Glacio-isostatic Uplift Research Articles

Paleoproterozoic (Huronian) valley-controlled deglacial-fluvial sedimentation, northern Cobalt Basin, Ontario, Canada

Detailed sedimentological and stratigraphic analysis of pre-vegetation sedimentary systems that deposited across global-scale climate change episodes is key to fully understanding past feedback responses in Earth surface systems and the details of their paleoenvironments. The Cobalt Basin, recording the upper Huronian Supergroup, captures a transition from glacial (Gowganda Formation) to post-glacial (Lorrain Formation) deposystems in parallel with Earth's Great Oxidation Event and is ideal for sedimentological/stratigraphic analysis due to its limited post-depositional deformation. Stratigraphic measurements and correlations from the northern Cobalt Basin reveal that the Gowganda and Lorrain formations are preserved within a paleovalley, interpreted as a fjord. Sub-glacial deposits of the Coleman Member (lower Gowganda Formation) are preserved at the base of the paleovalley, unconformably above Archean volcanic and granitic rocks of the Abitibi subprovince. Subsequently, the fjord was filled by glaciomarine strata sourced from a grounded tidewater icesheet prior to climate warming. Above the glaciomarine deposits, deltaic deposits of the Firstbrook Member (upper Gowganda Formation) represent a transition to nonglaciogenic deposition under a warm and humid climate. The deltaic deposits comprise three facies associations: (1) delta front/slope strata dominated by horizontally stratified siltstone; (2) interdistributary bay deposits composed of symmetrically rippled and thinly laminated siltstone; (3) distributary mouth bar deposits dominated by very fine-grained arenite. Delta front/slope deposits occur directly above glaciomarine strata, while interdistributary bay and distributary mouth bar deposits occur above delta front/slope strata and are laterally discontinuous across the study area. Prodelta deposits are not preserved in the study area, although they are reported elsewhere in the basin. At the flanks of the paleovalley, alluvial fan deposits, confined by Archean rocks, interfinger with deltaic strata. Alluvial fan sedimentation, triggered by enhanced weathering in an unvegetated warm and humid setting, led to flashy sheetflood deposition due to significant topographic variations at the flanks of the valley setting. In some instances, sandstone beds of the overlying Lorrain Formation, comparable to distal to medial reaches of the modern South Saskatchewan River, cut down through delta strata. Up-section, the braidplain strata coarsen to gravel-rich facies representing Donjek River-type deposits. Overall, the stratigraphic succession in the northern Cobalt basin study area represents a single progradation from glaciomarine through deltaic deposition, into fluvial braidplain deposition. The succession is preserved at the cratonward limit of a passive margin, suggesting that progradation was likely influenced by relative sea-level fall linked to glacio-isostatic uplift, similar to fjord-filled sedimentary successions that have developed since the Last (Pleistocene) Glacial Period.

Reconstruction of wetland development across a postglacial chronosequence based on palynomorph and carbon/nitrogen modern analogues

Postglacial isostatic uplift causes rapid land emergence and drives wetland development on Canada's James Bay providing a modern field laboratory to test models of wetland succession. In this study, we reconstruct wetland development in four Holocene sediment/peat records ranging in age from 6500 to 250 years based on a suite of palynomorph (pollen, spores, and dinoflagellate cysts) and carbon/nitrogen modern analogues from tidal marshes, fens, and bogs of eastern James Bay. The fossil palynomorph data was compared to the modern palynomorph signatures using Discriminant Analysis and a similarity measure (squared chord distance). Principal Components Analysis (PCA) was used to determine if gradients exist among samples from different ecosystems and which taxa are most important in defining these gradients. Palynological richness (rarefaction analysis) and evenness were used to explore the palynological diversity of various paleo-wetland types. Our results indicate that while wetland development generally progressed from nutrient-rich to nutrient-poor and/or ombrotrophic communities, the succession was reset at times and reversals occurred. Our study revealed that modern wetlands of James Bay are generally good analogues for their mid to late Holocene counterparts, although rapid glacio-isostatic uplift during the mid Holocene favored the formation of poor analogue, transitional tidal communities that were palynologically heterogenous and occasionally diverse. Inter-site comparisons suggest that a combination of autogenic processes and allogenic forcing have contributed to Holocene wetland development in eastern James Bay, the latter including factors such as changes in surface hydrology, fire, and climate.

