Postglacial Period Research Articles

Prevalence of the Puumala orthohantavirus Strains in the Pre-Kama Area of the Republic of Tatarstan, Russia.

Puumala orthohantavirus (PUUV) causes nephropathia epidemica (NE), a mild form of hemorrhagic fever with renal syndrome (HFRS) commonly diagnosed in Europe. The majority of HFRS cases in the European part of Russia are diagnosed in the Volga Federal District, which includes the Republic of Tatarstan (RT). The current study aims to analyze the genetic variability of PUUV in Pre-Kama region of the RT bounded by the Volga, Kama, and Vyatka rivers. In 2017, bank voles were caught in seven isolated forest traps in the Pre-Kama region and for the 26 PUUV-positive samples, the partial small (S), medium (M), and large (L) genome segment sequences were obtained and analyzed. It was determined that all identified PUUV strains belong to the Russian (RUS) genetic lineage; however, the genetic distance between strains is not directly correlated with the geographical distance between bank vole populations. One of the identified strains has S and L segments produced from one parental strain, while the M segment was supplied by another, suggesting that this strain could be the reassortant. We suggest that the revealed pattern of the PUUV strains distribution could be the result of a series of successive multidirectional migratory flows of the bank voles to the Pre-Kama region in the postglacial period.

El relicto glacial Leistus (<em>Pogonophorus) puncticeps</em> Fairmaire & Laboulbène, 1854 (Coleoptera, Carabidae): nuevos datos sobre distribución, autoecología y presencia en el Medio Subterráneo Superficial (MSS)

Numerosos muestreos realizados por el territorio peninsular, a lo largo de estas tres últimas décadas, han deparado el hallazgo de Leistus (Pogonophorus) puncticeps Fairmaire & Laboulbène, 1854 en áreas geográfi­cas en las que se desconocía su presencia hasta la fecha. Las nuevas citas amplían la distribución ibérica de la especie hacia enclaves mediterráneos meridionales, perfilando un patrón de distribución discontinuo por el tercio oriental. Al mismo tiempo, estos hallazgos revelan cierta variabilidad, muy leve, en la forma de la lámina apical del edeago. Por otro lado, se confirman los parajes quebrados y abruptos como enclaves potencialmente favorables para la supervivencia de esta especie, especialmente si disponen de laderas pedregosas. En general, las nuevas localidades en donde se ha hallado L. (P.) puncticeps, cuentan con precipitación escasa y torrencial, una pluvio­sidad media que ronda los 600-700 mm, y una notable amplitud térmica. Como novedad, y utilizando Estaciones de Muestreo Subterráneo (EMS), se ha colectado en el Medio Subterráneo Superficial (MSS). El hallazgo de esta especie en este singular medio hipogeo y en diversos enclaves ibéricos (Sierra del Moncayo, formaciones montañosas del norte de la provincia de Alicante y Sierra de María), pone de manifiesto su tendencia troglófila, y más probablemente de tipo subtroglófila. Los nuevos hallazgos, sumados a los ya conocidos, sugieren que L. (P.) puncticeps ha seguido la misma historia evolutiva que Leistus (Pogonophorus) montanus Stephens, 1827 y Leistus (Pogonophorus) parvicollis Chaudoir, 1869, constituyendo una triada de relictos glaciales, resultado de un proceso de especiación por vicarianza. Los cambios acaecidos en el período postglacial explicarían la distribución discontinua que muestra en la actualidad L. (P.) puncticeps, y su tendencia a explorar, en estos enclaves, el MSS.

Examining differences in phylogenetic composition enhances understanding of the phylogenetic structure of the shrub community in the northeastern Qinghai-Tibetan Plateau.

