-grade metamorphism and anatexis, emplacement of large granitoid batholiths followed by complexes of the Taourirt igneous suite. Cambrian hydrothermal activity evidences either a slow cooling process, or more likely discrete thermal pulses. After scarce Carboniferous mafic magmatism, the Mesozoic and the beginning of the Cenozoic constituted a period of quiescence marked by subsidence and burial after the Early Cretaceous. Low-temperature chronology records episodes of alternating subsidence and exhumation. Widespread Eocene exhumation predated volcanic activity beginning in the Late Eocene and continuing until recent times, in association with Africa–Europe convergence processes.

How much confidence can be conferred on tectonic maps of continental shelves? The Cantabrian-Fault case

The Cantabrian Fault is a long-lived crustal fault, 320 km long on land and extending more than 150 km seawards within the Bay of Biscay, which separates different geodynamic domains. Due to its sub-vertical dip and late strike slip movement is poorly evidenced in the shelf and it has been traditionally mapped following the strike of the deepest submarine canyon in the north Atlantic (~4.600 m drop). Based on multichannel reflection data, seismicity from a thirty year period, a GIS model, and the support of detailed field mapping onshore, the fault has been traced more accurately. Surprisingly, it presents a much more E-W strike than mapped before, and shows a splay fault termination never previously assessed. Moreover, the fault acts as a seismic barrier within the actual stress field of Iberia. Collaterally, a large submarine landslide (2000 km2) associated with its seismicity has been discovered, providing a further argument to support the newly proposed trace of the fault.