ABSTRACT
This study presents the first detailed description of the upper sedimentary succession of the late Pleistocene and Holocene deposits in the Gulf of San Jorge (Patagonia) based on several ...hundred kilometers of high‐resolution seismic (sparker) profiles and numerous sediment cores. High‐resolution seismic stratigraphy confirms the existence of a paleo‐fluvial network formed during sea‐level lowstands and buried by central basin estuarine deposits during the last marine transgression. Analyses of lithostratigraphy and radiocarbon ages indicate the onset of subtidal sedimentation at ~14 cal ka bp. Before the onset of subtidal conditions, the first steps of marine incursion seem to have led to the development of lagoonal/wind–tidal flat environments, advocating for a sea‐level stillstand. An abrupt increase in the log(Ti/Ca) ratio in a distinct multi‐centimeter‐thick layer and the identification of a wave‐ravinement surface suggest rapid sea‐level rise in the gulf prior to ~14 cal ka bp, consistent with Meltwater Pulse 1A. Overall, this study highlights the significant impact of sea‐level rise on sedimentation in the gulf from the onset of marine incursions to the mid‐Holocene, as well as the reduced contribution, as currently observed, of riverine inputs due to the progressive diminution and withdrawal of glacial drainage starting before the Holocene.
What kind of genetic variation contributes the most to adaptation is a fundamental question in evolutionary biology. By resequencing genomes of 80 individuals, we inferred the origin of genomic ...variants associated with a complex adaptive syndrome involving multiple quantitative traits, namely, adaptation between high and low altitudes, in the vinous-throated parrotbill (Sinosuthora webbiana) in Taiwan. By comparing these variants with those in the Asian mainland population, we revealed standing variation in 24 noncoding genomic regions to be the predominant genetic source of adaptation. Parrotbills at both high and low altitudes exhibited signatures of recent selection, suggesting that not only the front but also the trailing edges of postglacial expanding populations could be subjected to environmental stresses. This study verifies and quantifies the importance of standing variation in adaptation in a cohort of genes, illustrating that the evolutionary potential of a population depends significantly on its preexisting genetic diversity. These findings provide important context for understanding adaptation and conservation of species in the Anthropocene.
The timing of the terminal deglaciation of the Late Paleozoic Ice Age – LPIA in the Paraná Basin has been under investigation. However, the low availability of high-precision radioisotopic ages ...prevents the construction of a detailed chronostratigraphic framework necessary to constrain the demise of the glaciation and perform correlation with contemporaneous records across neighboring basins and within the extensive Paraná Basin. This study aims to contribute to the chronostratigraphic detailing of the Carboniferous-Permian succession of the southern Paraná Basin, interval preserving LPIA glacial-postglacial transition. Therefore, we document new high-precision U-Pb radioisotopic ages and reexamine previously published samples through single crystal chemical abrasion, isotope dilution-thermal ionization mass spectrometry (CA-IDTIMS). We integrate all high-precision radioisotopic ages into the first Bayesian age-depth models for the late Carboniferous-early Permian succession recorded in the southern Paraná Basin. Age-depth models were performed on DU-08-RS and HN-120-RS drill cores, located in the Capané and Candiota paleovalleys, respectively. The weighted mean 206Pb/238U date for the Rio Bonito Formation are 297.914 ± 0.10 (T6), 297.495 ± 0.11 (HN), 296.796 ± 0.114 (T1), 296.293 ± 0.098 (T1.5), 296.252 ± 0.117 (T2), and 296.148 ± 0.136 Ma (RB). For the Itararé Group sample, the weighted mean date is 301.809 ± 0.224 Ma (ITA). T1 and T2 high-precision ages turned out to be older than LA-ICP-MS ages published before (Cagliari et al., 2014), and RB and ITA ages younger (Cagliari et al., 2016). Age-depth models constraints the Rio Bonito Formation between Gzhelian and Sakmarian stages, encompassing ~6.9 and ~1.6 Myr in cores DU-08-RS and HN-120-RS, respectively. The results demonstrate that the successions of the Rio Bonito Formation recorded in Capané and Candiota paleovalleys are contemporaneous. They also corroborate to assign the final glaciation to the early Gzhelian (Late Pennsylvanian) and to place the Carboniferous-Permian boundary within the Rio Bonito Formation, in the study area.