Periodic climatic oscillations and species dispersal during the postglacial period are two important causes of plant assemblage and distribution on the Qinghai‐Tibet Plateau (QTP). To improve our understanding of the bio‐geological histories of shrub communities on the QTP, we tested two hypotheses. First, the intensity of climatic oscillations played a filtering role during community structuring. Second, species dispersal during the postglacial period contributed to the recovery of species and phylogenetic diversity and the emergence of phylogenetic overdispersion. To test these hypotheses, we investigated and compared the shrub communities in the alpine and desert habitats of the northeastern QTP. Notably, we observed higher levels of species and phylogenetic diversity in the alpine habitat than in the desert habitat, leading to phylogenetic overdispersion in the alpine shrub communities versus phylogenetic clustering in the desert shrub communities. This phylogenetic overdispersion increased with greater climate anomalies. These results suggest that (a) although climate anomalies strongly affect shrub communities, these phenomena do not act as a filter for shrub community structuring, and (b) species dispersal increases phylogenetic diversity and overdispersion in a community. Moreover, our investigation of the phylogenetic community composition revealed a larger number of plant clades in the alpine shrub communities than in the desert shrub communities, which provided insights into plant clade‐level differences in the phylogenetic structures of alpine and desert shrub communities in the northeastern QTP.

Using mathematical modelling to investigate the adaptive divergence of whitefish in Fennoscandia

Modern speciation theory has greatly benefited from a variety of simple mathematical models focusing on the conditions and patterns of speciation and diversification in the presence of gene flow. Unfortunately the application of general theoretical concepts and tools to specific ecological systems remains a challenge. Here we apply modeling tools to better understand adaptive divergence of whitefish during the postglacial period in lakes of northern Fennoscandia. These lakes harbor up to three different morphs associated with the three major lake habitats: littoral, pelagic, and profundal. Using large-scale individual-based simulations, we aim to identify factors required for in situ emergence of the pelagic and profundal morphs in lakes initially colonized by the littoral morph. The importance of some of the factors we identify and study - sufficiently large levels of initial genetic variation, size- and habitat-specific mating, sufficiently large carrying capacity of the new niche - is already well recognized. In addition, our model also points to two other factors that have been largely disregarded in theoretical studies: fitness-dependent dispersal and strong predation in the ancestral niche coupled with the lack of it in the new niche(s). We use our theoretical results to speculate about the process of diversification of whitefish in Fennoscandia and to identify potentially profitable directions for future empirical research.

Neogene and Quaternary climate changes shaped the lineage differentiation and demographic history of Fokienia hodginsii (Cupressaceae s.l.), a Tertiary relict in East Asia

AbstractHistorical climate oscillations and tectonic events have influenced the speciation and evolutionary history of many organisms. In this study, we chose Fokienia hodginsii (Dunn) A. Henry & H. H. Thomas (Cupressaceae s.l.), a Tertiary relict conifer, for the inference of the demographic history since the Neogene. Five chloroplast regions and two single‐copy nuclear genes were amplified and sequenced in 497 individuals from 28 populations. The chloroplast data showed that F. hodginsii presented a high level of genetic diversity (H T = 0.860 ± 0.0279) and significant phylogeographic structure (N ST > G ST , P < 0.05). According tobeast analysis, the divergence time of the two major lineages indicated by the phylogenetic construction produced from chloroplast and nuclear data could be dated to the early Miocene (ca. 19.34–19.95 Ma), which coincided with the onset and intensification of the Asian monsoon. During this time, environmental adaption under the different climatic conditions on either side of the Tanaka Line could have played important roles in maintaining and/or reinforcing the divergence of the two major lineages. The ecological niche modeling results showed that F. hodginsii experienced habitat fragmentation and strengthening of genetic barriers during the Last Glacial Maximum, followed by local expansion during postglacial periods. Our findings show that paleoclimate changes since the Neogene might have triggered the extinction of all but one Fokienia species and its intraspecific lineage differentiation. This study also suggests that Tertiary relicts in subtropical and tropical areas might have had a complex evolutionary history and their intraspecific differentiation time might have been earlier than expected.

