Postglacial Period Research Articles

Fires and their Significance in the Earth’s Post-Glacial Period: a Review of Methods, Achievements, Groundwork

Fires and their Significance in the Earth’s Post-Glacial Period: a Review of Methods, Achievements, Groundwork

Postglacial Fire and Vegetation History from Doheney Lake in the Sinlahekin Wildlife Area, Okanogan County, Washington

In recent decades, dry ponderosa pine (Pinus ponderosa)-dominated forests of the eastern Cascades have experienced a dramatic increase in large, high-severity wildfires resulting in significant damage to natural resources. However, relatively little is known about long-term trends in postglacial fire activity in these forests. The purpose of this study was to reconstruct the fire and vegetation history of the Doheney Lake watershed, located in north-central Washington, using macroscopic charcoal and pollen analysis of a ca. 12,330-year-long lake sediment record. The results illustrate that regional climatic change, as well as climatically-controlled vegetation shifts, were the primary drivers of fire activity during much of the postglacial period. In particular, the establishment of the modern forest between ca. 7500 and 6000 cal yr BP due to cooler and moister conditions led to greater amounts of burnable biomass and generally higher levels of fire activity. The study results also suggest that greater interannual climate variability linked to drought may have played a role in the highly variable fire activity during much of the past 6,000 years. Additionally, it is likely that Indigenous cultural burning contributed to the fire activity at the site prior to Euro-American settlement, in particular during the past 4,000 years. Since ca. 125 cal yr BP (1825 CE), an almost complete absence of fire has allowed for the encroachment of shade-tolerant trees and has resulted in the potential for catastrophic wildfire, like that experienced at the site in 2015.

The origin and dispersal of Firmiana danxiaensis among isolated specific landscapes

AbstractChina has the most numerous Danxia and Karst landscapes, which serve as special terrestrial islands harboring ample endemic species, though how did these endemic species spread among those isolated sites is still an unresolved issue. To address this question, we explored the phylogeographical structure and demographic history of Firmiana danxiaensis, a tree species endemic to Danxia and Karst landscapes. We collected 295 samples (28 populations) of F. danxiaensis. Plastid genomes were assembled for 25 representative samples. Sanger sequencing of four plastid regions and restriction‐site‐associated DNA sequencing were performed on the 28 populations. The phylogenetic tree constructed from plastid genomes and restriction site‐associated DNA sequencing (RAD‐seq) data supported that F. danxiaensis originated from Mount Danxia and Nanxiong Basin, spread to Karst landscapes near Yingde City, and then back to Danxia Mountain and the Nanxiong Basin. In the Nanxiong Basin, the latter arrivals captured the plastid of the former. Population analyses revealed strong population structure among and within Danxia and Karst landscapes, possibly due to low seed and pollen dispersal abilities of the species. The demographic and ecological niche modeling approaches suggested that F. danxiaensis have widely occurred in the southeast of China during the last glacial period, and later retreated to the cliffs of Danxia and Karst landscapes due to temperature rising and competition failure. The declining of the effective population size of the species throughout the postglacial period suggested that global warming, agriculture, and industrial civilizations could have affected the survival of this species, and more measures should be taken to conserve these species.

Geo-archaeology and Haíɫzaqv oral history: Long-term human investment and resource use at EkTb-9, Triquet Island, N̓úláw̓itxˇv Tribal Area, Central Coast, British Columbia, Canada

Archaeological site EkTb-9 is located on Triquet Island in the N̓úláw̓itxˇv Tribal area of Haíɫzaqv (Heiltsuk) Nation territory, on the Central Coast of British Columbia, Canada. The results of radiometric dating and the analysis of palaeoenvironmental correlates indicate that the site was a persistent place of repeated human occupation spanning the early post-glacial period to the present day. This paper focuses on the paleogeographic and geomorphic setting of EkTb-9. Stratigraphic records show a complex array of site formation processes. Marine beach sediments are elevated above modern sea level, an extensive sand sheet consistent with a possible palaeotsunami event is present, as well as organic soils and peat deposits. Cultural strata are interbedded with these and include both shell-less and preserved shell accumulations. Results from our geo-archaeological and palaeoenvironmental assessments indicate that the outer coastal island changed from what was likely an open landscape during the early post-glacial period to the hypermaritime coastal temperate rainforest environs of the present day. Our interpretations are combined with Haíɫzaqv oral history and discussions are organized by Haíɫzaqv temporal phases identified for the N̓úláw̓itxˇv Tribal area. Combining Indigenous knowledge with our archaeological interpretations enhances our collective understanding of the long-term record of human occupation and investment at EkTb-9.

