A critical reappraisal of paleomagnetic evidence for Philippine Sea Plate rotation

SHAvdL and DJJvH were funded by NWO Vici grant 865.17.001 to DJJvH. DPG is funded by a ‘Ramón y Cajal’ Fellowship (RYC2019-028244-I) and the grant KiTSuNE (PID2021-128801NA-I00) both funded by ‘ MCIN/AEI/ESF Investing in your future’. We thank Fagan Matthys and CJ Paulino for their help in the field.The kinematic history of the Philippine Sea Plate (PSP) is crucial for interpreting its geological record related to subduction initiation processes and the paleogeography of the junction between the Paleo-Pacific and Tethyan oceanic realms. However, reconstructing PSP's kinematic history is difficult because the plate has been surrounded by subduction zones for most of its history. In absence of marine magnetic anomalies to constrain PSP's motion relative to its neighboring plates, paleomagnetic data may be used as quantitative constraints on its motion. Previous paleomagnetic studies interpreted easterly deflected declinations to infer clockwise rotations of up to 90° since the Eocene. However, rotations inferred from these datasets may also reflect local block rotations related to plate margin deformation. We here re-evaluate to what extent paleomagnetic data from the PSP unequivocally demonstrate plate motion rather than local rotation. To this end, we provide new data from Guam, in the Mariana forearc, and reassess published paleomagnetic data. Our new data from Guam come from two localities in the Eocene, two in the Oligocene, and two in the Miocene. Our compilation assesses data quality against recently defined criteria. Our new results demonstrate that in Guam, declination differences of up to 35° exist in rocks of Eocene age, indicating local rotations. Our compilation identifies both clockwise and counterclockwise rotations from the plate margins, with little confidence which of these would reflect plate-wide rotation. We compiled paleolatitude data from igneous rocks, which we correct for microplate rotation constrained by intra-PSP marine magnetic anomalies and show a northward drift of the PSP of ∼15° since the Eocene, but without a paleomagnetic necessity for major vertical axis rotation. Hence, with the currently available data, rotations of the PSP may be permitted, but are not required. Plate motion is currently better reconstructed from geological constraints contained in circum-PSP orogenic belts.Nederlandse Organisatie voor Wetenschappelijk Onderzoek 865.17.001‘Ramón y Cajal’ Fellowship RYC2019-028244-IKiTSuNE (PID2021-128801NA-I00)MCIN/AEI/ESF Investing in your futur

Tectonic evolution of NW Iberia during the Paleozoic inferred from the geochemical record of detrital rocks in the Cantabrian Zone

The Cantabrian Zone of NWIberia preserves a voluminous, almost continuous, sedimentary sequence that ranges in age from Ediacaran to Early Permian. Its tectonic setting is controversial and recent hypotheses include (i) passive margin deposition along the northern margin of Gondwana, (ii) an active continental margin, or (iii) the margin of a drifting ribbon continent and (iv) a combination of the three aforementioned possibilities. In this paperwe present geochemical data from 21 samples taken in detrital rocks in the Cantabrian Zone from Ediacaran to Early Permian age. The results, together with previously published detrital zircon ages from these strata, allow a comprehensive analysis of changing tectonic scenarios and provenance through time. Collectively, these data indicate that this portion of Iberia was an active margin during the Ediacaran that evolved to become part of the passive margin of Gondwana at least from Ordovician to Late Devonian times. Changes in geochemistry, zircon age distribution and Sm/Nd isotopes during the Carboniferous are attributed to the far-field effects of the onset of the collision between Gondwana and Laurussia, and related processes such as recycling of older sedimentary sequences, as well as the involvement of the rocks formed during the Variscan orogeny and oroclinal buckling. Latest Carboniferous and Permian show a more juvenile Sm/Nd and higher values of illite cristallinity that may support the hypothesis of lithospheric foundering after oroclinal buckling

Provenance analysis of the Paleozoic sequences of the northern Gondwana margin in NW Iberia: Passive margin to Variscan collision and orocline development

The Cantabrian Zone of NW Iberia preserves a voluminous, almost continuous, sedimentary sequence that ranges from Neoproterozoic to Early Permian in age. Its tectonic setting is controversial and recent hypotheses include (i) passive margin deposition along the northern margin of Gondwana or (ii) an active continental margin or (iii) a drifting ribbon continent. In this paper we present detrital zircon U–Pb laser ablation age data from 13 samples taken in detrital rocks from the Cantabrian Zone sequence ranging from Early Silurian to Early Permian in depositional age. The obtained results, together with previously published detrital zircon ages from Ediacaran– Ordovician strata, allow a comprehensive analysis of changing provenance through time. Collectively, these data indicate that this portion of Iberia was part of the passive margin of Gondwana at least from Ordovician to Late Devonian times. Zircon populations in all samples show strong similarities with the Sahara Craton and with zircons found in Libya, suggesting that NW Iberia occupied a paleoposition close to those regions of present-day northern Africa during this time interval. Changes in provenance in the Late Devonian are attributed to the onset of the collision between Gondwana and Laurussia. Additionally, the Middle Carboniferous to Permian samples record populations consistent with the recycling of older sedimentary sequences and exhumation of the igneous rocks formed before and during the Variscan orogeny. Late-Devonian to Permian samples yield zircon populations that reflect topographic changes produced during the Variscan orogeny and development of the lithospheric scale oroclinal buckling