Palynological evidence of sea-surface conditions in the Barents Sea off northeast Svalbard during the postglacial period

AbstractPostglacial changes in sea-surface conditions, including sea-ice cover, summer temperature, salinity, and productivity were reconstructed from the analyses of dinocyst assemblages in core S2528 collected in the northwestern Barents Sea. The results show glaciomarine-type conditions until about 11,300 ± 300 cal yr BP and limited influence of Atlantic water at the surface into the Barents Sea possibly due to the proximity of the Svalbard-Barents Sea ice sheet. This was followed by a transitional period generally characterized by cold conditions with dense sea-ice cover and low-salinity pulses likely related to episodic freshwater or meltwater discharge, which lasted until 8700 ± 700 cal yr BP. The onset of “interglacial” conditions in surface waters was marked by a major change in dinocyst assemblages, from dominant heterotrophic to dominant phototrophic taxa. Until 4100 ± 150 cal yr BP, however, sea-surface conditions remained cold, while sea-surface salinity and sea-ice cover recorded large amplitude variations. By ~4000 cal yr BP optimum sea-surface temperature of up to 4°C in summer and maximum salinity of ~34 psu suggest enhanced influence of Atlantic water, and productivity reached up to 150 gC/m2/yr. After 2200 ± 1300 cal yr BP, a distinct cooling trend accompanied by sea-ice spreading characterized surface waters. Hence, during the Holocene, with exception of an interval spanning about 4000 to 2000 cal yr BP, the northern Barents Sea experienced harsh environments, relatively low productivity, and unstable conditions probably unsuitable for human settlements.

A complete Holocene lake sediment ancient DNA record reveals long-standing high Arctic plant diversity hotspot in northern Svalbard

Arctic hotspots, local areas of high biodiversity, are potential key sites for conservation of Arctic biodiversity. However, there is a need for improved understanding of their long-term resilience. The Arctic hotspot of Ringhorndalen has the highest registered diversity of vascular plants in the Svalbard archipelago, including several remarkable and isolated plant populations located far north of their normal distribution range. Here we analyze a lake sediment core from Ringhorndalen for sedimentary ancient DNA (sedaDNA) and geochemical proxies to detect changes in local vegetation and climate. Half of the plant taxa appeared already before 10,600 cal. yr BP, indicating rapid colonization as the ice retreated. Thermophilous species had a reoccurring presence throughout the Holocene record, but stronger signal in the early than Late Holocene period. Thus, thermophilous Arctic plant species had broader distribution ranges during the Early Holocene thermal maximum c. 10,000 cal. yr BP than today. Most of these thermophilous species are currently not recorded in the catchment area of the studied lake, but occur locally in favourable areas further into the valley. For example, Empetrum nigrum was found in >40% of the sedaDNA samples, whereas its current distribution in Ringhorndalen is highly restricted and outside the catchment area of the lake. Our findings support the hypothesis of isolated relict populations in Ringhorndalen. The findings are also consistent with main Holocene climatic shifts in Svalbard identified by previous studies and indicate an early warm and species-rich postglacial period until c. 6500 cal. yr BP, followed by fluctuating cool and warm periods throughout the later Holocene.

Tectonic Features and Stages of Evolution of the Baltic–Mezen Shear Zone in the Phanerozoic, Northwestern Russia

The general tectonic features of the Baltic-Mezen zone developed along the border of the Fennoscandian shield and the Russian Plate in the north of the East European platform, are considered. The geophysical remote methods and structural analysis were used. It has been established that the zone has a length of more than 1000 km with a width of 10–40 km and can be traced from the Gulf of Finland in the sub-latitudinal direction along the southern shores of the Lake Ladoga and the Lake Onega in the valley of the River Onega.The Baltic-Mezen zone is represented by a system of folds and faults, fracture zones and brecciation, complicating the complexes of the Archean–Paleoproterozoic basement and the Vendian–Phanerozoic cover. Throughout the zone, changes in the configuration and displacement of the axes of the magnetic anomalies are noted; on seismic sections, the systems of discontinuities penetrating the basement and cover complexes are decrypted. On the surface, the discontinuous structures of the zone are expressed in the various forms of relief, often violate and displace glacial morphostructures. Based on the analysis of materials on the nature of the paleoseismites distribution and surfaces of unconformity in the sediments of the cover, as well as the structural features of various rock complexes, a long period of development of the Baltic-Mezen zone was established during the Caledonian, Hercynian and the latest stages of deformation. The Caledonian stage was associated with the formation of paleoseismites horizons of Kukruz phase (~ 460 Ma), as well as the folded-fault structures formed in the Late Silurian–Early Devonian. The Hercynian stage was manifested by several seismic and tectonic events in the Late Devonian (Frasnian age), in the Early (Visean age) and Late (Kasimovian century) Carboniferous. The newest stage was associated with Neopleistocene glaciodynamic processes and two stages of seismic events in the late and post-glacial period, which were accompanied by activation of ancient faults and local development of folded structures. The developed scale of paleoseismic and deformation events of the Baltic-Mezen zone can be used for tectono-dynamic reconstructions based on additional analysis of materials of structural-kinematic research.

