Glacial History Research Articles

Modeling of the Late Quaternary Glacial History of the La Ji Shan: Implications for the Global Last Glacial Maximum on the Northeastern Tibetan Plateau

Modeling of the Late Quaternary Glacial History of the La Ji Shan: Implications for the Global Last Glacial Maximum on the Northeastern Tibetan Plateau

How a New Cenozoic Geology and Glacial History Paradigm Explains Arkansas-Red River Drainage Divide Area Topographic Map Evidence in and near Pontotoc County, Oklahoma, USA

A new Cenozoic geology and glacial history paradigm (new paradigm), fundamentally different from the accepted Cenozoic geology and glacial history paradigm (accepted paradigm), describes a thick North American continental icesheet (located where continental icesheets are usually reported to have been) which by deep erosion and uplift of surrounding regions created and occupied a deep “hole” (the accepted paradigm does not see this thick ice sheet or the deep “hole”). Unusual erosional landform features in the southeast Oklahoma Pontotoc County region including the asymmetric Canadian-Red River drainage divide, a large escarpment-surrounded basin in which most south-oriented Clear Boggy Creek headwaters begin, and a large escarpment-surrounded upland on which the south-oriented Blue River begins, are used to test the new paradigm’s ability to use large and prolonged south-oriented melt water floods to explain previously unexplained or poorly explained detailed topographic map drainage system and erosional landform evidence. Numerous low points (referred to as divide crossings) indicate large and prolonged south-oriented melt water floods did flow across what is now the Canadian-Red River drainage divide (an interpretation also consistent with Clear Boggy Creek escarpment-surrounded basin and Blue River escarpment-surrounded upland shapes). The new paradigm described massive and prolonged melt water floods also account for previously unrecognized deep regional erosion (which is determinable from detailed topographic map evidence). East-oriented Canadian River valley headward erosion (from the Arkansas River valley) diverted the long-lived south-oriented meltwater floods to the Arkansas River valley and to what ultimately became the deep “hole’s” only southern exit. Previous southeast Oklahoma drainage history interpretations (made from the accepted paradigm perspective in which Rocky Mountain glacier melt water flowed to east-oriented rivers) do not provide adequate water volumes or flow directions to explain the detailed topographic map drainage system and erosional landform evidence, which the new paradigm’s massive and prolonged south-oriented melt water floods do explain.

Detecting the phylogenetic signal of glacial refugia in a bryodiversity hotspot outside the tropics

AbstractIntroductionGlacial refugia have likely been important in shaping diversity gradients outside the tropics. Many taxa that have high extratropical diversity in the present day, such as mosses, may have persisted in glacial refugia. However, the biogeographical histories of most species within refugia remain unclear.LocationHaida Gwaii archipelago, north‐west coast of British Columbia, Canada.TaxaBryophyta (mosses).MethodsWe reconstructed the regional phylogeny of the mosses of Haida Gwaii, a putative glacial refugium and ‘hotspot’ of moss diversity, and used phylogenetic comparative methods to examine the macroecological imprint of glacial refugia on the geographic range structure and phylogenetic attributes of present‐day moss assemblages.ResultsWe found that many mosses have widespread, but disjunct, distributions, with few close relatives on the islands. We suggest that these features reflect the imprint of glacial history, whereby species within refugia represent isolated populations of previously more widespread species that may have diversified elsewhere. We also observed evidence for phylogenetic overdispersion of species within high‐elevation habitats, which best match the climatic regime of the historical glacial refugium. Our results are consistent with the filtering of evolutionarily distinct glacial relicts within these habitats, which contrasts markedly with the patterns of phylogenetic clustering observed across other non‐refugial habitat types.Main conclusionsThe islands of Haida Gwaii represent an extratropical hotspot of bryophyte diversity. Our study illustrates how the present‐day phylogenetic structure of mosses on Haida Gwaii may have been shaped by glacial history, and highlights the importance of glacial refugia in maintaining extratropical moss diversity.

