Relict Pleistocene Research Articles

Forecast the Habitat Sustainability of Schoenus ferrugineus L. (Cyperaceae) in the Southern Urals under Climate Change.

An analysis of the current potential range of the Pleistocene relict plant species Schoenus ferrugineus and modeling of changes in its future range under moderate (RCP4.5) and strong (RCP8.5) climate change in the middle and second half of the 21st century were carried out. The MaxEnt program was used for modeling. Climate variables from CHELSA Bioclim, the global digital soil mapping system SoilGrids, and a digital elevation model were used as predictors. Modeling has shown that climate change will lead to a significant reduction in the suitability of S. ferrugineus habitat conditions by the mid-21st century. The predicted changes in the distribution of habitats of S. ferrugineus, a diagnostic species of calcareous mires and an indicator of their ecological state, indicate a possible strong transformation of wetland complexes in the Southern Urals region even under moderate climate change. A reduction in the distribution of S. ferrugineus at the eastern limit of its range will also be facilitated by more frequent extreme droughts. To maintain the distribution of S. ferrugineus on the eastern border of its range, a number of measures are proposed to mitigate the negative consequences of climate change, contributing to the preservation of the hydrological regime of calcareous mires.

Genetic Diversity and Phylogeography of a Turf-Forming Cosmopolitan Marine Alga, Gelidium crinale (Gelidiales, Rhodo-Phyta).

Cosmopolitan species are rare in red algae, which have a low-dispersal capacity unless they are dispersed by human-mediated introductions. Gelidium crinale, a turf-forming red alga, has a widespread distribution in tropical and temperate waters. To decipher the genetic diversity and phylogeography of G. crinale, we analyzed mitochondrial COI-5P and plastid rbcL sequences from collections in the Atlantic, Indian, and Pacific Oceans. Phylogenies of both markers statistically supported the monophyly of G. crinale, with a close relationship to G. americanum and G. calidum from the Western Atlantic. Based on the molecular analysis from these materials, Pterocladia heteroplatos from India is here merged with G. crinale. Phylogeny and TCS networks of COI-5P haplotypes revealed a geographic structure of five groups: (i) Atlantic-Mediterranean, (ii) Ionian, (iii) Asian, (iv) Adriatic-Ionian, and (v) Australasia-India-Tanzania-Easter Island. The most common ancestor of G. crinale likely diverged during the Pleistocene. The Bayesian Skyline Plots suggested the pre-LGM population expansion. Based on geographical structure, lineage-specific private haplotypes, the absence of shared haplotypes between lineages, and AMOVA, we propose that the cosmopolitan distribution of G. crinale has been shaped by Pleistocene relicts. The survival of the turf species under environmental stresses is briefly discussed.

Central European forest–steppe: An ecosystem shaped by climate, topography and disturbances

AbstractThe occurrence and origin of dry grasslands and their rich biota in the moderately humid Central‐European climate have fascinated scientists for over a century. Modern palaeoecological and phylogeographical data support earlier hypotheses that these grasslands are late Pleistocene relicts and can therefore be considered part of the Eurasian forest–steppe biome. However, it is still unclear which factors fostered the maintenance of steppe patches in Central Europe throughout the Holocene. Here, we provide an overview of the main hypotheses, which stress, respectively, the effects of climate, edaphic conditions and disturbances. We then develop a general conceptual framework on how these three factors interact to form forest–steppe mosaics. We thereby emphasize the role of topography as a crucial control on forest–steppe patterns at the landscape scale. Topography is related to several mechanistic drivers that influence vegetation processes, such as near‐surface microclimate and soil formation. Consequently, topographic variation allows both forest and steppe patches to occur beyond their macroclimatic niche, favouring the development of forest–steppe mosaics. To illustrate our framework, we demonstrate the interactive effect of macroclimate and topography on the occurrence of steppe patches at 108 selected Central European forest–steppe sites. Although we developed our framework focusing on the current distribution of Central European forest–steppe, we suggest that it contributes to the understanding of similar transitions between temperate forest and steppe biomes in the past as well as elsewhere in the world.