Late Glacial and Holocene shore-level changes in the Aarhus Bugt area, Denmark

We propose a new relative shore-level curve for the Aarhus Bugt area, an embayment in eastern Jylland, Denmark, based on a compilation of published and new radiocarbon ages of organic material. Lakes existed in the area during the Late Glacial and Early Holocene. Lake level rose gradually until the region was inundated by the sea at c. 9000 cal. years BP. The relative sea level reached a high stand at about 6000 cal. years BP, when the local relative sea level was c. 3 m above present-day mean sea level. The Aarhus Bugt area was inundated by the sea later than the Limfjord area in northern Jylland, but earlier than the Lillebælt region in southern Denmark. The shore-level curves for these areas differ partly because the glacio-isostatic uplift was more pronounced in the Limfjord area than farther south and partly because the northern regions were inundated by the sea earlier than the southern areas.

Paleogeographic reconstructions of the Northwest Karelia region evolution in the holocene based on the study of small lake sediments

The results of a study of bottom sediments from two small nameless lakes located on the proximal side of Salpausselkä II (Kalevala) glacial deposits at various elevations within glacial-lacustrine and morainic plains are reported. Using a set of methods, including spore-pollen, diatom and radiocarbon (C14) analyses, new data were obtained on the onset of the formation of the lakes, stages of their development, sedimentation of organic sediments and the effect of local geomorphological conditions on the composition of spore-pollen spectra and diatom complexes in different paleoclimatic periods in the Holocene. Evidence shows that the lakes began to form virtually simultaneously with glacial retreat. Terrigenous sediments accumulated in the lakes in Preboreal time. They were replaced by organic sediments about 9140 ± 220 (C14) B. P., i. e. 200–450 years later than in the eastern and southeastern parts of Kalevala marginal deposits. A hiatus was revealed in the deposition of bottom sediments in one of the lakes lying at a higher absolute elevation. The hiatus was due to a drop in the water level in Boreal time caused by a change to a more xeric climate and a glacioisostatic uplift of the crystalline Fennoscandian Shield. Vegetation dynamics from Preboreal time to the present day was reconstructed.

Post-Little Ice Age Development of Coast in the Locality of Kapp Napier, Central Spitsbergen, Svalbard Archipelago

Changes in the position of the shore in the vicinity of Kapp Napier in central Svalbard was described. The overall advance of the shore was probably related to high input of the sediment material originating from erosion of the coastal areas south of the Kapp Napier locality and high input of material from adjacent glacifluvial system of Nordenskiöld glacier with its marginal water streams. Fast evolution of glacier retreat related processes after the Little Ice Age was a secondary driver of the dynamic changes in the central Svalbard coastal areas especially in the first half of the 20th century. The highly dynamic longshore currents in the area altogether with still ongoing glacio-isostatic uplift played an important role in the process as well. The most active parts of the shore experienced advance of almost 100 m since 1908 to 2009. On the other hand, a small part of the coast retreated of about 20 m. Most of the study area experienced aggradation (65%), 30% of the coast was stable and about 5% of the coast has undergone minor retreat. The maximum aggradation rate of 0.96 m/year corresponds well with similar sites in the vicinity.