An assessment of potential causal links between deglaciation and eruption rates at arc volcanoes

One of the fundamental questions that underpins studies of the interactions between the cryosphere and volcanism is: do causal relationships exist between the ice volume on a volcano and its eruption rate? In particular, it is critical to determine whether the decompression of crustal magma systems via deglaciation has resulted in enhanced eruption rates along volcanic arcs in the middle to high latitudes. Evidence for such a feedback mechanism would indicate that ongoing glacier retreat could lead to future increases in eruptive activity. Archives of eruption frequency, size, and style, which can be used to test whether magma generation and eruption dynamics have been affected by local ice volume fluctuations, exist in the preserved eruptive products of Pleistocene-Holocene volcanoes. For this contribution, we have reviewed time-volume-composition trends for 33 volcanoes and volcanic groups in arc settings affected by glaciation, based on published radiometric ages and erupted volumes and/or compositions of edifice-forming products. Of the 33 volcanic systems examined that have geochronological and volumetric data of sufficient resolution to compare to climatic changes since ∼250 ka, increases in apparent eruption rates during post-glacial periods were identified for 4, with unclear trends identified for a further 12. Limitations in the geochronological and eruption volume datasets of the case studies make it difficult to test whether apparent eruption rates are correlated with ice coverage. Major caveats are: 1) the potential for biased preservation and exposure of eruptive materials within certain periods of a volcano’s lifespan; 2) the relative imprecision of geochronological constraints for volcanic products when compared with high-resolution climate proxy records; 3) the reliance on data only from immediately before and after the Last Glacial Termination (∼18 ka), which are rarely compared with trends throughout the Pleistocene to test the reproducibility of eruptive patterns; and 4) the lack of consideration that eruption rates and magma compositions may be influenced by mantle and crustal processes that operate independently of glacial advance/retreat. Addressing these limitations will lead to improvements in the fields of geochronology, paleoclimatology, and eruption forecasting, which could make valuable contributions to the endeavours of mitigating future climate change and volcanic hazards.

Depositional history of the subaqueous delta off the southeastern coast of Korea during the post-glacial period

The distal mud deposit (DMD) of the Korea Strait Shelf, located along the southeastern coast of Korea and detached from the main sediment source, the mouth of the Nakdong River, is considered a subaqueous delta system. The complex spatiotemporal changes in the stratigraphic architecture of the DMD were reconstructed, based on combined seismic and sediment core data, according to the three stages of post-glacial sea-level rise. During the early transgressive stage (from ca. 19 to 10.9 ka), transgression occurred at a relatively deeper northern outer shelf of the DMD, where Unit A began to be deposited in an aggradational stratal stacking pattern. During the late transgressive stage (ca. 10.9 to 8 ka), further sea-level rise provided sufficient accommodation for DMD, but an insufficient sediment supply from the Nakdong River might have prevented sedimentation. At the highstand stage (ca. 8 ka to the present), the increased supply of suspended sediments from the Nakdong River coupled with the entrance of the Tsushima Warm Current through the Korea Strait may have enabled the along-shore lobate progradation of Unit B on the flat and wide southern shelf. After appoximately 2 ka, as Unit B proceeded into the narrow, steep northern shelf, it started to prograde in a shore-normal direction, controlled by a rapid downslope decrease in near-bed shear stress. Over the last 700 years, sediments have been actively deposited at the depocenter of the DMD by frequent storm surges during the summer season. The reconstructed depositional history of the DMD demonstrates the importance of the pre-existing shelf morphology, along-shore currents, and storm surges in offshore sediment transport for a subaqueous delta in a microtidal shelf with a relatively small riverine sediment load.

