Abstract : The heterogeneous continental lithosphere of Western Europe inherits billion of years of tectonic evolution, mineral transformation and magmatic addition. Its deformation over broad regions form collisional orogens and large forelands basins, which tectonic evolution is controlled by the interactions between its inherited properties, large-scale plate convection and smaller-scale plate subduction. How these first-order interactions are connected through time and space to control collision evolution is however largely unknown. Here we explore the evolution of the Alpine collision along a transect stretching between northern Africa and Europe. We show that the complex patterns of Alpine deformation from the Rif-Betic, Pyrenean collision and Europe primarily reflects continental fragmentation and drastic weakening of the lithosphere that occurred during the Late Permian-Triassic. Subsequent rifting episodes from Jurassic to Early Cretaceous left imprints on the thermal evolution of sedimentary basins, together with significant increase of Iberia topography, asthenospheric flow, and plate-scale dispersion of terrigenous sediments. The lack of large oceanic domain, at the transition between Atlantic and western Tethys, resulted in the distributed of shortening over a broad region from north Africa, Iberia and Europe, in the upper Cretaceous (~70 Ma). Detailed contraints on the sequence of shortening throughout West Europe from Late Cretaceous to the Tortonian reveals that the overall evolution of the west-alpine orogenic domain is primarily controlled by the nature and architecture of the continental lithosphere but became progressively controlled by sub-lithospheric processes associated with late/post-orogenic tectonic evolution.
Taiwan is an archetypal example of continental accretionary wedges. Yet the generally poor knowledge of three-dimensional strain distribution over time and role of architecture of the rifted margin shed doubt on the cylindrical two-dimensional kinematic models of Taiwan collision. Here we provide new field-based constraints on strain distribution, new Raman Spectroscopy on Carbonaceous Materials temperatures and apply mica-chlorite multiequilibrium approach to determine pressure-temperature in the Central Range of Taiwan. We identify three distinct structural domains that define zones of orthogonal shortening in the western Backbone Range and left-lateral ductile shearing overprinted by left-lateral transtensional brittle deformation in eastern Central Range. Field surveys show the lack of nappe stacking in the Backbone Range. Combining new temperature estimates with existing thermochronological constraints we emphasize that western Taiwan mostly inherited preorogenic thermal history. We show that metamorphic peak conditions of 5-6 kbar and 330-400 degrees C in the eastern Backbone Range and HP rocks of the Yuli Belt exhumed along the P-T paths related to transcurrent deformation. We propose a three-dimensional kinematic model of Taiwan accounting for the oblique motion of the Philippine Sea Plate relative to the plate boundary and the reactivation of a NS striking transform fault in the South China Sea rifted margin. Recent and ongoing strain partitioning in the Taiwan accretionary wedge is reflected by the coexistence of brittle left-lateral shear, oblique extension, and contraction. Our results have impact on orogen-based plate kinematic reconstructions that consider two-dimensional kinematic evolution of orogens. Key Points Strain distribution in south central Taiwan reveals partitioning between orthogonal contraction and left-lateral shear Dome-like architecture and exhumation of high-grade rocks in eastern Taiwan are best explained by transcurrent deformation Oblique convergence and rift architecture accounts for the 3-D strain distribution in Taiwan
The Betic‐Rif orogen is a key region to understand the evolution of the plate boundary between Africa and Iberia/Europe. This study focuses on the Flysch Complex, which is considered the sedimentary cover of a domain originally positioned between the Iberian and Alboran margins. Based on stratigraphic and depositional evolution constraints, evidence for salt tectonics, combined with new apatite fission‐tracks (AFT) and (U‐Th‐Sm)/He ages from the Flysch Complex and the Subbetic Zone, we propose a geodynamic interpretation for the formation of the Betic Cordillera, accounting for moderate N‐directed transport of the Flysch Complex and synchronous exhumation between External and Internal Zones of the Betic. Early contraction between Africa and Iberia/Europe is reflected in the Cretaceous Flysch basin by a prolonged period of residence in the partial annealing zone for AFT and onset of foreland subsidence at 50 Ma. This stage lasted until the Early to Middle Miocene (20–15 Ma), marked by the rapid succession, in less than 5 Ma, of the deposition of Cenozoic flysch and their rapid exhumation. This event is interpreted to reflect the W‐directed retreating mantle delamination between Africa and Iberia margins at the origin of the collapse of the proto‐Betic orogenic domain and formation of the Alboran domain.
The impact of rift-related processes on tectonic and thermal evolution of collisional orogens is poorly documented. Here, we study the northern Pyrenees, a region that has preserved a geological record of the transition from rifting to collision. Using modeling of new low-temperature thermochronological data, including fission track and (U-Th)/He on apatite and zircon, we propose a temporal reconstruction of the inversion of the European rifted margin. Our data confirm that rifting and related cooling started in the Late Paleozoic-Triassic. Throughout the Jurassic and Early Cretaceous the European margin recorded slow heating during postrift subdsidence. Modeling of thermochronological data allows distinguishing subsidence and denudation controlled by south dipping normal faults in granitic massifs that reflect a second episode of crustal thinning at 130-110Ma. Following onset of convergence at 83Ma, shortening accumulated into the weak and hot Albian-Cenomanian rift basins floored by both hyperextended continental crust and exhumed subcontinental mantle. The lack of cooling during this initial stage of convergence is explained by the persistence of a high geothermal gradient. The onset of exhumation-related cooling is recognized in the whole Pyrenean region at 50-35Ma. This timing reveals that the main phase of mountain building started when hyperextended rift basins closed and collision between proximal domains of the rifted margin occurred.