Quaternary Hydrodynamic Contexts of the Emerging Coasts of Nunavik (Northern Québec, Canada)

Boisson, A. and Allard, M., 2018. Quaternary Hydrodynamic Contexts of the Emerging Coasts of Nunavik (Northern Quebec, Canada). In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 616–620. Coconut Creek (Florida), ISSN 0749-0208.Nunavik (northern Quebec, Canada) is bounded by Hudson Bay to the West and by Hudson Strait and Ungava Bay to the North. These understudied Arctic and Subarctic shores are undergoing glacio-isostatic uplift, with current emergence rates of 5 to 13 mm/yr., counterbalancing the current rise of sea level. A study of the effects of Quaternary hydrodynamic conditions on the emerging coastal geomorphology of Nunavik was conducted based on geotagged videography and photography collected by helicopter between Kuujjuarapik and Kangiqsualujjuaq in August 2015 and August 2016. In total, 45 hours of videography and 37,000 high resolution photographs were taken along the coast. Through detailed segmentation and characterization of that ~ 10,000 km long coastline, one of our main objectives is to better understand the shaping of the emerging coastlines by hydrodynamic processes (waves, tides, sea-ice). The results of this study emphasize on a strong trichotomy between these seaboards because they are very different in terms of tidal conditions, wind and sea-ice climate, morphology and coastal permafrost. In relation to these specific hydrodynamic contexts, conspicuous and poorly documented emerging landforms were identified and described such as boulder barricades along the coast of Ungava Bay, and reworked De Geer moraine ridges along the northeastern coast of Hudson Bay. Coastal risks in Nunavik are also briefly discussed.

СТРАТИГРАФИЯ ДОННЫХ ОСАДКОВ МАЛЫХ ОЗЕР И ПАЛЕОГЕОГРАФИЯ ЗАПАДНОГО БЕРЕГА ОНЕЖСКОГО ЗАЛИВА БЕЛОГО МОРЯ В ПОЗДНЕЛЕДНИКОВЬЕ И ГОЛОЦЕНЕ, "Геоморфология"

Представлены новые данные по литологии, микропалеонтологии и геохронологии донных осадков малых озер, расположенных на западном берегу Онежского залива Белого моря. На основе полученных данных для указанного района реконструирована палеогеографическая обстановка позднеледниковья и голоцена. Установлено, что здесь в позднем дриасе в условиях краевой зоны деградирующего ледника образовывались приледниковые озера. Их осадки в виде палеонтологически немых разнозернистых песков с гравием отмечены в некоторых котловинах побережья до высоты около 140 м над у.м. Спуск этих озер в конце позднего дриаса способствовал формированию единого обширного пресноводного водоема в котловине современного Онежского залива. В начале пребореала при таянии погребенного льда на прилегающей суше происходило заболачивание локальных депрессий и образование низинных болот и торфяников. В конце пребореала - начале бореала при замедлении гляциоизостатического поднятия земной коры, после разрушения ледяной преграды в районе Соловецких островов и притока морской воды в котловину Онежского залива произошло затопление прилегающей к нему территории. Сначала в этом обширном водоеме, а позже в отделившихся от него малых озерах накапливались слоистые алевриты и алевритистые сапропели, перекрывающие торф в разрезах донных отложений. Котловины малых озер отчленялись от основного водоема Онежского залива в разное время на протяжении голоцена по причине гляциоизостатического поднятия и восходящих блоковых движений земной коры.

ГОЛОЦЕНОВАЯ ИСТОРИЯ ДЕЛЬТЫ Р. СЕВЕРНОЙ ДВИНЫ, "Геоморфология"

Дельта р. Северной Двины в голоцене прошла три стадии развития. Эстуарная стадия (~11-7.7 кал. тыс. л. н.) совпадает со временем проникновения морских вод в Двинской залив (губу) Белого моря и завершается выработкой абразионного клифа в отложениях последнего оледенения. Лагунная стадия (~7.7-5.5 кал. тыс. л. н.) характеризуется более высоким, чем современный, длительным стоянием Белого моря, сопровождавшимся слабыми колебаниями его уровня и накоплением характерных органогенных отложений с остатками солоноватоводных микроорганизмов. Стадия дельты выполнения остаточного устьевого залива (~5.5 кал. тыс. л. н. - настоящее время) совпала с падением скоростей гляциоизостатического поднятия и началом активной аккумуляции во всем регионе Белого моря и продолжается до сих пор.