Evidence of large-scale absence of frozen ground and gas hydrates in the northern part of the East Siberian Arctic shelf (Laptev and East Siberian seas)

This study investigated the zones associated with the potential distribution and absence of frozen ground and gas hydrates on the East Siberian Arctic Shelf in the Laptev and East Siberian seas. The investigation was based on an analysis of velocities of refracted waves registered as first breaks from common-shot gathers along 71 common depth point seismic lines with a total length of 15 630 km acquired by JSC MAGE in 2007–2016. Consequently, essentially new data that illustrate the state of the cryolithozone on the East Siberian Arctic Shelf were obtained. In particular, this study confirmed a significant decrease in the area of possible existence of frozen ground and methane hydrates in the postglacial period. Based on an extensive analysis of subsea frozen ground degradation zones on the shelves of the Laptev, East Siberian, Chukchi, and Beaufort seas (∼57% of the total area), it can be concluded that there is a low probability of considerable contribution of methane, being released from the dissociating gas hydrates, to climate change.

The anthropogenic effect of land use on population genetics of Malcus inconspicuus.

Since the beginning of the Holocene era, human activities have seriously impacted animal habitats and vegetative environments. Species that are dependent on natural habitats or with narrow niches might be more severely affected by habitat changes. Malcus inconspicuus is distributed in subtropical China and highly dependent on the mountain environment. Our study investigated the role of the mountainous landscape in the historical evolution of M. inconspicuus and the impact of Holocene human activities on it. A phylogeographical approach was implemented with integrative datasets including double-digest restriction site-associated DNA (ddRAD), mitochondrial data, and distribution data. Three obvious clades and an east-west phylogeographical pattern were found in subtropical China. Mountainous landscape has "multifaceted" effects on the evolutionary history of M. inconspicuus, it has contributed to population differentiation, provided glacial refuges, and provided population expansion corridors during the postglacial period. The effective population size (Ne) of M. inconspicuus showed a sharp decline during the Holocene era, which revealed a significantly negative correlation with the development of cropland in a hilly area at the same time and space. It supported that the species which are highly dependent on natural habitats might undergo greater impact when the habitat was damaged by agricultural activities and we should pay more attention to them, especially in the land development of their distribution areas.

Recent and Past Arboreal Change: Observational and Retrospective Studies Within a Subalpine, Birch-Dominated (Betula Pubescens Ssp. Czerepanovii) Mountain Valley in the Southern Swedish Scandes-Responses to Climate Change and Land Use

Multi-scale observations and reconstructions of treeline and associated plant cover changes are reviewed in this study. The main focus is on the dynamics of the treeline ecotone within a mountain valley in the southern Swedish Scandes. This area is well-researched for more than 100 years, with a background of historical studies covering the entire Holocene epoch. Trees were present on ice-free nunataks already during the Late-Glacial, 17 000-13 000 cal. a BP. Mountain birch (Betula pubescens ssp. czerepanovii), Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) then grew 400-700 m higher than their current treelines, indicative of summer temperatures 3 °C higher than present. In addition, the tree flora contained Siberian larch (Larix sibirica) and broad-leaf thermophilic and deciduous species, Quercus robur, Corylus avellana, Ulmus glabra and Alnus glutinosa. Eventually, the climate turned cooler, particularly enhanced around 5000 cal. a BP. This course of change initiated the Neoglacial period, when thermophilic species were extirpated. Concomitantly, mountain birch forest and spruce benefitted from this course of change. Pine, on the other hand was disfavored and regressed in the treeline elevation and general abundance on the landscape. These trends continued until the Mediaeval period AD 1000-1300, when temperature raised above present-day standards and the pine treeline locally shifted upslope by at least 100 m. This favourable epoch was discontinued quite abruptly by resurgence of Neoglacial cooling; the “Little Ice Age”, which prevailed until the late 19th century. Widespread glacier expansion, high-elevation arboreal decline and treeline retraction then occurred. With a gentle onset in the late 19th century or somewhat earlier, a modern and still prevailing warming period was accentuated by the late 1930s. Subsequently, slight cooling prevailed for 3-4 decades, whereupon warming was resumed with short interruptions until the present day. One distinct short-term cooling-conditioned setback occurred during the 1980s. Transient permafrost formed close to the treeline, and locally some treeline recession took place. Thereafter, warming has re-occurred and glaciers and permafrost have receded. Treeline rise and densification of the treeline ecotone are once again active processes in the mountainscape. Currently, most conspicuous is a process of pine reclamation of local ground lost during the Little Ice Age. Hereabouts, seed regeneration, still virtually without winter injuries, is taking place at an unprecedented rate and abundance. Mountain birch is gaining ground in snow rich depressions in the birch belt and is currently regressing in exposed and snow-poor sections of the local topography. Current biotic changes within the treeline ecotone are well within the ranges of inferred natural variabilty during the postglacial period.

