Boreas最新文献

{"title":"Flow-pattern evolution of the Scandinavian Ice Sheet indicated by the subglacial lineation record over Norway, Sweden and Finland","authors":"Frances E. G. Butcher,&nbsp;Anna L. C. Hughes,&nbsp;Helen E. Dulfer,&nbsp;Christopher D. Clark,&nbsp;Jeremy C. Ely,&nbsp;Emma L. M. Lewington,&nbsp;Benjamin M. Boyes,&nbsp;Alex C. Scoffield,&nbsp;Stephen Howcutt,&nbsp;Christiaan R. Diemont","doi":"10.1111/bor.70050","DOIUrl":"https://doi.org/10.1111/bor.70050","url":null,"abstract":"<p>Streamlined subglacial bedforms, including drumlins, mega-scale glacial lineations, crag-and-tails and roche moutonnées, provide evidence for the past flow of large mid-latitude ice sheets during the late Quaternary. Empirical reconstructions of palaeo-ice sheet flow, based on such landforms, provide valuable insights into how ice sheets evolve over time and adjust their internal dynamics in response to climate change. We present a new 25-stage reconstruction of changing flow directions of the Scandinavian Ice Sheet (SIS) based on systematic mapping of ~240 000 subglacial bedforms across Norway, Sweden, Finland and parts of NW Russia. Of these, 23 stages depict the ice flow evolution during advance and retreat of the SIS through Marine Isotope Stage (MIS) 2. Two additional stages likely represent flow patterns of an earlier ice sheet (potentially MIS 4 or older). Our reconstruction was enabled by the recent revolution in the availability of high-resolution (1–2 m) digital terrain models. It is based on 611 flowsets, which summarise discrete ice-flow patterns recorded by subglacial lineations and are individually categorised by their glaciodynamic contexts. The reconstruction honours the relative-age chronology of flowsets indicated by cross-cutting relationships of the subglacial lineations. We reconstruct, and provide maps of, changing ice-sheet flow patterns and the migration of ice divides starting with ice-sheet inception, through advance and subsequent deglaciation, and ultimately the fragmentation into independent ice masses. The primary ice divide migrated up to 500 km and developed a branched configuration during deglaciation. The reconstruction of SIS flow patterns we present is the most detailed and comprehensive to date, and the fact that we independently verify many properties of the ice sheet invoked by earlier workers is testament to the quality, rigour and enduring legacies of those studies. We release flowsets, relative chronology and flow-pattern data along with a dataset of ~58 000 lineation linkages which summarise our detailed landform mapping and were invaluable for reconstructing ice-flow patterns at the ice-sheet-scale. In releasing these data, we intend for them to serve as useful inputs or comparative data for future studies in palaeoglaciology. This includes, for example, approaches combining flow pattern information with numerical ice sheet modelling to improve representations of ice sheet behaviour. Such improvements should yield increased robustness of information on time-varying glacio-isostatic loading by the ice sheet, relevant for sea-level forecasting. Our datasets also have wide utility for applications beyond palaeoglaciology, such as for mineral exploration.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"55 3","pages":"612-669"},"PeriodicalIF":2.3,"publicationDate":"2026-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.70050","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148534004","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Revised classification of glaciofluvial landforms in the Finnish sector of the Fennoscandian Ice Sheet","authors":"Jussi Hovikoski,&nbsp;Jukka-Pekka Palmu,&nbsp;Tapio Väänänen,&nbsp;Markus Valkama,&nbsp;Antti E. K. Ojala,&nbsp;Satu Putkinen,&nbsp;Reijo Pitkäranta","doi":"10.1111/bor.70060","DOIUrl":"https://doi.org/10.1111/bor.70060","url":null,"abstract":"<p>Effective and sustainable land use, conservation, and the use of geological resources (incl. raw materials, aggregates and groundwater) require a clear classification system of sedimentary units, with well-defined vocabulary and unified mapping practices. To ensure harmonization of the GTK's (Geological Survey of Finland) map database of Finnish Quaternary surficial features, classification criteria for glaciofluvial landforms have been updated. The work is based on earlier geological field mapping of surficial Quaternary deposits as well as previous and ongoing LiDAR DEM-based mapping of glaciofluvial landforms in Finland. In this paper, we present the updated classification and terminology, discuss the defining criteria of glaciofluvial map unit types and show their representative examples. Inherent challenges and limitations of this remote sensing-based mapping approach are also discussed.