Oceanographic and climatic influences on Trooz Glacier, Antarctica during the Holocene

To evaluate the significance of recent widespread glacial recession in the Antarctic Peninsula, it is imperative to extend the limited instrumented record of glacier change with long sedimentary archives of the Holocene. Reconstructing glacial histories that capture the variability of environments in the Antarctic Peninsula will enable better constraint of ocean and climate forcings on regional glacial stability. Two sediment cores are analyzed from the 2007 RV/IB N.B. Palmer cruise to Collins Bay, the embayment immediately offshore Trooz Glacier on the Graham Land coast, and provide an archive to test controls on long-term stability of outlet glaciers in an open bay setting. Radiocarbon and Lead-210 (a short-lived radioisotope) age-depth models provide a timeline for Trooz Glacier behavior and associated oceanographic changes over the last 10,000 years.Magnetic susceptibility, grain size, diatom assemblage, total organic carbon, nitrogen, and stable isotopes of organic carbon are utilized as proxies for changing glacial and ocean conditions. Outer Collins Bay deglaciated by ∼10000 cal yr B.P. Diatom abundance and organic content signal productivity increase during further glacial recession from ∼8900 to 6100 cal yr B.P., which coincided with upwelling of relatively warm Circumpolar Deep Water into the bay. High productivity, characterized by Thalassiosira antarctica-dominated diatom assemblages with prominence of Fragilariopsis kerguelensis, indicate open marine conditions with incursion of offshore currents into the bay from ∼6100 to 760 cal yr B.P. A sharp decrease in organic content, diatom abundance, and grain size indicate more sea ice and ice-tongue/ice-canopy advance from ∼760 to 240 cal yr B.P., when the floating ice canopy in outer Collins Bay retreated to near its present-day position and productivity increased. During the period of the 1950's to 1990's, Trooz Glacier was one of only two Antarctic Peninsula glaciers that advanced slightly. Over the Holocene, oceanographic forcing dominated the long-term stability of Trooz Glacier due to its open aspect, and it is unknown how Trooz Glacier will respond to continued influence of Circumpolar Deep Water in the future. Understanding ocean forcings on glacial stability, together with other local controls like drainage basin configuration and bay geometry, should help contextualize the modern retreat and improve prediction of glacial response to prevalent Circumpolar Deep Water circulation in this dynamic region.

Plecoptera (Insecta) Diversity in Indiana: A Watershed-Based Analysis

Plecoptera, an environmentally sensitive order of aquatic insects commonly used in water quality monitoring is experiencing decline across the globe. This study addresses the landscape factors that impact the species richness of stoneflies using the US Geological Survey Hierarchical Unit Code 8 drainage scale (HUC8) in the state of Indiana. Over 6300 specimen records from regional museums, literature, and recent efforts were assigned to HUC8 drainages. A total of 93 species were recorded from the state. The three richest of 38 HUC8s were the Lower East Fork White (66 species), the Blue-Sinking (58), and the Lower White (51) drainages, all concentrated in the southern unglaciated part of the state. Richness was predicted using nine variables, reduced from 116 and subjected to AICc importance and hierarchical partitioning. AICc importance revealed four variables associated with Plecoptera species richness, topographic wetness index, HUC8 area, % soil hydrolgroup C/D, and % historic wetland ecosystem. Hierarchical partitioning indicated topographic wetness index, HUC8 area, and % cherty red clay surface geology as significantly important to predicting species richness. This analysis highlights the importance of hydrology and glacial history in species richness of Plecoptera. The accumulated data are primed to be used for monograph production, niche modeling, and conservation status assessment for an entire assemblage in a large geographic area.

Comparative riverscape genomics of the rainbow darter (Etheostoma caeruleum) in glaciated and unglaciated environments.

Periodic glaciation during the Quaternary period shaped the contemporary riverscape and distribution of freshwater fishes in the Mississippi River drainage of central North America. The rainbow darter (Etheostoma caeruleum) is a member of this ichthyofauna and has a disjunct distribution in glaciated and unglaciated environments west of the Mississippi River. Based on glacial history of the region, there are different expectations on the observed spatial genetic structure of populations in these environments. The aim of this study was to utilize genome‐wide SNP data to compare the population genomic structure of the rainbow darter in river networks with disparate glacial histories; the Volga River in the glaciated upper Mississippi River basin and the Meramec River in the unglaciated Ozark Plateau. Individuals were sampled from localities within each river system at distances dictated by the organismal life history and habitat preferences. Riverscape analyses were performed on three datasets: total combined localities of both rivers and one for each river independently. The results revealed a lasting influence of historic glaciation on the population genomic structure of rainbow darter populations. There was evidence of population expansion into the glaciated northern region following glacial retreat. The population genetic signature within the Volga River did not fit expectations of the stream hierarchy model, but revealed a pattern of repeated colonization and extirpation due to cyclic glaciation. The population within the unglaciated Meramec River adhered to the stream hierarchy model, with a directional order of genetic diversity based on the life history and habitat preferences of the species. These results demonstrate the importance of considering the geologic and climatic history of a region as well as the life history of an organism when interpreting spatial genetic patterns.