Sediment sequences and palynology of outer South Bay, Manitoulin Island, Ontario: Connections to Lake Huron paleohydrologic phases and upstream Lake Agassiz events

South Bay on the southern coast of Manitoulin Island is a fjord-like embayment connected to Lake Huron by a natural narrow gap in the bay's outer sill 6.5–14 m above the lake. A seismic profile, pollen, plant macrofossil, grain size analyses, and other sediment properties of two piston cores from a shallow outer basin of the bay document a 9 m-thick sediment section comprising rhythmically laminated clay under silty clay containing zones with small molluscan shells and marsh detritus. A sandy pebbly layer under soft silty clay mud overlies these sediments. This stratigraphy represents inundation by deep glacial Lake Algonquin followed by the shallowing Post Algonquin series of lakes, and exposure in the early Holocene by 5 Lake Stanley lowstands in the Lake Huron basin separated by 4 Lake Mattawa highstands. Overflow from South Bay in the first lowstand is thought to have eroded the outer sill gap. Marsh environments are inferred to have formed in the bay during subsequent lowstands. The Lake Mattawa highstands are attributed to outburst floods mainly from glacial Lake Agassiz. Palynological evidence of increased spruce occurrence, an apparent regional climate reversal, during the dry pine period is attributed to cold northwest winds from the Lake Superior basin and a lake effect from the Mattawa highstands in the Lake Huron basin. Lake waters transgressed South Bay following the pine period to form the Nipissing shore on Manitoulin Island. Transfer of Lake Huron basin drainage to southern outlets and continued glacioisostatic uplift of the region led to the present configuration of South Bay and Lake Huron.

Identification and analysis of large paleo-landslides at Mount Burnaby, British Columbia

This paper presents a multi-scale and multidisciplinary study of large, late Pleistocene or early Holocene slumps in Eocene sedimentary rocks at Mount Burnaby, just east of Vancouver, British Columbia (BC). Airborne LiDAR and field data were integrated into a GIS to understand the origin, kinematics, and subsequent history of the landslides. Products derived from the bare-earth LiDAR data include an engineering geomorphology map, shaded relief maps, and several LiDAR slope profiles. To understand the landslides better, we analyzed discontinuities and structural lineaments. The structure of the Eocene rocks underlying Mount Burnaby was compared with trends of local lineaments, and the shape of the coastline of Burrard Inlet and Indian Arm, and trends of regional faults and lineaments identified by previous researchers working in southwest BC. Two main joint systems likely played a key role in conditioning the north slope of Mount Burnaby for failure. The landslides probably happened during or soon after deglaciation of the area at the end of the Pleistocene on the steep north face of Mount Burnaby after a 200-m fall in relative sea level caused by glacio-isostatic uplift of the crust.

Comparison of airborne LiDAR and shipboard acoustic data in complex shallow water environments: Filling in the white ribbon zone