•New high-precision CA-IDTIMS radiometric dating is presented.•The Carboniferous-Permian transition occurs within the Rio Bonito Formation.•Capané and Candiota paleovalleys sedimentary infill are contemporaneous.•Final glaciation in the Paraná Basin likely occurred in the Gzhelian.
In eastern Crete, several normal faults trend both NNE-SSW and E-W. Most of them form impressive bedrock fault scarps indicating ongoing extension in the Hellenic fore-arc. No earthquakes from ...historical and instrumental catalogues can be directly associated with these faults. Geomorphologic profiles across five different faults in sites well-preserved from erosion, deposition or human intervention revealed displacements of ∼6.9 m–∼30 m. Following a robust site selection at the Lastros and Orno faults, we mapped different categories of weathered horizontal ribbons along the bedrock fault plane based on colour contrast, lichen colonisation and karstic features that affect fault plane roughness, features that altogether are interpreted as earthquake horizons. The data indicate coseismic displacements of 15–35 cm for the last three earthquakes at the Lastros fault and 10–20 cm for the last two earthquakes at the Orno fault. To constrain the age of these earthquakes and to estimate millennial fault slip rates, we determined cosmogenic 36Cl concentrations from vertical profiles composed of 24 samples from the exposed Lastros fault plane and 7 samples of the Orno fault plane. Bayesian Markov Chain Monte Carlo (MCMC) modelling implies that the last three earthquakes at the Lastros fault, occurred within the last 1.8 ± 1.2 kyr (EQ1 = 1.1 ± 1.1 kyr, EQ2 = 1.4 ± 1.1 kyr, EQ3 = 1.8 ± 1.2 kyr). Furthermore, Lastros’ slip rate varied with a rate of 0.6 ± 0.3 mm/yr during the last 1.8 ± 1.2 kyr, preceded by a rate of 1.1 ± 0.4 mm/yr from ∼1.8 to 8 kyr; suggesting periods of earthquake clustering. At the Orno fault, the last two earthquakes occurred within the last ∼3.5 kyr accompanied with a slip rate of 0.16+0.06-0.02 mm/yr during postglacial times. This confirms for the first time based on absolute dating, that both NNE-SSW and E-W trending neighbouring faults in Crete were active during the Holocene.
Most of the 13.2 m high Orno fault scarp was exhumed during glacial times, with an apparent slip rate of 0.28+0.12-0.07 mm/yr. The upper part of the Lastros fault scarp (9–12 m) and the apparent age of the four Lastros footwall samples (∼17.9 kyr, ∼26.0 kyr, ∼29.9 kyr, ∼37.4 kyr) underline the long preservation throughout glacial times as well. These findings show that the general hypothesis of predominantly postglacial bedrock fault scarps needs to be regarded with caution at lower latitudes and/or low altitudes (<1000 m), since degradation processes are weaker.
•Cosmogenic dating on postglacial scarps confirms that both NNW-SSE and E-W trending faults were active during the Holocene.•M∼6.4 palaeoearthquakes have a mean recurrence interval of 200–400 yrs on the Lastros and 600–2000 yrs on theOrno fault.•Postglacial slip rate variability of the Lastros fault between ∼0.6 and ∼1.1 mm/yr.•Uppermost free-faces preserved during glacial times, implying weak degradation in lower latitudes and <1000 m altitude.