How a New Paradigm Explains Topographic Map Drainage System and Erosional Landform Evidence in the Fremont County Royal Gorge Area, Colorado, USA

A new Cenozoic geologic and glacial history paradigm (new paradigm) describes massive and prolonged continental ice sheet meltwater floods that eroded the Colorado Royal Gorge area and surrounding regions and which were diverted in east, northeast, and even north directions as uplift of a thick ice sheet created deep “hole” rim gradually occurred (the thick ice sheet was located where North American ice sheets are usually recognized to have existed). A deep “hole” rim segment followed what is now the northern and central Colorado east-west continental divide southward to the Arkansas River headwaters area and then continued south along the Sangre de Cristo Mountains crestline to at least the Purgatoire River-Canadian River drainage divide and may have continued east from that point along a less well-defined zone beginning with what is now the Purgatoire River-Canadian River drainage divide. Diverging and converging valley complexes, barbed tributaries, and Arkansas River and other drainage route direction changes (easily seen on United States Geological Survey detailed topographic maps) are interpreted to have developed as the south-oriented floodwaters first flowed across the rising deep “hole” rim to reach the south- and southeast-oriented Rio Grande River drainage basin and were subsequently blocked by deep “hole” rim uplift and diverted to flow in east, northeast, and north directions. The accepted Cenozoic geologic and glacial history paradigm (accepted paradigm) has to date been unable to satisfactorily explain the detailed topographic map drainage system and erosional landform evidence and the new and accepted paradigms are incommensurable and lead to quite different Cenozoic geologic and glacial histories.

The evolutionary heritage and ecological uniqueness of Scots pine in the Caucasus ecoregion is at risk of climate changes

Scots pine is one of the most widely occurring pines, but future projections suggest a large reduction in its range, mostly at the southern European limits. A significant part of its range is located in the Caucasus, a global hot-spot of diversity. Pine forests are an important reservoir of biodiversity and endemism in this region. We explored demographic and biogeographical processes that shaped the genetic diversity of Scots pine in the Caucasus ecoregion and its probable future distribution under different climate scenarios. We found that the high genetic variability of the Caucasian populations mirrors a complex glacial and postglacial history that had a unique evolutionary trajectory compared to the main range in Europe. Scots pine currently grows under a broad spectrum of climatic conditions in the Caucasus, which implies high adaptive potential in the past. However, the current genetic resources of Scots pine are under high pressure from climate change. From our predictions, over 90% of the current distribution of Scots pine may be lost in this century. By threatening the stability of the forest ecosystems, this would dramatically affect the biodiversity of the Caucasus hot-spot.

Detrital zircon geochronology and provenance of Pleistocene loess and contributing glacial sources, midcontinental USA

