Phanerozoic cooling events in the continental rims of the Central Atlantic Ocean.

Abstract

In this review, we have digitized and georeferenced over 7000 Low-Temperature Thermochronology (LTT) data points and 750 Time-Temperature Modelling (TTM) results from 252 published works. The study area includes the continental crusts adjacent to the rifted margins (~Late Triassic to Early Jurassic) of the Central Atlantic Ocean and its direct neighbours. Our main intention is to map out the thermal cooling events as recorded by LTT data and as illustrated by TTM results. The time interval targeted in this review is the Phanerozoic (i.e., 540 to 0Ma), which is possible thanks to LTT ages spanning this entire period in the study area. It allows us to investigate the thermal evolution of the continental rims of the Central Atlantic Ocean at an unprecedented scale. In rifted margins and their shoulders, a debate exists whether the LTT-recorded cooling is the results of post-rift erosional exhumation or post-heating thermal relaxation, especially for the area directly in the vicinity of the paleo-rift zone. We therefore devised a short workflow to examine these propositions by filtering out the LTT dataset and spatially plotting the LTT ages. Furthermore, we investigate the relationship between LTT ages and distance from the Continent-Ocean Boundary/Transition Zone. LTT ages alone have often been described as bearing little geological meaning, thus requiring to run TTM in order to reconstruct the thermal/geological history, as several factors are to be taken into account in the thermal history reconstruction. Here, we examine whether a statistically significant LTT dataset can serve as a proxy in the reconstruction of cooling events. To this end, we compare peaks of LTT cooling ages and of TTM cooling event. Our investigation reveals that i) generalised cooling occurred in the pre-, syn-, and post-rift phases of the Central Atlantic, ii) there is a clear LTT age oceanward youngening trend, iii) the lack of LTT age with a syn-rift signal within ~500km along the shorelines suggests erosional exhumation (i.e., vertical movements) as main driver of the cooling, and iv) large LTT datasets bear meaning on the cooling events and thus on vertical movements, at least in this case studies in the rims of the Central Atlantic Ocean.