The LGM refugia of deciduous oak and distribution development since the LGM in China

The distribution development of oak has significant effects on ecosystems and society. Long-term forest distribution studies can help to better understand the vegetation dynamics under climate change or human activities in the future. In this study, we integrated different methods (i.e., palaeoecology, phylogeography, and species distribution models) to investigate the likely locations of glacial refugia and the postglacial development of the main deciduous oak species (i.e., Quercus variabilis, Q. mongolica, Q. dentata, Q. aliena, Q. acutissima and Q. liaotungensis). The results indicated that mountains such as the Changbai, Qinling, and Dabie Mountains acted as the refugia in northern and central China during the Last Glacial Maximum (LGM). The present Quercus in northern China could be the result of local dispersal during the postglacial period rather than only that of long-distance migration from south to north. Climate was the main influencing factor for oak migration, while human activities did not show much influence on this widespread genus. The topography acted as a buffer and made the mountains to act as refugia under a deteriorated climate. Compared with other main tree genera (e.g., Pinus and Betula), the refugia locations and migration routes of deciduous oak species were different because of their physiological differences. The individual migration dynamics of these three genera need to be considered when modelling their dynamics.

Possible links with methane seepage and gas hydrate dynamics inferred from authigenic barite records in the northern south china sea

Numerous methane seepage events occurred in periods of low or falling sea level since 330 ka BP, which is attributed to decrease in hydrostatic pressure and subsequent gas hydrate dissociation in the northern South China Sea (SCS). The seepage intensity likely decrease due to gas hydrate stabilization once there was a relatively high-stand sea level. However, there are few geochemical records of decline in upward methane flux in the northern South China Sea. Here, combing porewater and solid-phase analyses, the geochemical cycling of barium was investigated in two piston cores from sites HD109 and HD319 within two areas with inferred gas hydrate occurrence in the Taixinan Basin of the northern SCS, in order to track the net decrease in the upward methane flux and to estimate the total duration time of these events in the studied sediments. The results indicate that there are four intervals with barium enrichments in the sediment section overlying the occurrent sulfate-methane transition zone (SMTZ) at both cores, suggesting the SMTZs have downward migrated through time. Based on the excess barium contents and the diffusive Ba2+ fluxes above the current SMTZ, we estimate the total time for barium accumulation at both cores is about ten thousand years. It is suggested that some methane seepage events temporarily enhance the upward flux of methane, inducing anaerobic oxidation of methane and associated SMTZ close to the sediment surface before the Holocene. After the most intensive seepage event ceased in the post-glacial period, the upward methane flux decreased and the SMTZ migrated downward gradually, preserving enrichments of diagenetic barite. Overall, these new data confirm the episodic decrease in upward methane flux recorded by authigenic barite after the last glacial maximum, which is likely related to the stabilization of underlying gas hydrate reservoir. This study may fill in the gap of the geochemical records of the variations in methane seepage and gas hydrate system during the post-glacial period in the northern SCS.

Dynamic sulfur and carbon cycles related to microbial sulfate reduction and volcanic activity during the Hirnantian glaciation in the Upper Yangtze Basin, South China