Rapid seafloor changes associated with the degradation of Arctic submarine permafrost

SignificanceTemperature increases in Arctic regions have focused attention on permafrost degradation on land, whereas little is known about the dynamics of extensive glacial-age permafrost bodies now submerged under the vast Arctic Continental shelves. Repeated high-resolution bathymetric surveys show that extraordinarily rapid morphologic changes are occurring at the edge of the continental slope of the Canadian Beaufort Sea along what was once the seaward limit of relict Pleistocene permafrost. How widespread similar changes are on the Arctic shelves is unknown, as this is one of the first areas in the Arctic subjected to multiple multibeam bathymetric surveys. Rapid morphologic changes associated with active submarine permafrost thawing may be an important process in sculpturing the seafloor in other submarine permafrost settings.

ГОРЕЧАВКА ЛЕЖАЧАЯ GENTIANA DECUMBENS L. FIL. (GENTIANACEAE) – РЕДКИЙ РЕЛИКТОВЫЙ ВИД ФЛОРЫ ЮЖНОГО УРАЛА

The article presents a review of data on the rare Pleistocene relict species of the Siberian origin of the flora of the South Ural – Gentiana decumbens L. fil. (Gentianaceae Juss.). The species is included in the third edition of the Red Data Book of the Republic of Bashkortostan (RB) [2021] in the conservation status: category 2 – a species that is declining in abundance and/or distribution; vulnerable species (VU); II priority (Bashkir Trans-Urals). In the RB there is an isolated relict fragment of the range of G. decumbens on the eastern slope of the Southen Urals – in the Baymak district. Currently, 10 locations of the species are known. The known populations of the species are small, fragmented, which makes the species vulnerable. Populations are subject to negative anthropogenic and natural influences, to which the species is weakly resistant. Only one population of G. decumbens has territorial protection, which is located within the limits of the botanical natural monument "The population of Allium hymenorhizum near Bogachevo village" in the Baymak district. The necessity of a set of additional measures for the protection of G. decumbens in situ and ex situ is substantiated.

The Depositional Environments in the Cilento Offshore (Southern Tyrrhenian Sea, Italy) Based on Marine Geological Data

The depositional environments offshore of the Cilento Promontory have been reconstructed based on the geological studies performed in the frame of the marine geological mapping of the geological sheet n. 502 “Agropoli”. The littoral environment (toe-of-coastal cliff deposits and submerged beach deposits), the inner continental shelf environment (inner shelf deposits and bioclastic deposits), the outer continental shelf environment (outer shelf deposits and bioclastic deposits), the lowstand system tract and the Pleistocene relict marine units have been singled out. The littoral, inner shelf and outer shelf environments have been interpreted as the highstand system tract of the Late Quaternary depositional sequence. This sequence overlies the Cenozoic substratum (ssi unit), composed of Cenozoic siliciclastic rocks, genetically related with the Cilento Flysch. On the inner shelf four main seismo-stratigraphic units, overlying the undifferentiated acoustic basement have been recognized based on the geological interpretation of seismic profiles. On the outer shelf, palimpsest deposits of emerged to submerged beach and forming elongated dunes have been recognized on sub-bottom profiles and calibrated with gravity core data collected in previous papers. The sedimentological analysis of sea bottom samples has shown the occurrence of several grain sizes occurring in this portion of the Cilento offshore.

European freshwater mussels (Unio spp., Unionidae) in Siberia and Kazakhstan: Pleistocene relicts or recent invaders?