Abstract
Numerous evolutionary lineages representing an armoured, limno-terrestrial family Echiniscidae are restricted to high mountainous or polar localities, exhibiting clear cold stenothermic ...preferences. One such group is the genus Claxtonia, with its type species Claxtonia wendti, originally described from Svalbard and later on reported globally. In this paper, we re-describe this taxon by establishing the neotype from Spitsbergen. We sequenced five genetic markers (18S rRNA, 28S rRNA, ITS-1, ITS-2, and COI) for multiple populations of Claxtonia, including C. mauccii, C. molluscorum, C. wendti, and several potentially new species, collected in the Alps, Andes, Carpathians, Scotland, Iceland, Southern Appalachians, Spitsbergen, Scandinavian Peninsula, Borneo, and the West Indies. The relationships between these species are elucidated thanks to the phylogenetic reconstructions based on nuclear loci. Various Claxtonia species frequently co-occur in mosses and lichens, which hampers delineating their probable geographic ranges. All historical records of C. wendti are questioned in the light of our revision. Delineation of new species within the genus is nipped in the bud due to numerous problems with original species descriptions, unknown intraspecific (including ontogenetic) variability, and the lack of DNA barcodes. Finally, it is hypothesized that Claxtonia potentially comprises two lineages: a cold-stenothermic one and a thermophilic subtropical–tropical one.
The Eurasian ice sheet complex (EISC) was the third largest ice mass during the Last Glacial Maximum with a span of over 4500 km and responsible for around 20 m of eustatic sea-level lowering. Whilst ...recent terrestrial and marine empirical insights have improved understanding of the chronology, pattern and rates of retreat of this vast ice sheet, a concerted attempt to model the deglaciation of the EISC honouring these new constraints is conspicuously lacking. Here, we apply a first-order, thermomechanical ice sheet model, validated against a diverse suite of empirical data, to investigate the retreat of the EISC after 23 ka BP, directly extending the work of Patton et al. (2016) who modelled the build-up to its maximum extent. Retreat of the ice sheet complex was highly asynchronous, reflecting contrasting regional sensitivities to climate forcing, oceanic influence, and internal dynamics. Most rapid retreat was experienced across the Barents Sea sector after 17.8 ka BP when this marine-based ice sheet disintegrated at a rate of ∼670 gigatonnes per year (Gt a−1) through enhanced calving and interior dynamic thinning, driven by oceanic/atmospheric warming and exacerbated by eustatic sea-level rise. From 14.9 to 12.9 ka BP the EISC lost on average 750 Gt a−1, peaking at rates >3000 Gt a−1, roughly equally partitioned between surface melt and dynamic losses, and potentially contributing up to 2.5 m to global sea-level rise during Meltwater Pulse 1A. Independent glacio-isostatic modelling constrained by an extensive inventory of relative sea-level change corroborates our ice sheet loading history of the Barents Sea sector. Subglacial conditions were predominately temperate during deglaciation, with over 6000 subglacial lakes predicted along with an extensive subglacial drainage network. Moreover, the maximum EISC and its isostatic footprint had a profound impact on the proglacial hydrological network, forming the Fleuve Manche mega-catchment which had an area of ∼2.5 × 106 km2 and drained the present day Vistula, Elbe, Rhine and Thames rivers through the Seine Estuary. During the Bølling/Allerød oscillation after c. 14.6 ka BP, two major proglacial lakes formed in the Baltic and White seas, buffering meltwater pulses from eastern Fennoscandia through to the Younger Dryas when these massive proglacial freshwater lakes flooded into the North Atlantic Ocean. Deglaciation temporarily abated during the Younger Dryas stadial at 12.9 ka BP, when remnant ice across Svalbard, Franz Josef Land, Novaya Zemlya, Fennoscandia and Scotland experienced a short-lived but dynamic re-advance. The final stage of deglaciation converged on present day ice cover around the Scandes mountains and the Barents Sea by 8.7 ka BP, although the phase-lagged isostatic recovery still continues today.
•A new model reconstruction for the EISC deglaciation (23-8 ka BP) is presented.•Ice loading across the High Arctic is tested independently against RSL observations.•The potential locations of >6000 subglacial lakes during the LGM are identified.•The proglacial Fleuve Manche mega-catchment extended >2.5 × 106 km2 across Eurasia.•The EISC contribution to global sea level rise during Meltwater Pulse 1A was ∼2.5 m.