Shallow coastal areas of oceans, seas and lakes pose significant remote sensing and navigational challenges due to the transient nature of bathymetric features that characterize these areas (e.g., shoals and shoaling). Seabed data/maps often represent these areas as “white ribbon” zones, where sparse data coverage presents a particular challenge to defining and enforcing sustainable use of marine resources. Given the lengthy perimeter of coastlines, there is a need for cost-efficient methods for producing high resolution maps of shallow areas. The research described here compares airborne light detection and ranging (LiDAR) with shipboard acoustic surveys around the Kvarken Archipelago of the northern Baltic Sea.The Kvarken Archipelago includes a unique, brackish shallow water marine environment with a number of moraines. The landscape of the area is characterised by fields of ridged, washboard-like De Geer moraines. The moraines combined with an ongoing glacio-isostatic uplift typical of the area, lead into succession of the elevated structures from the seafloor to land, where present seabed structures will rise on land in future. The ongoing modification of the environment by both climatic and geologic forces contributes to complex geomorphic and ecological feedback systems operating on a range of spatial and temporal scales.Airborne LiDAR can provide high resolution remote sensing data on shallow coastal areas. The technology is especially effective in areas with very shoal waters, like those found along the Finnish coast. LiDAR enables continuous detection of topographic (elevation) and bathymetric (depth) data and can thus generate continuous maps of transition zones between continental and marine areas. Environmental conditions such as water clarity and ice cover can affect LiDAR depth detection capabilities; these conditions require complementary accuracy assessment strategies. As LiDAR cannot determine detailed information on seafloor surface substrate, and anything on subsurface substrate type, geological conditions are determined through the application of acoustic-seismic methods, sediment sampling and underwater video.Data from LiDAR surveys provide a detailed topographic and bathymetric map of the study area up to water depths of 14m. The seabed bathymetry model shows a series of elevated, narrow, elongate features that appear throughout the study area. These parallel ridges represent the uppermost geomorphic features of the seafloor. Interpretation of acoustic bathymetric surveys indicates that these ridges are De Geer moraines. The general orientation of these moraines differs from that associated with older features of the northern Kvarken Archipelago. Eroded remnants of older De Geer moraines are overprinted at a high angle by the younger landforms. De Geer moraines in the study area thus represent two phases of deglaciation and finally the eastward ice-sheet/ice edge retreat. The combined approach of using LiDAR and acoustic bathymetric data provides new insights into past glacial dynamics of the Kvarken Archipelago and the Gulf of Bothnia.

Impact of the ‘Little Ice Age’ climate cooling on the maar lake ecosystem affected by penguins: A lacustrine sediment record, Penguin Island, West Antarctica

A Pliocene-age volcano on Penguin Island became active again in the Pleistocene/Holocene, forming the main cone of the island – Deacon Peak, and leaving late-Holocene phreatomagmatic craters, including ‘Petrel Crater’, about 200 m in diameter and filled currently by a maar lake with a flat bottom at 18 m water depth. Petrographic, geochemical, photosynthetic pigment, and diatom data from the 72-cm-long sediment core reveal that the crater was initially a marine lagoon with typical phytoplankton assemblages. Most probably, tectonic–volcanic activity about 1250 years ago, documented in tephra fallout, triggered an abrupt glacio-isostatic uplift that separated the lake from the sea. The horizon of tephra, probably from the Deception Island volcano, marks a sudden change in environment from brackish to lacustrine. The ecological evolution of the lake was initially constrained by an uplift, whereas the influence of marine water vanished with time, the lake became meromictic, and the freshwater mixolimnion layer expanded, while the monimolimnion became anoxic due to the influence of a penguin rookery situated on the shore. During the ‘Little Ice Age’ (LIA), the maar may have been covered by permanent ice. A discharge of mineralized guano from the possibly enlarged penguin rookery on the lake shore caused an expansion of the anoxic monimolimnion to the ice surface and an important reduction of autochthonous lacustrine biota of the maar, whereas a substantially increased participation of allochthonous biota passively supplied with guano. That record in the lake sediment core reaffirms the occurrence of a regional LIA event in the maritime Antarctic.