Unionidae is a species-rich family of large freshwater mussels with an almost worldwide distribution. In many regions of the world, these mussels are imperiled. Northern Asia, excluding the Far East, is an excellent example of a region with a sharply impoverished fauna of the Unionidae as recently thought with one native species. Since the end of the 19th century, two freshwater mussel species of the genus Unio (U. pictorum and U. tumidus) were repeatedly recorded in Siberia. In the course of this study, these finds are confirmed both morphologically and genetically, the number of known occurrences of these mussels in the waterbodies of Asiatic Russia and Kazakhstan has drastically increased, and the third species, globally endangered U. crassus, was found in the Ob’ River basin. The unique U. tumidus haplotype discovered from the Upper Irtysh River basin is of probable relic origin, which may indicate the presence of a Pleistocene refugium there. Due to natural environmental changes during the last century, several genera of freshwater Mollusca that previously inhabited Western Siberia, but went completely extinct in the Pleistocene, have started to recover the North Asiatic part of their former ranges. The case of Unio is exceptional since the recovery of its lost range goes not exclusively with the humans’ help but also involves the natural mechanisms of dispersal and range extension, and also because these mussels are disappearing in other parts of the world and are placed in the IUCN Red List of Threatened Species.

Diversity and distribution of vascular plants within the treeline ecotone in Mount Iremel (Southern Urals, Russia).

BackgroundDuring the last 100 years, rapid advances of trees towards higher elevations and latitudes have been recorded for various regions worldwide, including the Ural Mountains. Climate warming and tree cover increases can lead to significant changes in the high-mountain vegetation. Direct observations on the vegetation of high-mountain regions provide evidence for an increase in the species diversity of plants at high elevations and changes in the composition of the alpine communities. This study investigated the diversity and distribution of vascular plants within the present-day treeline ecotone in Mount Iremel, the Southern Urals.New informationThe dataset (Trubina and Nesterkov 2021, available from the GBIF network at https://www.gbif.org/dataset/284f1484-10b7-4ef5-87b7-9de1159e6b42) presents the results of an assessment of species richness and frequency of vascular plants at the different elevation levels (from 1203 to 1348 m a.s.l.) and different biotopes (birch-spruce shrub forest, birch-spruce sparse forest and spruce forest with fragments of meadow plant communities) within the treeline ecotone in Mount Iremel, Southern Urals. Observations were carried out at 700 sampling plots with two estimation methods: small-size plot (0.5 × 0.5 m) sampling (672 plots in total) and large-size plot (10 × 10 m) sampling (28 plots). The dataset includes 700 sampling events (= sampling plots), corresponding to 5585 occurrences (vascular plants, mainly identified to species) observed during July 2003. Only occurrences containing plant taxa (occurrenceStatus = present) have been provided. The dataset includes information about distribution and frequency of the Ural endemic species (Anemone narcissiflora subsp. biarmiensis (Juz.) Jalas, Calamagrostis uralensis Litv., Cerastium krylovii Schischk. & Gorczak., Festuca igoschiniae Tzvel., Hieracium iremelense (Elfstr.) Üksip, Lagotis uralensis Schischk, Pleurospermum uralense Hoffm.) and the Pleistocene relict species (Alopecurus magellanicus Lam., Bistorta vivipara (L.) Delarbre, Cerastium pauciflorum Stev. ex. Ser., Pedicularis oederi Vahl, Saussurea controversa DC., Swertia perennis L.). The dataset also provides information that can be useful for estimating biodiversity and plant communities composition within the treeline ecotone at a specified time period and contributes to the study of biodiversity conservation in the Ural Region.