Assessment of Peat Deposits in Rwanda

The peat deposits in Rwanda are distributed over an area of 50,000 ha and were formed about the end of last glaciations period. However Akanyaru peat is 20,000 years old and contains peat of glacial and postglacial period. The studies show that Rwanda has 155 million tons of dry peat which can generate electrical energy and this deposit is sufficient to meet country’s vast energy requirements for 30 years. Hence, it was felt necessary to map prospective locations of peat and their energy potential. The result of the study and assessment of peat to power in Rwanda show that the average in-situ ash content, in-situ moisture content and in-situ bulk density of the collected peat samples are 36 wt%, 70.8 wt% and 1112 kg/m3 respectively. Their average thickness ranges from 0.9 to 7.8 m. In Finland, peat was used as fuel in 1996 and produced 10% of total installed capacity. Rwanda has the same operational peat power plant in Gishoma: Rusizi District generating 15 MW connected to the national electrical grid. A peat-fuelled power plant is under construction and is expected to generate 80 MW. This plant, once completed, is expected to connect 50% more households into national grid. Thus, this effort along with other projects will increase electrical power from 208 MW to 563 MW in 2024. Peat deposit is expected to generate 500 Megawatt electrical powers for 30 years. Although an effort was done to use peat as fuel, the power plant is still vulnerable to the lack of good quality of dry peat to operate and thus efforts are on to develop suitable technology for exploitation.

Identifying sites of high geoarchaeological potential using aerial LIDAR and GIS on Quadra Island, Canada

The dynamic environmental history and relative sea level (RSL) changes experienced on the Northwest Coast of North America during the early post-glacial period and the early Holocene resulted in significant archaeological visibility challenges for prospection of early coastal archaeological sites. This study offers an integrated methodological approach in support of locating palaeo-coastal sites by combining: (1) geomorphic interpretation of landscape attributes captured by LIDAR (Light Detection and Ranging) mapping; (2) GIS-based archaeological site potential mapping; and (3) local RSL history. The RSL history for the study site (Quadra Island, British Columbia, Canada) shows notable regression over the past 14,300 years from a highstand of at least 197 m resulting from post-glacial isostatic rebound. Late Pleistocene and early Holocene palaeo-shorelines are found inland from, and elevated above, modern sea level and represent key areas for archaeological prospecting. Bare-earth Digital Terrain Models (DTMs) derived from the LIDAR dataset were interpreted to identify palaeo-shorelines at 10 m and 30 m above mean sea level. A GIS-derived map was created to identify regions of high archaeological potential. Field validation suggests that this integrated methodology provides a promising approach for archaeological prospection that could be applied to other post-glacial coastal settings.

Nuclear ITS and AFLPs provide surprising implications for the taxonomy of Tephroseris longifolia agg. and the endemic status of T. longifolia subsp. moravica

The proportion of endemic taxa is a frequently used measure for assesment of biodiversity hotspots within the Carpathians. For confirming of an endemic status of a taxon, a thorough evaluation using modern tools of plant systematics is desirable. Tephroseris longifolia subsp. moravica has been considered to be a Western Carpathian endemic, but a previous study of morphological and genome size differentiation within the T. longifolia agg. showed that its endemic position is controversial. Therefore, in this study we aimed to detect genetic variability and evolutionary relationships within the T. longifolia agg. using nuclear ITS sequences and highly variable AFLPs on 38 populations covering the distribution range of the aggregate. Additionally, we analysed 22 populations of other putatively related species (T. aurantiaca, T. capitata, T. crispa, T. integrifolia and T. papposa). Genetic analyses proved that T. longifolia agg. is genetically well differentiated, but the results contradict the current taxonomic concept. Tephroseris longifolia aggregate, as defined here, comprises T. longifolia, T. crispa, T. pseudocrispa, T. tenuifolia and T. italica. Within T. longifolia, two subspecies can be recognised, namely T. l. subsp. longifolia and T. l. subsp. moravica. Furthermore, AFLPs confirm the close relationship of Pannonian and one Croatian populations to T. l. subsp. moravica. Therefore, we assume that T. l. subsp. moravica should not be considered a Western Carpathian endemic and most probably migrated to the Western Carpathian area during the post-glacial period.