Midcontinental North America contains extensive loess deposits that have been studied with geochemical, mineralogical, and stratigraphic techniques to explore glacial history and sediment provenance. Much of this analysis has focused on loess deposits that accumulated during the last glacial maximum (LGM), in part because of the ubiquity of unweathered Peoria Silt deposits. We test the utility of detrital zircon (DZ) U–Pb dating, which offers a weathering-resistant approach to the determination of loess provenance and can uniquely be applied to both LGM and older (commonly more altered) pre-LGM loess units. We determined DZ U–Pb age distributions (n = 1385 U–Pb ages) for the lobes that contributed sediment to Mississippi and Illinois River valley loess: Des Moines Lobe, Superior Lobe, Green Bay Lobe, Lake Michigan Lobe and Huron-Erie Lobe. We also measured DZ U–Pb age distributions (n = 4466 U–Pb ages) sampled from loess sites located along the bluffs of the Illinois River Valley and Mississippi River Valley. Samples were collected from Peoria Silt (Wisconsin Episode; Marine Isotope Stage (MIS 2)), Roxana Silt (Wisconsin Episode; MIS 3), Loveland Silt (Illinois Episode; MIS 6), and Crowley's Ridge Silt (pre-Illinois Episode).LGM glacial tills provide distinct DZ age signatures that can be used to identify glacial source contributions to loess deposits. Loess DZ age signatures in the Peoria Silt of the Illinois River Valley and the Roxana Silt of the northern lower Mississippi River Valley change temporally in a manner consistent with blockage and avulsion of the ancient Mississippi River, representing a proof-of-concept for the DZ loess provenance method in the midcontinent. The loess DZ record also provides insight into the pre-LGM drainage network and glacial lobe extents. DZ signatures for the MIS 3 Roxana Silt, along the Mississippi Valley, implies minimal sediment input from the Des Moines Lobe, suggesting this lobe was short-lived, existed further northward, or provided only limited sediment to meltwater valleys during this time. The dominant Huron-Erie Lobe signature throughout pre-LGM loess units shows that ice flow from the eastern Labrador Dome was a persistent feature during earlier glaciations. Finally, some western-derived DZ ages in pre-MIS 2 loess of the middle and lower Mississippi River Valley suggests that drainage networks that followed the modern Missouri River system were present prior to the LGM and integrated with the Mississippi River system.

Genetic Causes and Consequences of Sympatric Morph Divergence in Salmonidae: A Search for Mechanisms.

Repeatedly and recently evolved sympatric morphs exhibiting consistent phenotypic differences provide natural experimental replicates of speciation. Because such morphs are observed frequently in Salmonidae, this clade provides a rare opportunity to uncover the genomic mechanisms underpinning speciation. Such insight is also critical for conserving salmonid diversity, the loss of which could have significant ecological and economic consequences. Our review suggests that genetic differentiation among sympatric morphs is largely nonparallel apart from a few key genes that may be critical for consistently driving morph differentiation. We discuss alternative levels of parallelism likely underlying consistent morph differentiation and identify several factors that may temper this incipient speciation between sympatric morphs, including glacial history and contemporary selective pressures. Our synthesis demonstrates that salmonids are useful for studying speciation and poses additional research questions to be answered by future study of this family.

Cosmogenic nuclide exposure age scatter records glacial history and processes in McMurdo Sound, Antarctica

Abstract. The preservation of cosmogenic nuclides that accumulated during periods of prior exposure but were not subsequently removed by erosion or radioactive decay complicates interpretation of exposure, erosion, and burial ages used for a variety of geomorphological applications. In glacial settings, cold-based, non-erosive glacier ice may fail to remove inventories of inherited nuclides in glacially transported material. As a result, individual exposure ages can vary widely across a single landform (e.g., moraine) and exceed the expected or true depositional age. The surface processes that contribute to inheritance remain poorly understood, thus limiting interpretations of cosmogenic nuclide datasets in glacial environments. Here, we present a compilation of new and previously published exposure ages of multiple lithologies in local Last Glacial Maximum (LGM) and older Pleistocene glacial sediments in the McMurdo Sound region of Antarctica. Unlike most Antarctic exposure chronologies, we are able to compare exposure ages of local LGM sediments directly against an independent radiocarbon chronology of fossil algae from the same sedimentary unit that brackets the age of the local LGM between 12.3 and 19.6 ka. Cosmogenic exposure ages vary by lithology, suggesting that bedrock source and surface processes prior to, during, and after glacial entrainment explain scatter. 10Be exposure ages of quartz in granite, sourced from the base of the stratigraphic section in the Transantarctic Mountains, are scattered but young, suggesting that clasts entrained by sub-glacial plucking can generate reasonable apparent exposure ages. 3He exposure ages of pyroxene in Ferrar Dolerite, which crops out above outlet glaciers in the Transantarctic Mountains, are older, which suggests that clasts initially exposed on cliff faces and glacially entrained by rock fall carry inherited nuclides. 3He exposure ages of olivine in basalt from local volcanic bedrock in the McMurdo Sound region contain many excessively old ages but also have a bimodal distribution with peak probabilities that slightly pre-date and post-date the local LGM; this suggests that glacial clasts from local bedrock record local landscape exposure. With the magnitude and geological processes contributing to age scatter in mind, we examine exposure ages of older glacial sediments deposited by the most extensive ice sheet to inundate McMurdo Sound during the Pleistocene. These results underscore how surface processes operating in the Transantarctic Mountains are expressed in the cosmogenic nuclide inventories held in Antarctic glacial sediments.