Marine geological maps of the Campania region (Southern Tyrrhenian Sea, Italy): Considerations and contributions to a different scale of geological survey

Marine geological maps of the Campania region have been constructed both to a 1:25.000 and to a 1:10.000 scale in the frame of the research projects financed by the Italian National Geological Survey, focusing, in particular, on the Gulf of Naples (Southern Tyrrhenian Sea), a complex volcanic area where volcanic and sedimentary processes strongly interacted during the Late Quaternary and on the Cilento Promontory offshore. In this paper, the examples of the geological sheets n. 464 “Isola di Ischia” and n. 502 “Agropoli” have been studied. The integration of the geological maps with the seismo-stratigraphic setting of the study areas has also been performed based on the realization of interpreted seismic profiles, providing interesting data on the geological setting of the subsurface. The coastal geological sedimentation in the Ischia and Agropoli offshore has been studied in detail. The mapped geological units are represented by: i) the rocky units of the acoustic basement (volcanic and/or sedimentary); ii) the deposits of the littoral environment, including the deposits of submerged beach and the deposits of toe of coastal cliff; iii) the deposits of the inner shelf environment, including the inner shelf deposits and the bioclastic deposits; iv) the deposits of the outer shelf environment, including the clastic deposits and the bioclastic deposits; v) the lowstand system tract; vi) the Pleistocene relict marine units; vii) different volcanic units in Pleistocene age. The seismo-stratigraphic data, coupled with the sedimentological and environmental data provided by the geological maps, provided us with new insights on the geologic evolution of this area during the Late Quaternary.

Temporal and Spatial Distribution of Surface Sediment and Its Implications in the Yangtze Subaqueous Delta

Characteristics of sediments vary significantly temporally and spatially in the Yangtze subaqueous delta and adjacent East China Sea shelf due to complicated dynamic conditions. Magnetic properties of sediments are sensitive to hydrodynamics and provenance, and therefore can indicate sediment transportation and deposition. High-resolution surface sediments collected in different seasons and years from the Yangtze subaqueous delta and neighboring East China Sea shelf were subjected to environmental magnetic analyses. In combination with granulometric analysis, this paper discusses temporal and spatial variations of magnetic properties and their implications for indicating sediment transportation, sediment source identification, and hydrodynamic response. The results show that magnetic parameters SIRM and XARM/SIRM suggest sediment transportation path from the Yangtze River into the East China Sea, with majority migrating to the south and southeast and then deposited to the west of 123°E, while a little fine sediment delivered to the northeast in summer. Cluster analysis demonstrates three sedimentation districts according to magnetic properties and particle size in the study area, which represent modern Yangtze sediment, late Pleistocene relict sand, and their mixture, respectively. Temporal-spatial changes in particle size of sediments suggests erosion outside the North Branch in the past few years, while opposite trend of changes on particle size of surface sediment in the adjacent area might reflect different degrees of erosion.

Noble savages: human-independent Rattus rats in Japan

ABSTRACT Brown (Rattus norvegicus) and black (R. rattus sensu lato) rats are among the world’s most widespread and important invasive animals; however, there are very few studies of their natural history in natural habitats within their native ranges. Both taxa are native to Japan and still occur in natural habitats there, but have been traditionally treated by zoologists working in the country as invasive pests limited to cities and agricultural lands. We used thermal imaging and snow tracking to conduct the first study of status, distribution and behavioural ecology of remnant human-independent populations of these species in Japan. We found both species still living in natural habitats away from human settlements: brown rat is a rare species in wetlands on the main islands and in upland forests on Hokkaido, while the native taxon of R. rattus species complex, the Asian house rat (R. tanezumi sensu stricto) inhabits remnant deciduous old-growth forests, as well as evergreen subtropical forests, in the south of the country. Such knowledge is critically important for understanding the rats’ evolutionary history, invasion biology and behaviour. Future molecular studies should aim to clarify the origin of these populations: possibly they are Pleistocene relicts threatened by hybridisation with rats of related non-native taxa.