This paper reviews and expands upon stratigraphic and chronologic evidence supporting the interpretation of a strong, early postglacial paleoearthquake in western Quebec-northeastern Ontario, Canada. ...Event horizon mapping at Dasserat, Dufresnoy and Duparquet lakes, Quebec, coring at Chassignolle and Malartic lakes, Quebec, analysis of varve exposures near both the Twin Falls and Frederick House dams, Ontario, and review of published and unpublished logs of varve exposures, reveal that mass transport deposits formed in, or are inferred to have formed in, varve year (vyr) 1483 (relative to the Timiskaming varve series, and about 9.1 ka cal BP) are present at numerous locations within the study area. The spatial extent of the vyr 1483 mass transport deposit signature covers at least 14,600 km2, and is best explained by shaking from a paleoearthquake. The magnitude of the event is estimated to be a minimum of M ∼7.3, which is indicative of a strong paleoearthquake. The vyr 1483 paleoearthquake is one of 11 events of ≥M ∼5, occurring within a 425 varve year period between ∼9.4 and 8.95 ka cal BP, and is likely part of a period of elevated, early postglacial, seismicity associated with rapid crustal unloading. The absence of an equivalent signature within the younger portion of the glaciolacustrine or lacustrine deposits in local lakes, implies that this paleoearthquake is the strongest to occur within the study area since about 9.1 ka cal BP. The highly-precise correlation of widely-spaced mass transport and disturbed deposits provided by varves is essential to the paleoearthquake interpretation.
•Widespread mass transport deposits formed in a common varve year.•Located over at least 14,600 km2 of low seismically active area of Canadian Shield.•Failure signature is best explained by paleoearthquake of minimum magnitude M ∼7.3•Paleoearthquake is likely strongest within study area since about 9.1 ka cal BP.
When and how the extraordinary species diversity in subtropical East Asia formed is intensely debated, and the available evidence is often inconsistent. In this study, we evaluate the effects of pre- ...and post- Quaternary events on the evolutionary and biogeographic history of Chinese beech (Fagus species that now occur in China) to gain new insights into the historical establishment and future fate of the East Asian subtropical forest (EASF). A series of approaches and datasets were used to reconstruct biogeographic and evolutionary history of the Chinese beech. They include phylogeography based on the polymorphisms of the complete chloroplast genomes, species distribution models, and a large palaeobiogeographic dataset including 59 pre-Quaternary fossil records, 296 Quaternary fossil records and 3515 modern pollen records. Our multidisciplinary approach suggests that (i) Chinese beech has dispersed to subtropical East Asia and diversified in the early Miocene when the Asian monsoon (AM) intensified; (ii) the last post-glacial warming resulted in limited poleward displacement but significant contraction at southern and lower elevations; (iii) the poleward dispersal of Chinese beech was limited by drought in the early growing season in temperate China, controlled by the East Asian summer monsoon. Our results support the hypothesis that the establishment of the EASF is closely related to the evolution of the AM. More importantly, we suggest that with continued climate warming (e.g., during the last post-glacial period or under current climate change), the monsoon probably hindered rather than promoted the persistence of deciduous beech species, resulting in a decline in species richness.
•Phylogeography, paleobiogeography and species distribution modelling were integrated.•Asian monsoon (AM) promoted Miocene diversification of East Asian subtropical species.•AM hindered species poleward shift during the post-glacial warming period.•Hygrophilous deciduous species susceptible to mountaintop extinction.