Glacial landscape configuration influences channel response to flooding

AbstractThe influence of glaciation‐induced watershed configuration on channel response to flooding remains a topic of comparatively little research despite the prevalence of paraglacial landscapes. This study examines the response of Guichon Creek, a 1,200 km2 catchment in the southern interior of British Columbia, to major flood events during consecutive freshets with return periods of 20–40 years. The glacial history of the Guichon Creek landscape has influenced the spatial pattern of sediment availability to the channel, with erosion of thick glaciofluvial deposits located adjacent to the mainstem channel leading to extensive destabilization of downstream reaches. Over the two flood events, Guichon Creek widened by a factor of eight, but only downstream of sediment sources. Where sediment was not available to enter the channel, major changes in width were not observed. At least 163,000 ± 83,000 m3 and 73,890 ± 11,752 m3 of sediment entered the stream channel during the 2017 and 2018 freshets, respectively, representing an input more than 200 times the mean annual transport capacity. Between 40% and 60% of this sediment was of a sufficient caliber to be transported as bedload. While aggradation and degradation exceeding several meters in depth was observed at some sites, net increase in storage was small, indicating substantial sediment export. Specific patterns of channel change downstream of sediment input sites correspond to gradients in stream power. We present a conceptual model contrasting profile form, sediment availability, and transport capacity between a previously glaciated and a non‐glaciated basin of similar size and relief. These findings illustrate the broad implications of glacial landscape history on channel response to flooding, and have direct implications for river management, particularly as it pertains to channel stability and aquatic habitat.

Glacial geomorphology of the Kola Peninsula and Russian Lapland

ABSTRACT At present, there remains uncertainty surrounding the glacial history of the Fennoscandian Ice Sheet on the Kola Peninsula and Russian Lapland, northwest Arctic Russia. This is attributed to the lack of high-resolution ice sheet-scale geomorphological data in the region. This paper presents 245,997 landforms in a new high-resolution, glacial geomorphological map of the Kola Peninsula and Russian Lapland. Individual landforms were mapped from relief-shaded renditions of the 2 m resolution ArcticDEM alongside 3 m resolution PlanetScope Ortho Scene data in a Geographic Information System (GIS). Digital mapping was accompanied by field mapping in selected areas. The map, which is presented at a scale of 1: 675,000, will form the basis of a palaeoglaciological reconstruction of northwest Arctic Russia that will inform ice sheet dynamics – at both a regional- and ice sheet-scale – and provide an important framework through which numerical ice sheet models can be constrained.

The Heligoland Glacitectonic Complex in the southeastern North Sea: indicators of a pre‐ or early‐Elsterian ice margin

Glacial landforms are abundant in the North Sea basin and are often used to reconstruct the impact and dynamics of ice sheets during the Pleistocene. Geophysical methods have allowed the mapping and structural analysis of glacial landforms at the surface and in the subsurface to estimate the position of former ice margins in the North Sea. However, the glacial history of the southeastern North Sea remains underexplored. In this study, we present a structural analysis of Late Pliocene to Late Pleistocene sediments based on a dense grid of 2D high‐resolution multi‐channel reflection seismic data from the German sector of the southeastern North Sea. We show that the Heligoland Glacitectonic Complex (HGC) is larger than previously assumed (700 km2, 32×22 km) and characterized by three distinct zones of thrusting and deformation on two décollements. The kinematic restoration of seismic cross‐sections and dip measurements of thrust faults demonstrate that the HGC was formed by an ice lobe advancing from the southeast. To explain the origin of the HGC, we provide alternative models for its formation during a single ice advance or two ice advances in the study area. Furthermore, we validate the early or pre‐Elsterian age of the HGC based on nearby Elsterian tunnel valleys, and conclude that salt structures in the subsurface may have influenced its location.

