Allochthonous salt advance recorded by the adjacent syn-kinematic sedimentation: Example from the Les Avellanes diapir (South Central Pyrenees)

This work aims to present the Les Avellanes diapir as a field analog to inquire how the origin, advance, and emplacement of an allochthonous salt body in continental settings influence the local sedimentation in terms of facies distribution, sediment provenance, and stratigraphic relationships. At the frontal part of the South-Central Pyrenean fold-and-thrust belt (Spain), the Les Avellanes diapir is an outcropping salt structure made of Triassic evaporites, lutites and carbonates. At the diapir's western boundary, a structurally controlled sub-basin presents a well-preserved, early Oligocene in age, mixed clastic-evaporitic sedimentary sequence which recorded the lateral extrusion of the diapir and its emplacement as an allochthonous salt sheet. To define the events and processes recorded by the adjacent sedimentary sequences, and to unravel the diapir evolution and the nature of the diapir contact at the study area, we have combined sedimentary, petrologic, and stratigraphic data. Three stratigraphic sections have been built, from which 8 lithostratigraphic facies associations have been described, interpreted, and correlated across the sub-basin. The deformation within the diapir deposit is also described and interpreted together with the sedimentary rocks. A prograding alluvial to colluvial system is associated with the piercing of the salt, which was exposed at the surface towards the NE area of the sub-basin. The dissolution of the salt resulting in the formation of a caprock with stacks of stringers of intrasalt carbonates and dolerites layers. The ongoing uplifting at the NE caused the incision of the local drainage network, marked as a paleo-relief in the stratigraphic sequence, filled by syn-kinematic breccias derived by the erosion, transport, and sedimentation of the caprock. The headward erosion reached the salt underneath the caprock, triggering the lateral extrusion. Thus, salt flowed southwards, favored by the local topography, overriding the syn-kinematic breccia deposit. Foliation and other shear-related deformation structures are observed in a megabreccia made of caprock remnants which overlap the sedimentary, syn-kinematic breccias along the base of the salt sheet deposit. These structures were probably formed during the advance of the salt sheet. The data acquired and interpreted in this work allows for the conceptualization of the relative lateral movement of a salt sheet front as recorded by adjacent syn-kinematic sedimentation in continental settings. Salt supply and erosion rates are compared with topographic slope, sedimentation, and salt dissolution as major controlling parameters of the salt sheet advance. The resulting combinations are expressed by the progradation, aggradation, and retrogradation in terms of proximal over distal facies

Salt sheet extrusion and emplacement within the South-Central Pyrenean fold-and-thrust belt: the Les Avellanes Diapir case-of-study

A detailed geological map of the Les Avellanes salt Diapir (South-Central Pyrenees, Spain) that includes both the diapir body and adjacent areas is presented to understand the diapir evolution and geometry. Structural, stratigraphical, and sedimentary data north and south of the diapir is used to infer the timing of its emplacement. The northern diapir boundary is characterized by a set of extensional faults oblique to the main Pyrenean trend, while the southern boundary is an extrusive salt sheet that overlays the late Eocene-early Oligocene sequence in three adjacent sub-basins. Salt extrusion occurred due to synorogenic folding.The topography created as salt extruded trapped the arrival of external sediments from the north, blocking the transport pathways southward. Low sedimentation rates southwards allowed for the lateral salt extrusion, advancing southwards from the feeder. The salt sheet emplacement was postdated by Oligocene conglomerates, indicating that the salt extrusion was a relatively quick event.</p

Salt sheet extrusion and emplacement within the South-Central Pyrenean fold-and-thrust belt: the Les Avellanes Diapir case-of-study

ABSTRACTA detailed geological map of the Les Avellanes salt Diapir (South-Central Pyrenees, Spain) that includes both the diapir body and adjacent areas is presented to understand the diapir evolution and geometry. Structural, stratigraphical, and sedimentary data north and south of the diapir is used to infer the timing of its emplacement. The northern diapir boundary is characterized by a set of extensional faults oblique to the main Pyrenean trend, while the southern boundary is an extrusive salt sheet that overlays the late Eocene-early Oligocene sequence in three adjacent sub-basins. Salt extrusion occurred due to synorogenic folding. The topography created as salt extruded trapped the arrival of external sediments from the north, blocking the transport pathways southward. Low sedimentation rates southwards allowed for the lateral salt extrusion, advancing southwards from the feeder. The salt sheet emplacement was postdated by Oligocene conglomerates, indicating that the salt extrusion was a relatively quick event

The Kinematics of a salt sheet recorded in an array of discorted intrasalt stringers (Les Avellanes Diapir - Sputh-Central Pyrenees)

Stringers represent fragments of competent, brittle layers, formerly interstratified within a layered evaporitesequence (LES) that are entrained and deformed by viscous flow. To resolve the impact of the stringers on thedeformation style of an extrusive salt sheet, an array of decameter-thick, carbonate stringers, preserved in thecaprock matrix of the Les Avellanes Diapir (South-Central Pyrenees) was analysed. The diapir exposure wasmapped in detail to produce a cross-section that shows the stringer assemblage. To understand the dynamicbehaviour of stringers, this natural prototype has been reproduced using scaled analogue models. In the model,stringers were carried into the salt sheet, rotating and deforming while migrating toward the sheet front. Thearray of stringers can be divided into the following three structural domains: 1) a feeder domain mainly hostingvertical stringers parallel to the stem wall that rotate to a subhorizontal orientation as they approach theallochthonous sheet, 2) a sheet domain containing stack-like sets of subvertical and overturned, to subhorizontalstringers, as well as isoclinally and recumbently folded stringers, and 3) a sheet front domain characterised bystringers dipping toward the salt sheet front. Compartmentalization of the horizontal flow by the transportedstringers controlled the deformation in the caprock matrix above. Finally, the similarity between the field observationsand the model is evaluated and discussed to shed light on the Les Avellanes Diapir kinematic evolution.</p

The genome sequencing of an albino Western lowland gorilla reveals inbreeding in the wild

Altres ajuts: ERC grant: ERC-2010-StG_20091118. The Andalusian Government for grants CSD2007-00008 and CVI-3488, supported by FEDER to JLG-S The Barcelona Zoo (Ajuntament de Barcelona) for an award to JP-M. EEE is an investigator with the Howard Hughes Medical InstituteBackground: the only known albino gorilla, named Snowflake, was a male wild born individual from Equatorial Guinea who lived at the Barcelona Zoo for almost 40 years. He was diagnosed with non-syndromic oculocutaneous albinism, i.e. white hair, light eyes, pink skin, photophobia and reduced visual acuity. Despite previous efforts to explain the genetic cause, this is still unknown. Here, we study the genetic cause of his albinism and making use of whole genome sequencing data we find a higher inbreeding coefficient compared to other gorillas.- Results: we successfully identified the causal genetic variant for Snowflake's albinism, a non-synonymous single nucleotide variant located in a transmembrane region of SLC45A2. This transporter is known to be involved in oculocutaneous albinism type 4 (OCA4) in humans. We provide experimental evidence that shows that this amino acid replacement alters the membrane spanning capability of this transmembrane region. Finally, we provide a comprehensive study of genome-wide patterns of autozygogosity revealing that Snowflake's parents were related, being this the first report of inbreeding in a wild born Western lowland gorilla.- Conclusions: in this study we demonstrate how the use of whole genome sequencing can be extended to link genotype and phenotype in non-model organisms and it can be a powerful tool in conservation genetics (e.g., inbreeding and genetic diversity) with the expected decrease in sequencing cos