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"55 3","pages":"702-716"},"PeriodicalIF":2.3,"publicationDate":"2026-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.70060","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148522784","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Drilling the Marathousa palaeo-lake in Greece (Peloponnese): inferring the environmental context of a Middle Pleistocene archaeological site","authors":"Ines J. E. Bludau,&nbsp;Bernd Wagner,&nbsp;Uwe Kirscher,&nbsp;Maria Schindler,&nbsp;Charlotte Zachow,&nbsp;Johannes Schmidt,&nbsp;Niklas Leicher,&nbsp;Giovanni Muttoni,&nbsp;Serena Perini,&nbsp;Vangelis Tourloukis,&nbsp;Eleni Panagopoulou,&nbsp;Panagiotis Karkanas,&nbsp;Katerina Harvati,&nbsp;Annett Junginger","doi":"10.1111/bor.70061","DOIUrl":"https://doi.org/10.1111/bor.70061","url":null,"abstract":"<p>The Megalopolis Basin is located in the central Peloponnese (Greece), a region that is situated along one of the primary Pleistocene biogeographical corridors for intracontinental hominin migration. The basin comprises several hundred metres of Plio-Pleistocene sediments alternating between clastics and lignites. Of these sediments, a 6 m thick succession deposited during the cold Marine Isotope Stage (MIS) 12 (~480–420 ka) was intensely studied after the discovery of evidence for hominin presence in these strata at the Marathousa 1 Lower Palaeolithic site. The local environmental conditions prior to and after this period, however, are still unknown. Here, we present the results of sedimentological analyses of two &gt;100 m long drill cores (MAR18-1A and MAR18-2A) and two outcrops (MAR19-2AP, Choremi-6) in order to provide palaeoenvironmental constraints on the Megalopolis Basin between ~780 and 340 ka. Our age control is based on palaeomagnetic analysis conducted on the drill core MAR18-1A and the Choremi-6 outcrop, as well as correlations to formerly studied cores and outcrops. The geochemical and lithological proxies and their statistical processing reveal that the basin was characterized by a periodically changing environment influenced by a deltaic river during dry and/or cold intervals (clastic layer deposition) and lacustrine environments that were fringed by lush, limno-telmatic vegetation during humid and/or warm periods (lignite seam formation). Our results provide high-resolution insights into climatic changes in the immediate surrounding of the archaeological sites in the Megalopolis Basin during the Early to Middle Pleistocene, disclosing further investigation opportunities on palaeoclimate, palaeoenvironment and human activity in the region.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"55 3","pages":"866-884"},"PeriodicalIF":2.3,"publicationDate":"2026-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.70061","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148532844","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Late Holocene moisture variability in Arctic Alaska from chitin δ18O","authors":"Briana A. Edgerton,&nbsp;Melissa L. Chipman","doi":"10.1111/bor.70052","DOIUrl":"https://doi.org/10.1111/bor.70052","url":null,"abstract":"<p>Amplified warming in the Arctic has resulted in reduced sea-ice extent, which can impact regional climate dynamics. Elucidating past moisture variability in response to changing temperatures and sea-ice conditions can offer insight into how anthropogenic climate change may impact Arctic areas such as the Alaskan North Slope in the future. We contribute a new high-resolution record of precipitation variability from Lake GTH90 located on the Alaskan North Slope. This new record is based on the isotopic composition of chitin from lake sediments and adds to a growing suite of Late Holocene climate records in northern Alaska. An overall decrease in δ¹⁸O values from 3.5 cal. ka BP to present at Lake GTH90 is coincident with Neoglacial cooling associated with a millennial-scale decrease in summer insolation. The highest and most variable δ¹⁸O values occur between 3.5 and 2.6 cal. ka BP and the lowest values are centred around 0.5 cal. ka BP, indicating isotopically depleted precipitation during the Little Ice Age. Isotopic variability in our record on centennial timescales is consistent with temporal variability in sea-ice extent in the Arctic Ocean in the Late Holocene, suggesting that periods of high sea-ice extent inhibited Arctic moisture sources and long-distance moisture transport from the North Pacific became dominant. In addition, we compare regional records to evaluate how shifts in the strength and position of the Aleutian Low may have also contributed to Late Holocene precipitation in this region.