Coupled stratigraphic and U-Pb zircon age constraints on the late Paleozoic icehouse-to-greenhouse turnover in south-central Gondwana

Abstract The demise of the Late Paleozoic Ice Age has been hypothesized as diachronous, occurring first in western South America and progressing eastward across Africa and culminating in Australia over an ∼60 m.y. period, suggesting tectonic forcing mechanisms that operate on time scales of 106 yr or longer. We test this diachronous deglaciation hypothesis for southwestern and south-central Gondwana with new single crystal U-Pb zircon chemical abrasion thermal ionizing mass spectrometry (CA-TIMS) ages from volcaniclastic deposits in the Paraná (Brazil) and Karoo (South Africa) Basins that span the terminal deglaciation through the early postglacial period. Intrabasinal stratigraphic correlations permitted by the new high-resolution radioisotope ages indicate that deglaciation across the S to SE Paraná Basin was synchronous, with glaciation constrained to the Carboniferous. Cross-basin correlation reveals two additional glacial-deglacial cycles in the Karoo Basin after the terminal deglaciation in the Paraná Basin. South African glaciations were penecontemporaneous (within U-Pb age uncertainties) with third-order sequence boundaries (i.e., inferred base-level falls) in the Paraná Basin. Synchroneity between early Permian glacial-deglacial events in southwestern to south-central Gondwana and pCO2 fluctuations suggest a primary CO2 control on ice thresholds. The occurrence of renewed glaciation in the Karoo Basin, after terminal deglaciation in the Paraná Basin, reflects the secondary influences of regional paleogeography, topography, and moisture sources.

Regeneration of Scots pine Pinus sylvestris L. in the Carpathians depends on site fertility

Abstract The aim of this work was to determine the biometric features of Scots pine Pinus sylvestris L. regeneration in terms of their susceptibility to weather-inflicted damage. We compared the damage between three sites located in the Polish part of the Carpathians: Scots pine planted in (I) fertile sites of mountain broadleaved and mixed broadleaved forest, (II) poor sites of mountain coniferous forest and (III) sites of Scots pine natural refuges during the post-glacial period. In each of the three sites of pine regeneration, 11 research plots were established with 50 pine trees on each plot. For each tree, the following biometric measurements were taken: diameter at breast height, height, 3-year height increment, crown length and crown width measured along the contour line. The Scots pine regeneration was found to vary in terms of their biometric features depending on the site fertility. In fertile sites, the biometric parameters of the trees increased at a faster rate compared to low-fertility sites causing an increase in their susceptibility to damage by adverse weather conditions such as snow and rime. Therefore, the silvicultural risk in fertile sites is high and thus the introduction of pine for regeneration should be avoided in fertile broadleaved and mixed broadleaved forests even if pine provenances from a mountain origin are to be planted. Furthermore, tending cuts in regeneration should be made frequently, but with moderate intensity so as to avoid excessive reductions in tree density. Intensive cuts, especially in fertile sites, promote the expansion of pine crowns, which further increases the risk of damage.

Genetic diversity hotspots and refugia identified by mapping multi-plant species haplotype diversity in China

Historical processes during the Quaternary are likely to have left a signature on the geographical distribution of intraspecific genetic variation. In particular, high genetic uniqueness could be expected within glacial refugia for multiple species. We aimed to test this for plants in China and whether multi-species hotspots of genetic diversity are good indicators of glacial refugia in this region. From chloroplast DNA haplotype data for 116 species we calculated two local genetic diversity metrics for each species: haplotype genetic richness and genetic uniqueness. From these two, only uniqueness could reliably identify refugia, whereas richness may indicate either glacial refugia or areas recolonized by genetic lineages from different refugia in the postglacial period. Our results suggest the occurrence of numerous cryptic refugia and their likely importance in the maintenance and evolution of the Chinese flora, and indicate that an approach that locates geographic hotspots of genetic diversity data can reliably identify refugia.