Holocene fish assemblages provide baseline data for the rapidly changing eastern Mediterranean

The eastern Mediterranean marine ecosystem is undergoing massive modification due to biological invasions, overfishing, habitat deterioration, and climate warming. Our ability to quantify these changes is severely hindered by the lack of an appropriate baseline; most ecological datasets date back a few decades only and show already strong signatures of impact. Surficial death assemblages (DAs) offer an alternative data source that provides baseline information on community structure and composition. In this study, we reconstruct the marine fish fauna of the southern shallow Israeli shelf before the opening of the Suez Canal based on fish otoliths. We quantify the age of the otolith DAs by radiocarbon dating, and describe its taxonomic composition, geographic affinity, and trophic structure. Additionally, we test by radiocarbon dating the hypothesis that Bregmaceros, a presumed Lessepsian invader with continuous presence in the Mediterranean throughout the late Cenozoic, is a relict species. The otolith DA dates back to the mid-Holocene because 75% of the dated otoliths of the native species are older than the opening of the Suez Canal in 1869, suggesting that the DA is a proper baseline for quantifying modern impacts. Consistently, 97% of the otoliths and 88% of the species we collected belong to native Mediterranean species. The native anchovy Engraulis encrasicolus dominates the DAs, although gobiids are the most diverse group (14 species, 28%). The DAs show similar trophic structure to present-day pristine Mediterranean coastal fish assemblages. Two non-indigenous species are recorded here for the first time in the Mediterranean Sea, Amblygobius albimaculatus and Callogobius sp., highlighting the importance of DAs for detecting non-indigenous species. Finally, Bregmaceros otoliths are modern, not supporting the previous hypothesis that the taxon is a Pleistocene relict.

Marine geological maps of the Campania Region (Southern Tyrrhenian sea, Italy): considerations and contributions to a different scale of geological survey

Marine geological maps of the Campania region have been constructed both to 1:25.000 and to a 1:10.000 scales in the frame of research projects financed by the Italian National Geological Survey, focusing, in particular, on the Gulf of Naples (Southern Tyrrhenian sea), a complex volcanic area where volcanic and sedimentary processes strongly interacted during the Late Quaternary and on the Cilento Promontory offshore. In this paper the examples of the geological sheets n. 464 “Isola di Ischia” and n. 502 “Agropoli” have been studied. The integration of the geological maps with the seismo-stratigraphic setting of the study areas has also been performed based on the realization of interpreted seismic profiles, providing interesting data on the geological setting of the subsurface. The coastal geological sedimentation has been studied in detail in the Ischia and Agropoli offshore. The mapped geological units are represented by: i) the rocky units of the acoustic basement (volcanic and/or sedimentary), ii) the deposits of the littoral environment, including the deposits of submerged beach and the deposits of toe of coastal cliff, iii) the deposits of the inner shelf environment, including the inner shelf deposits and the bioclastic deposits, iv) the deposits of the outer shelf environment, including the clastic deposits and the bioclastic deposits, v) the Lowstand System Tract, vi) the Pleistocene relict marine units, vii) different volcanic units, Pleistocene in age. The seismo-stratigraphic data, coupled with the sedimentological and environmental data provided by the geological maps, allow to give new insights on the geologic evolution of this area during the Late Quaternary.

Relict Pleistocene calcareous tufa of the Chlupáčova sluj Cave, the Bohemian Karst, Czech Republic: A petrographic and geochemical record of hydrologically-driven cave evolution