Iberian late-Variscan granitoids: Some considerations on crustal sources and the significance of “mantle extraction ages

A suite of post-tectonic granitoids (mostly peraluminous, broadly I-type granodiorites and monzogranites) and mafic rocks from NWIberia with crystallization ages between ca. 309 and 290 Ma has been investigated for Sm–Nd isotopes and inherited zircon content in order to constrain the nature of their source rocks. εNd values (at 300 Ma) vary from −0.2 to −5.9 and TDM values range from 1.01 to 1.58 Ga. Inherited (xenocrystic) zircons yielded ages ranging from 458 to 676 Ma, with 90% of data between 490 and 646 Ma, corresponding to Neoproterozoic(mostly Ediacaran), Cambrian andOrdovician ages. Only three highlydiscordant analyses yielded ages older than 650 Ma. Based on the data reported herein and relevant data fromthe literaturewe contend that post-tectonic granitoids of the Iberian Variscan Belt (with exception of the scarce anatectic S-type granitoids) were derived mostly from metaigneous lower crustal sources which in turn were ultimately derived from a subcontinental lithospheric mantle enriched between ca. 0.9 and 1.1 Ga. I-type granitoids and mantle-derived mafic rocks both underwent varying degrees of contamination by ametasedimentary lower crust depleted in pre-650 Ma zircon (through previousmelting episodes) with a time-integrated Sm–Nd evolution different to that of the metaigneous lower crust. Participation of this metasedimentary crust in the genesis of these granitoids may account for Nd isotopic variability and Nd model ages well in excess of 1.2 Ga

Whence come detrital zircons in Siluro-Devonian rocks from Iberia?

Seven Silurian and Devonian samples from the Cantabrian and Central Iberian zones of the Variscan belt have been investigated for paleogeographic purposes using detrital zircon U-Pb ages. A total of 764 analyses were performed. All samples contain four main age populations in variable relative proportions: Ediacaran–Cryogenian (ca. 0.55–0.8 Ga), Tonian–Stenian (0.85–1.2 Ga), Paleoproterozoic (ca. 1.8–2.2 Ga) and Archean (ca. 2.5–3.3 Ga). The two first groups constitute ca. 60–80% of the total population in all samples. In addition, 5 samples contain very minor Paleozoic (Cambrian) zircons and 6 samples contain minor but significant zircons of Middle and Early Mesoproterozoic age (Ectasian–Calymmian). These data, used in conjunction with detrital zircon U-Pb data of underlying Ordovician and Ediacaran strata constrain the evolution of the northern margin of west Gondwana, highlighting the transition from an arc environment (Cadomian-Avalonian arc orogeny) to a stable platform following the opening of the Rheic Ocean and the drift of Avalonian terranes. Variations in detrital zircon populations in Middle–Late Devonian times reflect the onset of Variscan convergence between Laurussia and Gondwana. The abundance (up to ca. 50%) of zircons of Tonian–Stenian age in Devonian sedimentary rocks, that could not have been recycled from the underlying strata, may be interpreted in different ways: a) the existence of a large Tonian–Stenian arc terrane exposed in the NE African realm (in or around the Arabian-Nubian shield) that was progressively exhumed throughout the Paleozoic, b) the participation from Ordovician times onwards of a more easterly alongshore provenance of Tonian–Stenian zircons. In this scenario, the South China block could have furnished Tonian– Stenian zircons to the Ordovician and Siluro-Devonian basins of Iberia, c) increase in the relative proportion of Tonian–Stenian zircons with respect to the Ediacaran– Cryogenian population (arc-derived zircons) due to the drift of the Avalonian-Cadomian ribbon continent following the opening of the Rheic Ocean.Peer Reviewe

Buckling an orogen: The Cantabrian Orocline

The Paleozoic Variscan orogeny was a large-scale collisional event that involved amalgamation of multiple continents and micro-continents. Available structural, geological, geochemical, and geophysical data from Iberia are consistent with a model of oroclinal bending at the lithospheric scale of an originally near-linear convergent margin during the last stages of Variscan deformation in the late Paleozoic. Closure of the Rheic Ocean resulted in E-W shortening (in present-day coordinates) in the Carboniferous, producing a near linear N-S–trending, east-verging orogenic belt. Subsequent N-S shortening near the Carboniferous-Permian boundary resulted in oroclinal bending, highlighted by the formation of the Cantabrian Orocline. Together, these data constrain oroclinal bending in Iberia to have occurred during the latest Carboniferous over about a 10-million-year time window, which agrees well with recent geodynamical models and structural data that relate oroclinal bending with lithospheric delamination in the Variscan. This late-stage orogenic event remains an enigmatic part of final Pangaea amalgamation