Spatial genetic structure of the endemic alpine plant Salix serpillifolia: genetic swamping on nunataks due to secondary colonization?

Pleistocene climatic changes affected the current distribution and genetic structure of alpine plants. Some refugial areas for the high elevation species have been proposed in the Alps, but whether they could survive on nunataks, is still controversial. Here, the spatial genetic structure in Salix serpillifolia revealed by chloroplast (cpSSR) and nuclear (nSSR) microsatellites was compared with the MaxEnt-modelled geographic distributions under current and past (Last Glacial Maximum) climate conditions. Our results suggest that the genetic pattern of differentiation detected in S. serpillifolia may be explained by the existence of Pleistocene refugia, including nunataks. The geographical patterns of variation obtained from the chloroplast and nuclear markers were not fully congruent. The spatial genetic structure that was based on nSSRs was more homogenous, while the cpSSR-based pattern pointed at strong genetic structure along the Alps. Five populations from the Central Alps had a combination of local and unique cpSSR clusters and admixture of those occurring in the Western and Eastern Alps. These findings may indicate the local survival of small populations of S. serpillifolia that were subsequently populated by new colonists in the postglacial period.

Phylogeography of Puumala orthohantavirus in Europe.

Puumala virus is an RNA virus hosted by the bank vole (Myodes glareolus) and is today present in most European countries. Whilst it is generally accepted that hantaviruses have been tightly co-evolving with their hosts, Puumala virus (PUUV) evolutionary history is still controversial and so far has not been studied at the whole European level. This study attempts to reconstruct the phylogeographical spread of modern PUUV throughout Europe during the last postglacial period in the light of an upgraded dataset of complete PUUV small (S) segment sequences and by using most recent computational approaches. Taking advantage of the knowledge on the past migrations of its host, we identified at least three potential independent dispersal routes of PUUV during postglacial recolonization of Europe by the bank vole. From the Alpe-Adrian region (Balkan, Austria, and Hungary) to Western European countries (Germany, France, Belgium, and Netherland), and South Scandinavia. From the vicinity of Carpathian Mountains to the Baltic countries and to Poland, Russia, and Finland. The dissemination towards Denmark and North Scandinavia is more hypothetical and probably involved several independent streams from south and north Fennoscandia.

Carbon Dioxide Emissions and Methane Flux from Forested Wetland Soils of the Great Dismal Swamp, USA

The Great Dismal Swamp, a freshwater forested peatland, has accumulated massive amounts of soil carbon since the postglacial period. Logging and draining have severely altered the hydrology and forest composition, leading to drier soils, accelerated oxidation, and vulnerability to disturbance. The once dominant Atlantic white cedar, cypress, and pocosin forest types are now fragmented, resulting in maple-gum forest communities replacing over half the remaining area. In order to determine the effect of environmental variabes on carbon emissions, this study observes 2 years of CO2 and CH4 soil flux, which will also help inform future management decisions. Soil emissions were measured using opaque, non-permanent chambers set into the soil. As soil moisture increased by 1 unit of soil moisture content, CH4 flux increased by 457 μg CH4–C/m2/h. As soil temperature increased by 1 °C, CO2 emissions increased by 5109 μg CO2–C/m2/h. The area of Atlantic white cedar in the study boundary has an average yearly flux of 8.6 metric tons (t) of carbon from CH4 and 3270 t of carbon from CO2; maple-gum has an average yearly flux of 923 t of carbon from CH4 and 59,843 t of carbon from CO2; pocosin has an average yearly flux of 431 t of carbon from CH4 and 15,899 t of carbon from CO2. Total Cha−1year−1 ranged from 1845 kg of Cha−1year−1 in maple-gum to 2024 kg Cha−1year−1 for Atlantic white cedar. These results show that soil carbon gas flux depends on soil moisture, temperature and forest type, which are affected by anthropogenic activities.