Coastal lagoons are highly productive and biologically diverse landscape features that sustain a range of valuable natural services to societies. Acting as an interface between land and sea, they ...evolve naturally, but are also vulnerable to various forms of human activity. Based on old cartographic material, LiDAR elevation data, Holocene sea level histories, and shoreline modelling, we study the development of coastal lagoons on the postglacially uplifting, tideless coast of the brackish water Baltic Sea. Ecological succession of habitats along the path from bays to semi-enclosed lagoons, coastal lakes or bogs is discussed utilizing community structure analysis of habitat building bottom vegetation. There are about 600 lagoons in Estonia, but they are typically small (bigger ones up to 6 km2) and mostly <1 m deep. Due to ongoing postglacial uplift (1.5−3.4 mm/a), lagoons are just a relatively short (50−500-years long) transitional phase in a long (up to ∼10 000-years) succession. Locating at an altitude of up to 20−30 m, some older, more resilient palaeolagoons can be nowadays distinguished as lakes or bogs, while smaller ones have blended into the surrounding landscape. The contemporary lagoons are ephemeral too, because the emerging terrain has already been flattened by erosion and sedimentation. After separation from the sea, the brackish water habitat is gradually replaced with freshwater habitat and both biodiversity and plants coverage usually increases. As organic deposits build up, low-growth shores are replaced with high-growth vegetation; reedbeds expand. Detached from their marine past, communities typical for lakes, fens, bogs or forests are finally formed. As a result of eutrophication, ongoing climate change and sea level rise, the balance between emergence of new lagoons and their disappearance due to distancing and swamping has shifted over the past 100 years.
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•Postglacial uplift is the main shaper of lagoons; barrier formation the secondary.•“Coastal lagoon” is a relatively brief phase in a long succession path.•Successional changes in habitat forming bottom vegetation are studied with ANOSIM.•Uplift driven distancing and overgrowing directs: bay – lagoon – lake – bog.•Many inland lakes and bogs up to 20–30 m altitude are palaeolagoons in Estonia.
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► Mainland China and adjacent areas harbor the world’s most diverse temperate flora. ► We review the phylogeographic literature on this flora for the first time. ► Studies generally ...reveal strong genetic imprints of Quaternary climate and environmental change. ► This challenges the oft-stated view of East Asia as a glacial sanctuary for temperate plants.
The Sino-Japanese Floristic Region (SJFR) of East Asia harbors the most diverse of the world’s temperate flora, and was the most important glacial refuge for its Tertiary representatives (‘relics’) throughout Quaternary ice-age cycles. A steadily increasing number of phylogeographic studies in the SJFR of mainland China and adjacent areas, including the Qinghai–Tibetan-Plateau (QTP) and Sino-Himalayan region, have documented the population histories of temperate plant species in these regions. Here we review this current literature that challenges the oft-stated view of the SJFR as a glacial sanctuary for temperate plants, instead revealing profound effects of Quaternary changes in climate, topography, and/or sea level on the current genetic structure of such organisms. There are three recurrent phylogeographic scenarios identified by different case studies that broadly agree with longstanding biogeographic or palaeo-ecological hypotheses: (i) postglacial re-colonization of the QTP from (south-)eastern glacial refugia; (ii) population isolation and endemic species formation in Southwest China due to tectonic shifts and river course dynamics; and (iii) long-term isolation and species survival in multiple localized refugia of (warm-)temperate deciduous forest habitats in subtropical (Central/East/South) China. However, in four additional instances, phylogeographic findings seem to conflict with a priori predictions raised by palaeo-data, suggesting instead: (iv) glacial in situ survival of some hardy alpine herbs and forest trees on the QTP platform itself; (v) long-term refugial isolation of (warm-)temperate evergreen taxa in subtropical China; (vi) ‘cryptic’ glacial survival of (cool-)temperate deciduous forest trees in North China; and (vii) unexpectedly deep (Late Tertiary/early-to-mid Pleistocene) allopatric-vicariant differentiation of disjunct lineages in the East China-Japan-Korea region due to past sea transgressions. We discuss these and other consequences of the main phylogeographic findings in light of palaeo-environmental evidence, emphasize notable gaps in our knowledge, and outline future research prospects for disentangling the evolution and biogeographic history of the region’s extremely diverse temperate flora.
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