A critical reappraisal of paleomagnetic evidence for Philippine Sea Plate rotation

The kinematic history of the Philippine Sea Plate (PSP) is crucial for interpreting its geological record related to subduction initiation processes and the paleogeography of the junction between the Paleo-Pacific and Tethyan oceanic realms. However, reconstructing PSP's kinematic history is difficult because the plate has been surrounded by subduction zones for most of its history. In absence of marine magnetic anomalies to constrain PSP's motion relative to its neighboring plates, paleomagnetic data may be used as quantitative constraints on its motion. Previous paleomagnetic studies interpreted easterly deflected declinations to infer clockwise rotations of up to 90° since the Eocene. However, rotations inferred from these datasets may also reflect local block rotations related to plate margin deformation. We here re-evaluate to what extent paleomagnetic data from the PSP unequivocally demonstrate plate motion rather than local rotation. To this end, we provide new data from Guam, in the Mariana forearc, and reassess published paleomagnetic data. Our new data from Guam come from two localities in the Eocene, two in the Oligocene, and two in the Miocene. Our compilation assesses data quality against recently defined criteria. Our new results demonstrate that in Guam, declination differences of up to 35° exist in rocks of Eocene age, indicating local rotations. Our compilation identifies both clockwise and counterclockwise rotations from the plate margins, with little confidence which of these would reflect plate-wide rotation. We compiled paleolatitude data from igneous rocks, which we correct for microplate rotation constrained by intra-PSP marine magnetic anomalies and show a northward drift of the PSP of ∼15° since the Eocene, but without a paleomagnetic necessity for major vertical axis rotation. Hence, with the currently available data, rotations of the PSP may be permitted, but are not required. Plate motion is currently better reconstructed from geological constraints contained in circum-PSP orogenic belts

Cumulative Genetic Score and C9orf72 Repeat Status Independently Contribute to Amyotrophic Lateral Sclerosis Risk in 2 Case-Control Studies

[Background and Objectives] Most patients with amyotrophic lateral sclerosis (ALS) lack a monogenic mutation. This study evaluates ALS cumulative genetic risk in an independent Michigan and Spanish replication cohort using polygenic scores.[Methods] Participant samples from University of Michigan were genotyped and assayed for the chromosome 9 open reading frame 72 hexanucleotide expansion. Final cohort size was 219 ALS and 223 healthy controls after genotyping and participant filtering. Polygenic scores excluding the C9 region were generated using an independent ALS genome-wide association study (20,806 cases, 59,804 controls). Adjusted logistic regression and receiver operating characteristic curves evaluated the association and classification between polygenic scores and ALS status, respectively. Population attributable fractions and pathway analyses were conducted. An independent Spanish study sample (548 cases, 2,756 controls) was used for replication.[Results] Polygenic scores constructed from 275 single-nucleotide variation (SNV) had the best model fit in the Michigan cohort. An SD increase in ALS polygenic score associated with 1.28 (95% CI 1.04–1.57) times higher odds of ALS with area under the curve of 0.663 vs a model without the ALS polygenic score (p value = 1 × 10−6). The population attributable fraction of the highest 20th percentile of ALS polygenic scores, relative to the lowest 80th percentile, was 4.1% of ALS cases. Genes annotated to this polygenic score enriched for important ALS pathomechanisms. Meta-analysis with the Spanish study, using a harmonized 132 single nucleotide variation polygenic score, yielded similar logistic regression findings (odds ratio: 1.13, 95% CI 1.04–1.23).[Discussion] ALS polygenic scores can account for cumulative genetic risk in populations and reflect disease-relevant pathways. If further validated, this polygenic score will inform future ALS risk models.National ALS Registry/CDC/ATSDR (1R01TS000289); National ALS Registry/CDC/ATSDR CDCP-DHHS-US (CDC/ATSDR 200-2013-56856); NIEHS K23ES027221; NIEHS R01ES030049; NINDS R01NS127188, ALS Association (20-IIA-532), the Dr. Randall W. Whitcomb Fund for ALS Genetics, the Peter R. Clark Fund for ALS Research, the Scott L. Pranger ALS Clinic Fund, and the NeuroNetwork for Emerging Therapies at the University of Michigan. This work was supported in part by the Intramural Research Program of the NIH, National Institute on Aging (Z01-AG000949-02). Project “ALS Genetic study in Madrid Autonomous Community” funded by “ESTRATEGIAS FRENTE A ENFERMEDADES NEURODEGENERATIVAS” from Spanish Ministry of Health.Peer reviewe

Çédille, revista de estudios franceses

Presentació