Holocene stratigraphy of the Ångermanälven River estuary, Bothnian Sea

This study explores the Holocene depositional succession at the IODP Expedition 347 sites M0061 and M0062 in the vicinity of the Angermanalven River estuary in the Bothnian Sea sector of the Baltic Sea in northern Scandinavia. Site M0061 is located in a coastal offshore setting (87.9 m water depth), whereas site M0062 is fully estuarine (69.3 m water depth). The dataset comprises acoustic profiles and sediment cores collected in 2007 and late 2013 respectively. Three acoustic units (AUs) were recognized. Lowermost AU1 is interpreted as a poorly to discontinuous stratified glaciofluvial deposit, AU2 as a stratified conformable drape of glaciolacustrine origin, and AU3 as a poorly stratified to stratified mud drift. A strong truncating reflector separates AU2 and AU3. Three lithological units (LUs) were defined in the sediment cores. LU1 consists of glaciofluvial sand and silt gradating into LU2, which consists of glaciolacustrine varves. A sharp contact interpreted as a major unconformity separates LU2 from the overlying LU3 (brackish-water mud). In the basal part of LU3, one debrite (site M0061) or two debrites (site M0062) were recognized. Information yielded from sediment physical properties (magnetic susceptibility, natural gamma ray, dry bulk density), geochemistry (total carbon, total organic carbon, total inorganic carbon and nitrogen), and grain size support the LU division. The depositional succession was formally subdivided into two alloformations: the Utansjo Alloformation and overlying Hemson Alloformation; the Utansjo Alloformation was further subdivided into two lithostratigraphic formations: the Storfjarden and Abordson formations. The Storfjarden (sandy outwash) and Abordson (glaciolacustrine rhythmite) formations represent a glacial retreat systems tract, which started at ca. 10.6 kyr BP. Their deposition was mainly controlled by meltwater from the retreating ice margin, glacio-isostatic land uplift and the regressive (glacial) lake level. The Hemson Alloformation (organic-rich brackish-water mud) represents a period of forced regression, starting possibly at ca. 9.5 kyr BP. At about 7 kyr BP, brackish water reached the study area as a result of the mid-Holocene marine flooding of the Baltic Sea Basin, but the rapid land uplift soon surpassed the associated (Littorina) transgression. Changed near-bottom current patterns, caused by the establishment of a permanent halocline, and the reduced sediment consistency caused by increased organic deposition resulted in a sharp and erosional base of the brackish-water mud. Estuarine processes and salinity stratification at site M0062 started to play a more important role. This study applies a combined allostratigraphic and lithostratigraphic approach over the conventional Baltic Sea stages. This approach makes it more straightforward to study this Baltic Sea deglaciation–postglacial sequence and compare it to other formerly glaciated shallow sea estuaries.

The newest stage of development of the White Sea depression

Analysis of materials on the geological structure and tectonics of the White Sea depression area suggests that this depression existed in the Middle Pleistocene and was connected with the World Ocean. It is still impossible to determine the exact time of its formation due to an insufficient knowledge of the depression loose cover. However it is most likely that the depression was formed in the Late Miocene and Early Pliocene, when after the regressive development of the continental margin the shelf subsidence began. Probably in the Holocene the divergent regime was replaced by the transform regime. This period saw the subsidence of the Kandalaksha graben to about 150 m and the formation of the Kolvitsa graben. The crystalline rocks surrounding Kandalaksha bay were involved in the subsidence which is reflected in the isobase curve of the glacioisostatic uplift of the area. The combined impact of the tectonic component and the glacioisostatic uplift led to a rise of tensions which discharge caused a high seismic activity of the Kandalaksha graben and its environs.

An allostratigraphic approach to subdivide fine-grained sediments for urban planning

Fine-grained sediments in southern Finland were deposited during the retreat of the continental Fennoscandian ice-sheet at around 13,000 cal BP, leaving subsequent ice-contact deposits and postglacial lake and, finally, the modern brackish water Baltic Sea basin (BSB). As a result of the strong glacioisostatic land uplift of the region, these sediments today lie above sea-level in coastal Finland. The recent expansion of cities to locations where superficial sediments are more challenging for construction purposes has increased the need for comprehensive understanding of the properties and geometry of these fine-grained superficial deposits. Commonly used site-specific lithostratigraphical characteristics of clayey deposits run the risk of ambiguous correlation between sites because of different types of postglacial depositional settings. The present study applies an allostratigraphical approach to classify late- and postglacial clayey deposits using examples from four sedimentary basins in the vicinity of the city of Espoo along the southern coast of Finland. This entails a reinterpretation of 17 core logs collected during the period 2006–2009 and reported in earlier studies, combined with examination of five new cores collected in 2016 coupled with borehole measurements of resistivity-temperature and electrical resistivity tomography (ERT). Physical proxies and sediment characteristics demonstrate that grey postglacial lacustrine silty (Ancylus Lake) clay is truncated at the top by an undulating erosional surface (unconformity), which is covered by a silt to sand layer a few centimetres thick that has a gradual-bioturbated upper contact to the greenish-grey brackish water (Litorina Sea) mud. Sediments above and below the unconformity are intensely bioturbated, and black mottling of Fe-monosulphide is observed in the brackish water mud. Evidently, this unconformity is of high engineering-geological significance because the organic-rich brackish water mud has a poorer bearing capacity and higher abundance of sulphide minerals that form sulphuric acid upon oxidation. It is demonstrated that this unconformity is spatially well recognised and provides a key stratigraphic marker for wider and more accurate comparison between sites with fine-grained deposits in the Helsinki metropolitan area and potentially in other urban areas in the northern Baltic Sea region.