Holocene glacier history of northeastern Cordillera Darwin, southernmost South America (55°S)

AbstractIn the Cordillera Darwin, southernmost South America, we used 10Be and 14C dating, dendrochronology, and historical observations to reconstruct the glacial history of the Dalla Vedova valley from deglacial time to the present. After deglacial recession into northeastern Darwin and Dalla Vedova, by ~16 ka, evidence indicates a glacial advance at ~13 ka coeval with the Antarctic Cold Reversal. The next robustly dated glacial expansion occurred at 870 ± 60 calendar yr ago (approximately AD 1150), followed by less-extensive dendrochronologically constrained advances from shortly before AD 1836 to the mid-twentieth century. Our record is consistent with most studies within the Cordillera Darwin that show that the Holocene glacial maximum occurred during the last millennium. This pattern contrasts with the extensive early- and mid-Holocene glacier expansions farther north in Patagonia; furthermore, an advance at 870 ± 60 yr ago may suggest out-of-phase glacial advances occurred within the Cordillera Darwin relative to Patagonia. We speculate that a southward shift of westerlies and associated climate regimes toward the southernmost tip of the continent, about 900–800 yr ago, provides a mechanism by which some glaciers advanced in the Cordillera Darwin during what is generally considered a warm and dry period to the north in Patagonia.

Application of Rock Weathering and Colonization by Biota for the Relative Dating of Moraines from the Arid Part of the Russian Altai Mountains

For the Altai Mountains’ region, especially the arid southeastern part of the Russian Altai, the data on glacier fluctuations in the Pleistocene and Holocene are still inconsistent. The study area was the Kargy River’s valley (2288–2387 m a.s.l.), a location that is not currently affected by glaciation and the glacial history of which is poorly studied. Field observations and geomorphological mapping were used to reveal the configuration of Pleistocene moraines. The relative dating method was applied to define the degree of weathering as an indicator of age. Three moraine groups of different ages (presumably MIS 6, MIS 4, and MIS 2) were identified based on a detailed investigation of their morphological features and the use of relative dating approaches. The latter were primarily based on weathering patterns. Data on the rock mineralogy, porosity, and specificity of biological colonization as an agent of weathering were obtained for the moraine debris. The studied moraines were composed of fine-grained schist, in which the specific surface area and fractality (self-similarity) were more developed in the older moraine. The growth of biota (crustose lichen and micromycetes) colonizing the rock surface led to rock disintegration and the accumulation of autochthonous fragments on the rock surface. Despite the fact that the initial stage(s) of moraine weathering affected by biota was fixed, the correlation trends of biota activity and moraine ages were not determined.

Hydromorphologial assessment of the Vjosa river at the catchment scale linking glacial history and fluvial processes

Balkan rivers are described as hotspots of biodiversity due to the limited glaciation to a few high-altitude cirques during the last ice age. Although many studies have examined local-scale highlights in biota and biodiversity, an overall hydro-morphological characterization and development assessment of these rivers during the Holocene are missing. Aim of the presented study is to put together the present and recent river dynamics and Quaternary landscape development for a comprehensive understanding of geomorphic processes and the current river morphological characteristics of the Vjosa river. This was done by linking satellite imagery and hydro-dynamic modelling to read the landscape, i.e., to determine the development of landscape units, and (i) the active channel, (ii) the active floodplain and (iii) the morphological floodplain. The digital terrain of the Vjosa River catchment, as an example of the Balkan rivers, was based on a 25 m × 25 m digital elevation model, and hydrodynamic numerical analysis was conducted with a one-dimensional step-backwater model. The application of this assessment approach enabled a clear differentiation of four different sections along the longitudinal profile of the Vjosa—mainly differentiated by the slope and partially corresponding with the confluence of tributaries. We also found that periods of glaciation imposed a strong impact on the hydro-morphological characteristics of the Vjosa River. In particular, the delineation of the active channel and the active floodplain exhibited two different morphological reaches. The first reach exhibits a clear incision of the river into fluvial deposits when the historical sediment supply was high, and the second reach occurs downstream where the current sediment supply is equal or higher than that during the Pleistocene or earlier periods. These differences in hydro-morphological development exert a strong impact on the floodplain development and the human use of these reaches. Thus, despite the given uncertainties due to the lack of bathymetric accuracy, the hybrid assessment approach is useful for the hydro-morphological characterization of the Vjosa river and the identification of landscape forming processes on the catchment scale.