The tufas of the presently shallow Chlupáčova sluj Cave document an unusual history of deeper to shallower hydrologic processes in cave evolution. The wider geological context of the cave, along with fluid inclusion and stable isotope (C and O) analyses of calcite from tectonic veins cutting through its wallrock, are evidence of the origin of the cave in the deeper subsurface, under the influence of ascending 25–70 °C warm, saline (2.0–22.3 wt% eq. NaCl) waters driven by regional hypogene processes. The formation of calcite veins, which occurred at 700–400 ka, was probably coeval with the early stages of cave development. However, two generations of tufa formed in the later Pleistocene during the mature shallow-subsurface stage of cave development when daylight and cold meteoric waters penetrated the cave through ceiling windows and tectonic fractures.The first-generation tufa, which consists of cauliflower-like aggregates of hollow, outward-radiating carbonate tubules covered with isopachous banded calcite cements, is interpreted as ancient bryophyte tufa that was deposited about 620 ± 140–530 ± 110 ka. The presence of microscopic biomorphic fabrics resembling micro-stromatolites, calcareous algal chambers, calcite crystals with cloudy cores and clear sparitic rims, and specific biomarkers identified in tufa extracts suggest that, in addition to mosses, algae and bacteria may have also been instrumental in promoting the deposition of tufa. Tufa stable isotope (C and O) characteristics and fluid inclusion contents point to deposition of this first-generation tufa from fresh water with a minor admixture of higher hydrocarbons at the surface temperature.Post-dating the first-generation tufa, minute grains of exotic minerals (e.g. stibnite, gothic-arch calcite, gypsum, Mn-minerals, opaline silica) and sparry calcite were precipitated in the tufa moulds and between carbonate tubules as cements. These minerals suggest at least one event in which hydrothermal waters entered the cave from below after deposition of the first tufa from cool meteoric waters. In this hydrothermal phase, the cave may have been a hot spring.The second-generation tufa originated during the Riss – Würm Interglacial at 121 ± 2.1–107 ± 2.6 ka, following a period of intense water erosion that partly erased older spelean deposits from cave walls. This tufa consists of highly porous, friable, crudely laminated carbonate sediments with floral and molluscan remains, characteristic of common cold-water karstic tufa. This and the earlier tufa were, in turn, covered by later fine-grained cave sediments, contributing to the preservation of Pleistocene tufa that records an alternation of deep and shallow waters in the cave over at least the last 500,000 years.

Effects of Management Treatments on Regeneration of a Geographically Disjunct, Relictual Hybrid Aspen (Populus xsmithii) Population in the Central Great Plains, USA.

Populus xsmithii is an uncommon hybrid of quaking aspen (Populus tremuloides) and bigtooth aspen (Populus grandidentata). Like its parents, Populus xsmithii is an early successional member of boreal forest communities, dependent on disturbance events that clear areas of competitive stems and spur an increase in clonal suckering. In recent years, aspen dieback has been noted across much of the western United States, a condition characterized by mortality of older stems and a lack of recruitment of suckers to maturity. In the Niobrara River Valley of Cherry County, Nebraska, USA, a disjunct population of Pleistocene relict Populus xsmithii has been targeted for management via clearing of competitive conifer species and establishment of fenced refugia to protect suckers from herbivory. The stands currently contain abundant suckers, which occur in three types of sites: the fenced refugia created by managers, the open habitat cleared of other species in the stands, and the woodpiles left by said clearing. This study assessed the growth and vigor of these aspen suckers over a nine-month period (summer 2013-spring 2014) and compared the effects of different site treatments. We found that aspen suckers in the open areas were significantly shorter, had smaller basal diameter, and had higher damage scores than those in the two protected site types (fenced and woodpile). Because this population is on the margin of the distribution for aspen, evaluating the effectiveness of management techniques will provide valuable information for those who seek to ensure the survival of this aspen population and others.

Prospectando rochas fluviais e artefatos do Paleolítico Médio Africano descobertos ao longo do Rio Cunene, fronteira entre Angola e Namíbia