Postglacial mass movements and depositional environments in a high-latitude fjord system – Hardangerfjorden, Western Norway

High resolution acoustic data and a 15.7m long sediment core from the Hardangerfjorden system, western Norway, have been analyzed to increase our knowledge on depositional environments, submarine mass movement trigger mechanisms and submarine mass movement frequencies in high latitude fjord systems. The seismic profiles analyzed show that an up to 160m thick glacimarine-dominated unit, of probably Younger Dryas age, has been deposited above the acoustic basement. A <55m thick unit, comprising stacked mass transport deposits (MTDs) has been deposited atop the glacimarine unit. The identified mass movement events comprise 19 MTDs (MTD1–19), which have transported sediment volumes of up to 0.4km3 and initiated turbidity currents resulting in the deposition of up to 13m thick turbidite layers. The established chronostratigraphical framework reveals high mass movement activity in Hardangerfjorden at 11100–8200cal.yrsBP (Early Holocene) and at 4100cal.yrsBP to present (Late Holocene). 14 MTDs have been dated to the Early Holocene, which is a time period characterized by high sedimentation rates (1.1mm/yr), giving a mass movement recurrence rate of 1/200years. Several of these failure events are suggested to have been triggered by regional mechanisms such as earthquakes linked to glacioisostatic uplift. Some of the MTDs of that time could potentially be caused by rock avalanches. Furthermore, it seems that the identified 8200cal.yrsBP MTD5 coincides with the age of the Storegga tsunami, suggesting that processes related to this event may have caused sediment failure in the inner Hardangerfjorden. During the mid-Holocene (8200–4100cal.yrsBP), a time period which was characterized by low sedimentation rates of 0.1–0.2mm/yr and a warmer and wetter climate, mass movement events were absent in the study area. The renewed slide activity in the Late Holocene, comprising four MTDs, is probably related to climatic processes, earthquakes and rock avalanches, resulting in a mass movement recurrence rate of 1/1000years for this time period. This study, thus, underlines the importance of high-latitude fjords, also in a global context, as systems where local, regional and external geological forces interact to impose highly dynamic postglacial depositional environments.

Seismites resulting from high-frequency, high-magnitude earthquakes in Latvia caused by Late Glacial glacio-isostatic uplift

Geologically extremely rapid changes in altitude by glacial rebound of the Earth crust after retreat of the Scandinavian Ice Sheet at the end of the last Weichselian glaciation influenced the palaeogeography of northern Europe. The uplift of the Earth crust apparently was not gradual, but shock-wise, as the uplift was accompanied by frequent, high-magnitude earthquakes. This can be deduced from strongly deformed layers which are interpreted as seismites. Such seismites have been described from several countries around the Baltic Sea, including Sweden, Germany and Poland.Now similarly deformed layers that must also be interpreted as seismites, have been discovered also in Latvia, a Baltic country that was covered by an ice sheet during the last glaciation. The seismites were found at two sites: Near Valmiera in the NE part and near Rakuti in the SE part of the country. The seismites were found in sections of about 7 m and 4.5 m high, respectively, that consist mainly of glaciofluvial and glaciolacustrine sands and silts. At the Valmiera site, 7 seismites were found, and at the Rakuti site these were even 12 seismites.The two sections have not been dated precisely up till now, but lithological correlations and geomorphological characteristics suggest that the sediments at the Valmiera site cannot be older than 14.5 ka. Because the accumulation of the section did not take more than about 1000 years, the average recurrence time of the high-magnitude (M ≥ 4.5–5.0) earthquakes must have been maximally only 100–150 years, possibly only 6–7 years. The sediments at Rakuti must also have formed within approx. 1000 years (17–16 ka), implying a recurrence time of high-magnitude earthquakes of maximally once per 100–200 years.