Ancient introgression drives adaptation to cooler and drier mountain habitats in a cypress species complex

Introgression may act as an important source of new genetic variation to facilitate the adaptation of organisms to new environments, yet how introgression might enable tree species to adapt to higher latitudes and elevations remains unclear. Applying whole-transcriptome sequencing and population genetic analyses, we present an example of ancient introgression from a cypress species (Cupressus gigantea) that occurs at higher latitude and elevation on the Qinghai-Tibet Plateau into a related species (C. duclouxiana), which has likely aided the latter species to extend its range by colonizing cooler and drier mountain habitats during postglacial periods. We show that 16 introgressed candidate adaptive loci could have played pivotal roles in response to diverse stresses experienced in a high-elevation environment. Our findings provide new insights into the evolutionary history of Qinghai-Tibet Plateau plants and the importance of introgression in the adaptation of species to climate change.

The submarine landscape of the ‘Jurassic Coast’ World Heritage Site, Dorset, UK and its Setting

This paper reviews recent studies of the seabed offshore from the Jurassic Coast and discusses their significance for understanding landforms of the World Heritage Site’s Setting as well as adding to understanding of the structures exposed in the cliffs. The processes of coastal formation as sea-levels rose and fell during the Pleistocene and in the recent post-glacial period are critical for this as they reveal the landforms which preserve former shorelines. Detailed surveys of the seabed provide evidence of the low slope of much of this seabed and so enhance the potential to interpret older terrestrial landforms which have been attributed to uplift of former sea beds. Considering both the seabed and the coast from the Pleistocene to the Anthropocene means that it is possible to assess the human impact on these landforms and processes, as well as the natural timescale within which changes occur. The paper describes the seabed geomorphology, relating this, where appropriate, to both the coastal landforms and the exposed structures. Current interpretations of the seabed features and their implications for our understanding of the recent evolution of the Site and Setting are explored. The features of the coast and adjacent sea bed at different phases of the changing coastal environment are discussed to the extent that the available evidence makes this possible, but for much of the area this remains speculative.

Paraglacial history and structure of the Moosfluh Landslide (1850–2016), Switzerland

Rock slopes next to the tongue of the Great Aletsch Glacier, Switzerland are characterized by rapid environmental adjustment to non-glacial conditions. This study investigates and describes in detail the historic development of the largest rock slope instability in this area, called Moosfluh Landslide. We study in detail the structure, evolution and stability since the end of the Little Ice Age (LIA) until September 2016 and discuss their relationships with the evolution of the Great Aletsch Glacier since the Lateglacial period. In 2016 around 50 m of glacial ice thickness were left at the Moosfluh Landslide toe, where in 1850 glacial ice was >400 m thick. The changing stability conditions at the interface with the melting valley glacier are studied based on novel balanced cross sections and kinematic model of the Moosfluh Landslide dominated by toppling phenomena in metamorphic rock. The morphology and evolution of this landslide since the LIA are investigated with multi-temporal landslide maps based on aerial digital photogrammetry (ADP) applied to historic images since 1961. Internal deformation at Moosfluh is accommodated by shear slip along uphill-facing foliation and fault planes, and by extensional faulting forming tension cracks and graben-structures at the landslide head. Together with Digital Image Correlation (DIC) and total station monitoring (TPS) the Moosfluh Landslide displacement history was reconstructed, evidencing post-Egesen landslide displacements and an acceleration of movements since the LIA and especially since 2007. The displacement rates increase from few mm per year until the nineties to several meter per day in September 2016. Different kinematic models have been tested and changes in the Moosfluh rock slope stability in response to retreating glacial ice and changing groundwater conditions was explored with limit-equilibrium analysis of the stepped planar block toppling model of Goodman and Bray (1976). For the observed conditions and a toppling joint friction angle of 19° the simulated factor of safety drops non-linearly from the LIA maximum (1.12) to the year 2007 (1.02), when the height of ice above the valley bottom melted down to 100 m.This study illustrates with unprecedented detail the time scales, displacement magnitudes and structural evolutions of a large toppling mode slope instability in a paraglacial setting. The long-term cumulative slope displacements between the Egesen stadial and the LIA are of the same magnitude as the cumulative displacements between the LIA and the year 2016. As large portions of the studied slope underwent multiple retreats and advances of the Great Aletsch Glacier during the Lateglacial and Postglacial period, the observed onset of large slope displacements should be related to incremental damage (slip weakening and weathering) occurring along steeply dipping toppling fractures during the LIA.