Parallel positive excursions of organic carbon (δ13Corg) and pyrite sulfur (δ34Spy) isotopes occurred globally during the Hirnantian glacial period. However, the reasons for these isotope excursions and their relationship with paleoenvironmental dynamics are not fully understood. This study presents a high-resolution geochemical investigation of the Tianlin section of the Upper Yangtze Basin, South China. The total organic carbon (TOC), iron speciation, trace elements, δ13Corg, and δ34Spy were analyzed and compared with published results from the other four sections in the same basin. A negative relationship was observed for the sulfate reduction index (SRI) with TOC and organic carbon accumulation rate. This suggests that the abundance of sedimentary organic matter was not the main factor inhibiting microbial sulfate reduction (MSR). The significant positive correlations of SRI with pyrite and δ34Spy showed that MSR promoted the formation of pyrite and that the availability of sulfate was the main limiting factor for the δ34Spy change. The negative excursions of δ13Corg and δ34Spy during the pre-glacial and post-glacial periods were coupled with dense segments of bentonite, indicating that volcanism was the main driving force for the negative excursions of C and S isotopes. Moreover, the sulfate input of rivers, restored at the post-glacial period, was the main reason for the continued negative excursion of S isotopes. Our results emphasize the key role of MSR and volcanic activity in C and S isotope excursions and their corresponding environmental changes in semi-restricted basins during the Hirnantian glaciation.

Morphotectonics, Seismicity, and Exogenous Processes of the Kola Peninsula

Abstract—The purpose of this study is to determine a morphologically pronounced fault–block structure identified with the neotectonic stage and compare it with sites with manifested exogenous processes, as well as modern and historical paleoseismicity in order to establish faults activated in the postglacial time. Based on the analysis of space images (Landsat-ETM+) and a digital elevation model (GTOPO-30), the territory of the Kola Peninsula and the adjacent part of North Karelia is subjected to morphostructural interpretation with identifying morpholineaments and an elementary block structure. It is shown by the analyzing the directions and extent of elementary, single (simple), and complex (echeloned, parallel conjugated, and imbricated) linear structures and their zones that both linear (fault) and areal (block) structures are characterized by a predominance of a single system of northwestern and northeastern differences with a clear dominance of the former and unimodal distribution of the extent of faults and the area of blocks, depending on their number. This indicates a single (recent) stage in the formation of the morphotectonic appearance of the territory and no discrete hierarchy of the morphostructures. The degree of fragmentation of the territory at different depths is calculated depending on the number and extent of morpholineaments. It is determined that morpholineaments have a high degree of inheritance from Archean–Proterozoic structures (≈50%). Elementary morphotectonic blocks are grouped into composite blocks bounded by linear zones of great extent (100–600 km) having individual physiognomic features determined by fault patterns, which indicates the nature of the neotectonic dynamics and the degree of inheritance or reformation of the structural plan. The localization of manifestations of exogenous processes, epicenters of paleo-, historical, and modern earthquakes is determined on the basis of the analysis of topographic maps scaled at 1:100,000, catalogs of historical and paleoearthquakes, and the consolidated literature (including the data obtained by the authors of this study) on paleoseismic deformations. A geoinformation base is compiled, which is used to simulate the spatial distribution of endo- and exogenous signs of tectonic activity and compare it with the neotectonic fault–block structure. The spatial similarity of endogenous and exogenous activation zones and their confinement to faults, defined as activated in the postglacial time, are revealed. It is revealed that the following elements are most active in the postglacial–Holocene. First, flank elements on the Kola Peninsula along the Barents Sea coast, the Kandalaksha Bay shores, and the Gorlo Strait of the White Sea. Second, the central (nodal) part with the Khibiny and Lovozero massifs. Third, submeridional (transverse) secant structures separating the eastern part of the peninsula from the western part (Khibiny–Kola and Khibiny–Niva). The spatial parameters of the activated zones indicate a range of earthquake magnitudes M ≈ 6.5–7.5 generated by these structures both in the postglacial period and in the Neopleistocene as a whole.

독도 서도 남동해안의 애추 지형발달

Taluses are usually developed at the boundary between slope and gravel beach in the Southeast Coast of Seodo, Dokdo. The largest one is about 50m long. Some valleys on a thick tuff layer are dissected by streams, because tuff is less resistant than trachyandesite to erosion in this coast. Therefore, a plenty of debris are supplied from these valleys. In this slope, we established three study transects (A, B, and C). The lower portion of these taluses is not dissected by wave erosion. It is related to the shallow strait about 2m depth between Dongdo and Seodo, because wave sediments delivered from offshore continuously fill the strait. The typical landscape of the taluses in the study area is presumed to have been shaped by geomorphic processes during the Quaternary. That is, the bottom of the talus is composed primarily of the debris originating from the glacial period, some of which are covered with the sediments delivered from the surrounding valleys during the postglacial period. The main factors that affectedthe development of these taluses are considered as follows; bedrock characteristics of the slope, density of lineaments, slope gradient, vegetation cover, and soil distribution.