Postglacial environmental succession of Nettilling Lake (Baffin Island, Canadian Arctic) inferred from biogeochemical and microfossil proxies

Abstract Nettilling Lake (Baffin Island, Nunavut) is currently the largest lake in the Canadian Arctic Archipelago. Despite its enormous size, this freshwater system remains little studied until the present-day. Existing records from southern Baffin Island indicate that in the early postglacial period, the region was submerged by the postglacial Tyrell Sea due to isostatic depression previously exerted by the Laurentide Ice Sheet. However, these records are temporally and spatially discontinuous, relying on qualitative extrapolation. This paper presents the first quantitative reconstruction of the postglacial environmental succession of the Nettilling Lake basin based on a 8300 yr-long high resolution sedimentary record. Our multi-proxy investigation of the glacio-isostatic uplift and subsequent changes in paleosalinity and sediment sources is based on analyses of sediment fabric, elemental geochemistry (μ-XRF), diatom assemblage composition, as well as on the first diatom-based oxygen isotope record from the eastern Canadian Arctic. Results indicate that the Nettilling Lake basin experienced a relatively rapid and uniform marine invasion in the early Holocene, followed by progressive freshening until about 6000 yr BP when limnological conditions similar to those of today were established. Our findings present evidence for deglacial processes in the Foxe Basin that were initiated at least 400yrs earlier than previously thought.

Holocene Relative Sea-Level Changes from Near-, Intermediate-, and Far-Field Locations

Holocene relative sea-level (RSL) records exhibit spatial and temporal variability that arises mainly from the interaction of eustatic (land ice volume and thermal expansion) and isostatic (glacio- and hydro-) factors. We fit RSL histories from near-, intermediate-, and far-field locations with noisy-input Gaussian process models to assess rates of RSL change. Records from near-field regions (e.g., Antarctica, Greenland, Canada, Sweden, and Scotland) reveal a complex pattern of RSL fall from a maximum marine limit due to the net effect of eustatic sea-level rise and glacio-isostatic uplift with rates of RSL fall as great as −69 ± 9 m/ka. Intermediate-field regions (e.g., mid-Atlantic and Pacific coasts of the USA, Netherlands, Southern France, St. Croix) display variable rates of RSL rise from the cumulative effect of eustatic and isostatic factors. Fast rates of RSL rise (up to 10 ± 1 m/ka) are found in the early Holocene in regions near the center of forebulge collapse. Far-field RSL records exhibit a mid-Holocene highstand, the timing (between 8 and 4 ka) and magnitude (between <1 and 6 m) of which varies among South America, Africa, Asia, and Oceania regions.

SEISMOTECTONIC EFFECTS OF THE QUATERNARY ICE SHEET DEVELOPMENT IN THE KOLA REGION

Typical paleoseismic dislocations have been detected by field observations in the Kola Peninsula. The map of ancient earthquake epicenters was compiled on the basis of geological data and aerial photograph interpretation. The epicenters mainly concentrate in the west and in the center of the Kola Peninsula in the area, which has been occupied by active ice during the Older and Younger Dryas or near the distal side of the Older Dryas marginal ridges. The increase of seismotectonic activity took place after deglaciation of the territory owing mainly to crustal deformation caused by glacioisostatic uplift, which is going on until now.