Vestígios líticos do Paleolítico Médio Africano (PMA) preservados em corredores ribeirinhos como o perene Rio Cunene atesta a presença de atividades pré-históricas ao longo da atual divisa entre Angola e Namíbia. Próximo à Serra Cafema, mais de 30 vestígios líticos preservados em um contexto a céu aberto (plein-air) incluem lascas de quartzito, núcleos e pontas com alguma abrasão e polimento nos gumes, incluindo as primeiras pontas Levallois encontradas nesta região da África. Uma vez que a arqueologia desta região é pobremente conhecida, estas coleções culturais permitem correlações iniciais e fornecem uma base para reconstrução da proveniência, da procura e da produção de artefatos durante o PMA. Para avaliar as potenciais áreas-fonte de matéria-prima nesta região, métodos de contagem de seixos e avaliações composicionais foram conduzidos nos vestígios e no aluvião Quaternário (Qal) do terraço do rio. A fonte primária em potencial mais próxima de quartzito está em afloramentos rochosos localizados dentro de 2 km de distância do sítio, mas áreas-fonte confirmadas não foram identificadas especificamente. Uma hipótese emergente é que o Qal no terraço do Rio Cunene era uma fonte preferida para coleta de quartzito enquanto matéria prima pelos grupos móveis de caçadores-coletores durante o PMA após 225 mil anos atrás.

Tracing Sediment Erosion in the Yangtze River Subaqueous Delta Using Magnetic Methods

AbstractWe assessed the usefulness of magnetic properties for tracing sediment erosion in a deltaic environment. Surface and core sediments from the Yangtze River subaqueous delta were subjected to magnetic, granulometric, geochemical, and radionuclide analyses. Based on magnetic properties and particle size, the surface sediments can be divided into three groups. Groups I and II have a similar particle size distribution and geochemical composition, but the former has higher values of magnetic susceptibility (χ) and saturation isothermal remanent magnetization (SIRM). We interpret Group I as consisting of modern sediments, while Group II represents previously buried sediments that have undergone significant reductive diagenesis and that have been subsequently exposed by erosion. Group III has coarser particle size, which reflects the mixing of delta sediments with Pleistocene relict sands. Two cores from the areas occupied by Groups I and II have significantly different magnetic profiles. Core A3‐4 (Group II) records a partial loss of magnetic mineral concentration due to diagenesis and has much lower χ, SIRM, and S−300 values than core A6‐2 (Group I). Radionuclide dating reveals that core A3‐4 sediments are older. We conclude that core A3‐4 location has undergone erosion, which is consistent with recent bathymetric survey results. We propose that the ratio of SIRM/Fe can be potentially used to trace mobilized old sediment in this environment. Our study demonstrates that magnetic properties provide a robust approach for studying sediment dynamics in this type of environment. In addition, our findings provide insights into the nature of biogeochemical processes associated with deltaic erosion.

Control factors of Holocene sedimentary infilling in a semi-closed tidal estuarine-like system: the bay of Brest (France)

This study details the sedimentary infilling of an original tidal-dominated estuary system during the final stage of the last marine transgression. The Bay of Brest is confined and connects the rivers Elorn and Aulne, to the sea of Iroise by a narrow strait encasing a well preserved paleo-channel. The compilation of high- and very-high-resolution bathymetric and seismic data, constrained by sediments datations, allows us to classify the paleo-morphology of the bay into three stepped domains: the paleo-valley floor surrounded by fluvial terraces, the central plateau, and the shallow embayments. Taking into account the main factors controlling the infilling, including sea-level rise, substratum morphology, and hydrodynamics, the stratigraphic scheme of the bay has been reconstructed. The lowstand system track (LST) is assumed to correspond to relict Pleistocene continental deposits associated with the last low sea level around 21,000calyrB.P. The transgressive phase, represented by the transgressive system track (TST), is divided into two parts. The lower part (TST1) constitutes the first stage of transgressive deposition in the bay. Starting around 9000calyrB.P. and currently conserved in the shallowest parts, it is characterized by tidal flats associated with deposits in the inner estuary. This stage ends at about 7000calyrB.P. and is separated from the upper part (TST2) by a tidal ravinement surface that occurs around 7700calyrB.P. at the foot slope. TST2 formed sand bodies in the central part of the bay between 6800 and 3000calyrB.P. These deposits, interpreted as tidal banks, are associated with the outer estuarine environment. The maximum flooding surface (MFS), dated around 3000 and 2000calyrB.P., marked the installation of a highstand system track (HST) under the combined influence of tidal currents, storms events, and anthropogenic activity. The geometry deposition of each system track is controlled at the first order by the combination of the irregular Holocene sea level rise and the inherited rocky substratum morphology. The retreat of the shoreline, and estuarine environments, is function of the successive flooding of stepped domains. The direct evolution of the volume of the assumed accumulated sea water in the bay favoured the gradual installation of the present-day hydrodynamic circulation.