Overview of the fish fauna of the Chaunskaya basin – the area of the natural reserve "Chaunskaya Guba" and the port of Pevek (East Siberian Arctic)

The fishes of the Chaunskaya Bay and its Basin have been little studied. Part of the coast of this vast Arctic estuary (about 9 thousand km2) is included in the state nature reserve “Chaunskaya Guba”; at the entrance to the bay there is the seaport of Pevek, a transit hub of the Northern Sea Route. The area has been identified as one of the priorities for the protection of biodiversity in the seas of the Russian Arctic. Solving the problem of biota conservation begins with an inventory of the fauna. The paper presents the results of summarizing data on the species composition of marine, anadromous and freshwater fishes in the Chaunskaya Bay and its basin. The updated list includes 36 species of 28 genera, 16 families and 10 orders. In marine waters there are 31 species (18 marine, 13 anadromous and semi-anadromous fish), in rivers and lakes there are 5 freshwater (and 13 anadromous and semi-anadromous) species. The Muksun Coregonus muksun (Pallas, 1814) and the pike Esox lucius Linnaeus, 1758, which were absent in the fauna lists, are added. The lamprey Lethenteron kessleri (Anikin, 1905), the Pacific herring Clupea pallasii Valenciennes, 1847, and the Arctic charr Salvelinus alpinus (Linnaeus, 1758), which were previously recorded, are not confirmed by reliable findings. The marine fish community of the Chaunskaya Bay is an impoverished shelf fauna of the East Siberian Sea and includes species adapted to desalination. The freshwater ichthyofauna of the basin differs from the fauna of the neighboring Kolyma River region in the loss of a number of freshwater species, which are believed to have been extinct because of the Holocene cooling. A significant part of the fish complex consists of elements of the North Pacific fauna that spread to the East Siberian Sea in the postglacial period.

Little Ice Age abruptly triggered by intrusion of Atlantic waters into the Nordic Seas.

The Little Ice Age (LIA) was one of the coldest periods of the postglacial period in the Northern Hemisphere. Although there is increasing evidence that this time interval was associated with weakening of the subpolar gyre (SPG), the sequence of events that led to its weakened state has yet to be explained. Here, we show that the LIA was preceded by an exceptional intrusion of warm Atlantic water into the Nordic Seas in the late 1300s. The intrusion was a consequence of persistent atmospheric blocking over the North Atlantic, linked to unusually high solar activity. The warmer water led to the breakup of sea ice and calving of tidewater glaciers; weakening of the blocking anomaly in the late 1300s allowed the large volume of ice that had accumulated to be exported into the North Atlantic. This led to a weakening of the SPG, setting the stage for the subsequent LIA.

Next-generation phylogeography resolves post-glacial colonization patterns in a widespread carnivore, the red fox (Vulpes vulpes), in Europe.

Carnivores tend to exhibit a lack of (or less pronounced) genetic structure at continental scales in both a geographic and temporal sense and this can confound the identification of post-glacial colonization patterns in this group. In this study we used genome-wide data (using genotyping by sequencing [GBS]) to reconstruct the phylogeographic history of a widespread carnivore, the red fox (Vulpes vulpes), by investigating broad-scale patterns of genomic variation, differentiation and admixture amongst contemporary populations in Europe. Using 15,003single nucleotide polymorphisms (SNPs) from 524 individuals allowed us to identify the importance of refugial regions for the red fox in terms of endemism (e.g., Iberia). In addition, we tested multiple post-glacial recolonization scenarios of previously glaciated regions during the Last Glacial Maximum using an Approximate Bayesian Computation (ABC) approach that were unresolved from previous studies. This allowed us to identify the role of admixture from multiple source population post-Younger Dryas in the case of Scandinavia and ancient land-bridges in the colonization of the British Isles. A natural colonization of Ireland was deemed more likely than an ancient human-mediated introduction as has previously been proposed and potentially points to a larger mammalian community on the island in the early post-glacial period. Using genome-wide data has allowed us to tease apart broad-scale patterns of structure and diversity in a widespread carnivore in Europe that was not evident from using more limited marker sets and provides a foundation for next-generation phylogeographic studies in other non-model species.