The roles of dispersal limitation, climatic niches and glacial history in endemism of the North American bryophyte flora.

Bryophytes (mosses, liverworts, and hornworts) tend to have very large geographic ranges, which impedes progress toward understanding the drivers of diversification and extinction. This study aimed to investigate whether North American endemics differ geographically from more widespread species and whether differences in climatic niche or traits related to dispersal and establishment differ between endemics and more widespread species. All available herbarium records of bryophytes from North America north of Mexico (106 collections) were used. Traits related to dispersal were obtained from the literature. Analyses tested whether range sizes and extents differed between endemics and nonendemics, and whether trait differences were associated with endemism. Climate data were used to determine whether differences in niche breadth are present between endemics and nonendemics, and whether suitable climate for endemics occurs outside North America. Nonendemics have range sizes twice as large as endemics and they occur farther north and have greater longitudinal extents. However, they do not have the widest niche breadths and do not differ in spore size (with few exceptions) or sexual condition. Asexual propagules are more prevalent among nonendemics. Climatic models indicate that substantial areas of climate suitable for endemics exist outside of North America. Distributions of endemics and nonendemics are consistent with an important role of glaciation in shaping the North American bryophyte flora. Endemics are not limited to the continent based on a lack of suitable climate elsewhere or by spore size or sexual condition.

Holocene seismic stratigraphy of the southern arms of Lago Argentino

Lago Argentino hosts various calving glaciers, including the famous Perito Moreno. Although the onland Holocene glacier dynamics is rather well constrained, the paleoenvironments developed in association with a retreating ice front remain largely unknown. A detailed analysis of high-resolution seismic reflection profiles acquired in the southern arms of Lago Argentino has allowed the identification of several unconformities within the lacustrine sedimentary infill. Four seismostratigraphic sequences have been identified in Brazo Rico and three in Brazo Sur. These sequences are separated by three erosive unconformities in Brazo Rico and two in Brazo Sur, and reflect the sedimentation of a pre-Holocene deep basin in a proglacial lake. The older unconformities are associated with instability events within the basin which triggered several mass movements, possibly related to enhanced seismic activity. The younger erosive unconformities were correlated with the “Pearson 1a/Frias 1 advance”, the major glacier advance in the Holocene of the Lago Argentino Basin. This research highlights the importance of studying the glaciolacustrine sediments, representing decisive records of the glacial history and palaeoclimate, which could help unveiling the factors controlling glacier dynamics in the basin and reconstructing the deglacial landscape of the area.

Late Quaternary glacial advances and equilibrium-line altitude changes in a semi-arid region, Suru Basin, western Himalaya

This study examines the late Quaternary glacial history of Suru Basin and its associated tributary valleys (i.e., Achambur, Kangriz, Shafat, Rangdum, and Pensilugnpa), western Himalaya, based on the data collected from field surveys (2015–2019), satellite images, and optically stimulated luminescence (OSL) dating. The glaciers in Suru Basin have fluctuated greatly throughout the Marine Isotope Stages (MIS) 3 and 2 to the Little Ice Age (LIA), and are critical in understanding the linkages between regional and global climate change. Here, we present a detailed record of five major glacial advances of decreasing magnitude, dated 33–23 ka, 16 ka, 13–11 ka, 10–7.3 ka, 2.8–2.3 ka, and a minor advance dated 0.7–0.4 ka. These five major glacial advances are named from oldest to youngest as Suru-I to V, based on their optical chronology, geographical position, moraine stratigraphy, and glacially polished rock surfaces. Whereas, the equilibrium-line altitude (ELA) ascended by ∼538 m from the oldest glacial advance (Suru-I) to the present-day, followed by four other events (Suru-II, III, IV, and V) with ascended ELAs of ∼522, ∼399, ∼243, and 215 m, respectively. Suru Basin has lost ∼502 km2 in its glaciated area and ∼163 km3 in ice volume from Suru-I to the present-day. The magnitude of glacier extent decreased from the MIS 3 and 2, early to late-Holocene, and LIA. The timing of these glacial advances is coarsely in agreement with North Atlantic millennial-scale climate oscillations (Heinrich events), signifying the probable correlation between these abrupt climate changes and glacial fluctuations in this semi-arid region of the Himalaya.