Modelling the Last Glacial Maximum environments for a refugium of Pleistocene biota in the Russian Altai Mountains, Siberia

Abstract Recent botanical and zoological studies have suggested that the Altai Mountains in southern Siberia are an important refugium of the last glacial biota that used to be widespread across northern Eurasia before the Pleistocene–Holocene transition. To obtain insights into the history of this relict biota, we modelled the spatial distribution of habitats during the Last Glacial Maximum (LGM) in the Russian Altai. We prepared a map of the current vegetation of this area based on the ground-truthed remote sensing data, and modelled the distribution of the current vegetation types using the Random Forest technique with climatic predictors. The models were projected onto the CCSM3 model of the LGM climate for the Russian Altai and interpreted for 72% of its area because the remaining part is supposed to have been glaciated during the LGM. The models projected LGM predominance of desert-steppe across most of the non-glaciated area of the Russian Altai, probably associated with areas of typical steppe, tundra grasslands and some other habitat types, including forest patches in stream valleys. It is likely that during the LGM, these habitats supported the cold-adapted open-landscape biota. In the Holocene, most of the previous grassland area changed into forest or forest-steppe and the Pleistocene biota retreated, with the exception of the Chuya Basin and the Ukok Plateau in the southeast, where the habitat change was very small and desert-steppe and associated vegetation types remained preserved. This refugial area is currently rich in the relict Pleistocene species. A different history was suggested for the precipitation-rich area in the northernmost Altai (north of Lake Teletskoye), where the LGM models suggested occurrence of patches of open forest of Larix sibirica and Pinus sibirica in forest-tundra and forest-steppe landscapes. These forests may have provided the LGM refugium for the temperate forest species that currently occur in this precipitation-rich area.

Character, distribution, and ecological significance of storm wave-induced scour in Rhode Island Sound, USA

Multibeam bathymetry, collected during NOAA hydrographic surveys in 2008 and 2009, is coupled with USGS data from sampling and photographic stations to map the seabed morphology and composition of Rhode Island Sound along the US Atlantic coast, and to provide information on sediment transport and benthic habitats. Patchworks of scour depressions cover large areas on seaward-facing slopes and bathymetric highs in the sound. These depressions average 0.5–0.8 m deep and occur in water depths reaching as much as 42 m. They have relatively steep well-defined sides and coarser-grained floors, and vary strongly in shape, size, and configuration. Some individual scour depressions have apparently expanded to combine with adjacent depressions, forming larger eroded areas that commonly contain outliers of the original seafloor sediments. Where cobbles and scattered boulders are present on the depression floors, the muddy Holocene sands have been completely removed and the winnowed relict Pleistocene deposits exposed. Low tidal-current velocities and the lack of obstacle marks suggest that bidirectional tidal currents alone are not capable of forming these features. These depressions are formed and maintained under high-energy shelf conditions owing to repetitive cyclic loading imposed by high-amplitude, long-period, storm-driven waves that reduce the effective shear strength of the sediment, cause resuspension, and expose the suspended sediments to erosion by wind-driven and tidal currents. Because epifauna dominate on gravel floors of the depressions and infauna are prevalent in the finer-grained Holocene deposits, it is concluded that the resultant close juxtaposition of silty sand-, sand-, and gravel-dependent communities promotes regional faunal complexity. These findings expand on earlier interpretations, documenting how storm wave-induced scour produces sorted bedforms that control much of the benthic geologic and biologic diversity in Rhode Island Sound.