Plate convergence, consumption, collision, coupling, capture, and formation of mantle waves—Linkages to global orogenesis and epeirogeny

Abstract

Widespread episodes of major contractional orogenesis correlate commonly with ages of high-pressure eclogitic rocks formed during bottom-driven, induced subduction of crustal terranes. Rapid exhumation of the deeply emplaced crust has led to the development of the concept of a “tectonic dunk.” The dunk process is a hallmark component of a suite of linked tectonic, magmatic, metamorphic, and sedimentologic processes that systematically follow plate interactions, including collision, coupling, and capture resulting in plate reconfiguration and changes of movement. Plate capture, which takes place during mechanical connection of plates within a “clutch” zone, is followed generally by an abrupt transition to plate stretching in response to drag or plate spin. Plate stretch, which is accommodated during drag by a network of complementary strike-slip and normal faults or during spin by regional domains of transtension, is recorded by “postorogenic,” back-arc extension, basin formation, and magmatism, extensive domains of which comprise large igneous provinces. As a captured continental plate is dragged or rotates, ductile mantle is disrupted and displaced by protuberances, such as a slab coupled against the base of an overriding plate and/or orogenic roots extending down from a cratonic core. The mantle turbulence resembles a wave-like ship’s wake with tsunami-like movement, albeit below crust. The arrival of a moving mantle bulge or wave is inferred to be focused along continental plate margins where subduction is induced, as recorded by magmatism and eclogitic rocks that form during deep emplacement of crustal terranes. Concurrent shortening of crust in the vicinity of the plate margin is inferred from inversion and uplift of marginal rift basins, obduction, and development of fold-and-thrust belts. As the mantle wave passes beneath plate interiors, tens to hundreds of meters of uplift, recorded by oceanic atolls, continental stream incision, regional unconformities, and local transitions to evaporite within shelf settings, record epeirogeny. After passage of the wave, common development of sheet-like bodies of quartzose sandstone, especially during the early Paleozoic, suggest postwave, regional subsidence. Resumption and re-invigoration of extension are recorded by eduction of dunked crust and conspicuous, widespread, volcanic eruptions recorded by tuffaceous layers intercalated with carbonaceous black shale within broad basins developed above thickened crust.

The Bretskyan hierarchy, multiscale allopatry, and geobiomes—on the nature of evolutionary things

“…The ecosystem view is even more complex, because it also encompasses abiotic energy and matter transfer, which are tied to geological processes that span many time scales and interact not only horizontally (in geographic space of longitude [λ] and latitude [w] but also in the third dimension [z] across all planetary spheres-crust, mantle, and core). There is no doubt that, at the long time scales of thousands to billions of years, life is an integral part of the Earth's dynamics, with feedbacks working in both directions and most clearly apparent on time scales longer than millions of years (Lovejoy 2015;Wignall 2015;Knoll and Nowak 2017;Spiridonov et al 2017cEichenseer et al 2019;Anderson 2022;Sánchez-Baracaldo et al 2022;Spencer et al 2022;Spiridonov andLovejoy 2022, 2023). Therefore, the hierarchy of ecosystems, and especially the dynamics of their spatial and compositional structure on long time scales, should be understood as a part of the geological/intra-planetary hierarchy of processes and structures.…”