Relict populations of Lyonetia ledi Wocke, 1859 (Lepidoptera, Lyonetiidae) from the Alps indicate postglacial host-plant shift to the famous Alpenrose (Rhododendron ferrugineum L.)

Lyonetia lediWocke, 1859 (Lyonetiidae), was hitherto considered as a boreal species with a circumpolar distribution pattern and relict populations in isolated peat bogs north-east of the Alps (Austria, Czech Republic, Germany). In Europe it is known as a leaf-miner onRhododendron tomentosumStokes ex Harmaja (Ericaceae) as the primary host-plant and alsoMyrica galeL. (Myricaceae). The first record ofL. ledifrom the Swiss Alps onRhododendron ferrugineumL., the famous Alpenrose, indicates an ancient host-plant switch during postglacial periods whenR. tomentosumandR. ferrugineumshared habitat in the prealps. Conspecificity with northern populations is supported by the adult morphology and supplementing DNA barcodes (mtDNA COI gene).L. lediis the first obligatory leaf-mining species onR. ferrugineum. Details of the life-history and habitat are described and figured. The record finally substantiates the probability of an autochthonous population in Carinthia (Austria), from where the species was recently published as new to the Alps.

Karst caves in Haida Gwaii: Archaeology and paleontology at the Pleistocene-Holocene transition

Karst cave investigations in the south of Haida Gwaii have opened a small window on human and paleontological components of the early post-glacial landscape. At three cave locations (K1, Gaadu Din 1 and Gaadu Din 2) our investigations recovered a paleontological record extending from ca. 13,400 to 11,000 years ago and a small number of human artifacts dating from ca. 12,600 to 11,000 years ago. The animal bones recovered are dominated by black and brown bear remains, revealing that these caves were being used for winter dens. Other species present include deer, caribou, and salmon. Domestic dog remains with a direct radiocarbon age of 13,100 years ago are the earliest indicator of human presence from the cave assemblages, and are also the earliest known domestic dog remains reported on in the Americas. Brown bear and deer disappear from the paleontological record at the end of the Pleistocene, but other species persist into the Holocene, most of which continue to thrive on the islands to this day, with the exception of caribou which were extirpated in the early 20th Century. The stone tools that we found are predominately spearpoints and fragments thereof, which were used to hunt denning bears. Additional stone tool types from the Gaadu Din Caves reveal that they were occasionally used by humans as temporary shelters. As sea level was lower than today between 13,400 and 11,000 years ago, the caves provide an alternative target for late Pleistocene archaeological prospection that does not involve subtidal work. Our research demonstrates that karst caves on Haida Gwaii provided ecological and cultural focal points during the early post-glacial period. These caves remained sufficiently stable to preserve the residues of activities including bear denning and bear hunting. With the commencement of the Holocene, the record of animal and human use of the three caves diminishes.

Identification of Atlantic water inflow on the north Svalbard shelf during the Holocene

ABSTRACTNordaustlandet is located in the northeastern part of the Svalbard archipelago, within the northernmost reach of the West Spitsbergen Current. This current transports Atlantic water to the Arctic Ocean along the western and northern Svalbard margins. This region is well‐suited for reconstructing the history of changing Atlantic water inflow to the Arctic Ocean. We studied the marine sediment core HH12‐04‐GC from Rijpfjorden. Benthic foraminiferal assemblages and sedimentological data are combined to reconstruct the palaeoenvironment of the fjord from the end of the last local deglaciation to the late Holocene. The local deglaciation, between 11.3 and 10.6 cal ka bp, was dominated by active glacier calving processes, associated with a strong inflow of Atlantic water. This led to the establishment of glaciomarine conditions. The Holocene was initially characterised by a relatively stable and warm environment associated with a strong contribution of Atlantic water. Glaciomarine influence progressively decreases after 9.7 cal ka bp and the Atlantic water contribution increases. The late Holocene displayed a similar environment to today, with the influence of glaciomarine conditions and limited Atlantic water inflow. These results confirm that Atlantic water inflows made a continuous contribution to northern Nordaustlandet throughout the postglacial period.