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"55 3","pages":"751-767"},"PeriodicalIF":2.3,"publicationDate":"2026-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.70052","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148533131","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An overview of Mass Accumulation Rates in key Polish loess–palaeosol sequences derived from luminescence chronologies","authors":"Maksymilian Jędrzejowski,&nbsp;Zoran M. Perić,&nbsp;Zdzisław Jary,&nbsp;Slobodan Marković,&nbsp;Piotr Moska,&nbsp;Grzegorz Poręba,&nbsp;Agnieszka Szymak,&nbsp;Andrzej Wojtalak","doi":"10.1111/bor.70067","DOIUrl":"https://doi.org/10.1111/bor.70067","url":null,"abstract":"<p>Loess–palaeosol sequences (LPS) represent one of the most important continental archives of late Quaternary environmental change in Europe. Establishing reliable chronologies is essential for reconstructing dust dynamics and for correlating regional loess stratigraphies. In this study, we present the first systematically derived mass accumulation rate (MAR) dataset for six key Polish LPS, based on high-resolution Optically Stimulated Luminescence dating of the 45–63 μm quartz fraction. Bayesian age–depth models were constructed using the Bacon software. The results demonstrate pronounced temporal and spatial variability in loess accumulation across southern Poland. All profiles show maximum MARs during MIS 2, with exceptionally high values exceeding 1000 g m⁻² a⁻¹ at Trzebnica, Tyszowce and Strzyżów sites. In contrast, Zaprężyn site exhibits lower MARs with only localized peaks. The results highlight the utility of luminescence-derived MARs for investigating regional aeolian dynamics, while also emphasizing the methodological limitations imposed by chronological uncertainties and sampling resolution.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"55 3","pages":"835-845"},"PeriodicalIF":2.3,"publicationDate":"2026-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.70067","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148534228","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Luminescence dating of coastal deposits from the Chanthaburi Plain, Thailand","authors":"Margarita Nuss,&nbsp;Sakonvan Chawchai,&nbsp;Savanna Kager,&nbsp;Smith Leknettip,&nbsp;Yunyi Li,&nbsp;Kannika Wangritthikraikul,&nbsp;Frank Preusser","doi":"10.1111/bor.70063","DOIUrl":"https://doi.org/10.1111/bor.70063","url":null,"abstract":"<p>The ongoing global sea-level rise urges us to better understand the dynamics of coastal processes for predicting future changes. Sedimentary deposits reflect past coastal environments but require precise chronological data to place evidence into a temporal context. While radiocarbon dating is widely employed, it is associated with several methodological challenges and frequently there is an absence of datable material in coastal deposits. Luminescence dating provides an important advantage over radiocarbon by directly determining the time of sediment deposition. However, this method is affected by problematic issues such as partial bleaching, bioturbation and dose rate assessment, which can lead to inaccurate age determinations. As a case study demonstrating good scientific practice in luminescence dating, we investigated deposits from the Chanthaburi Plain, Thailand, for reconstructing past coastal dynamics. Luminescence screening is used to identify potential signal disturbances and select appropriate sample positions in the drill cores. Luminescence dating was performed on 13 samples accompanied by detailed analysis regarding dose rate with a focus on water content and radioactive disequilibrium. The dated samples indicate depositional ages ranging between 7.2 and 4.6 ka. Comparison with radiocarbon ages (18 samples) reveals that plant material often represents modern roots and that molluscs tend to systematically underestimate the sedimentation age, likely due to partial recrystallisation. Our data suggest at <i>c</i>. 6.5 ka, a location of the coastline ~8.1 km inland from the present position. At around 4.6 ka, the coastline was about 7.2 km from the present shore. Together with previously published data, this indicates a sea-level regression from the Middle Holocene highstand towards the Late Holocene.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"55 3","pages":"846-865"},"PeriodicalIF":2.3,"publicationDate":"2026-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.70063","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148532837","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Weichselian history of the Fennoscandian Ice Sheet centre, Kvarken archipelago, western Finland—flow shifts, thermal regime and deglaciation","authors":"Niko Putkinen,&nbsp;Tapani Tervo,&nbsp;Adrian M. Hall,&nbsp;Juha P. Lunkka,&nbsp;Pertti Sarala,&nbsp;Olli Breilin,&nbsp;Jari Nenonen","doi":"10.1111/bor.70064","DOIUrl":"https://doi.org/10.1111/bor.70064","url":null,"abstract":"<p>Rapid thaw of the Earth's cryosphere in response to anthropogenic warming highlights the need to identify and understand the contrasting signatures of past ice-sheet stability and collapse. The Kvarken archipelago, western Finland, at the centre of the former Fennoscandian Ice Sheet (FIS), has been designated a UNESCO World Heritage site in recognition of the exceptional preservation of glacial landforms exposed by rapid (10 mm a⁻¹) postglacial isostatic uplift. Detailed mapping of hard and soft glacial bedforms allows reconstruction of ice sheet dynamics over the last glacial cycle. Striation orientation measurements (<i>n</i> ~ 1100) were made at 700 sites on Precambrian gneiss and granite bedrock surfaces around the present shorelines. The striation data are classified into relative age categories and broader striation arrays to identify ice-flow paths and then integrated with other directional indicators from overlying glacial sediments and landforms. The full data set reveals a sequence of six ice-flow stages, which are then placed in a revised event and chronostratigraphic model for the wider Ostrobothnia region. After a major glacial erosion phase in Kvarken in late MIS 6, ice sheets returned in MIS 4 and MIS 3. During brief sliding phases, till sheets were deformed and eroded, but cross-striations indicate that bedrock erosion was locally weak (&lt;0.5 m) until after the last glacial maximum. At 11.6 ka, summer temperatures in Fennoscandia rose abruptly by 3–6 °C, and large volumes of meltwater reached the glacier bed. At 10.7–10.5 ka, a fast ice-flow phase, the Gävle Oscillation, developed in the Bothnian basin. A &lt;400-year pulse of intense subglacial activity began in Kvarken, with abrupt and often pronounced switching of flow, production of new striation arrays, widespread erosion of till and bedrock and the formation of new soft bedforms. Existing till sheets were extensively glaciotectonically deformed into a young set of ribbed moraines. Local ice-flow events led to the development of low-relief megaflutings, drumlins and flutings. Bedrock was hydraulically damaged by large discharges of pressurized meltwater flowing in subglacial meltwater corridors, generating dense concentrations of large boulders. The ice margin retreated at 200–700, even 1000 m a⁻¹, with deposition of De Geer moraines in water depths of 220 m, before final deglaciation at 10.4–10.3 ka. Our Kvarken case study indicates that after slow erosion beneath stable ice sheet centres in MIS 4 and MIS 3/2, abrupt Early Holocene warming triggered ice sheet collapse and brought profound changes at the ice sheet bed over centennial time scales.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"55 3","pages":"670-701"},"PeriodicalIF":2.3,"publicationDate":"2026-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.70064","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148532861","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thorncliffe Formation: A proglacial to subglacial lacustrine basin sequence, Greater Toronto Region, Canada","authors":"David R. Sharpe,&nbsp;Charles E. Logan,&nbsp;Ross D. Knight,&nbsp;Andre J.-M. Pugin","doi":"10.1111/bor.70058","DOIUrl":"https://doi.org/10.1111/bor.70058","url":null,"abstract":"<p>Thorncliffe Formation (southern Ontario, Canada) sedimentary architecture, extent, facies trends, contacts and composition, combined with hydraulic data, define fundamental glacial basin depositional environments. Thorncliffe Formation (TF) comprises an ~50–100 m thick glaciofluvial–glaciolacustrine sediment sequence covering ~8000 km² east of Niagara Escarpment, from Lake Ontario north to the Canadian Shield. These sediments include aquifers that supply water to &gt;200 000 people, with significant untapped resources in the Greater Toronto Area. A comprehensive regional dataset enables reassessment of TF character, origin and age within a 3Dmodel of the basin sediments. The TF is primarily basin mud (~90%) with associated source channels (&lt;100 m deep) containing fining-upward sequences (~10%) of gravel, sand, rhythmites and diamicton. TF deposition began as proglacial lake organic-rich sediments accumulated in front of an advancing ice margin that obstructed Great Lakes drainage. Rising lake levels subsequently ponded meltwater against the ~100 m high Niagara Escarpment. When advancing ice overtopped the escarpment, TF basin evolved into a captured subglacial lake. Organic-poor, stratified TF subglacial lake sediments were generally deposited conformably with overlying regional Newmarket Till (NT). Integration of high-resolution subsurface data sets including seismic profiles, continuous cores, lake bluff sections and well monitoring data, enables the development of a robust conceptual framework for TF sediment architecture and depositional setting. This synthesis supports interpreting TF as high-energy, subaqueous channel-fan systems discharged from mapped inflow corridors into a muddy subglacial lake basin. The contact between glacial (NT) and inferred subglacial lake sediments (TF) exhibits interbedding, gradation, mounding and boulder scour features indicative of synchronous sedimentation beneath an ice-covered subglacial lake. Episodic ice lifting from and lowering back to the bed likely occurred during meltwater discharge events. TF data support established theory that subglacial lakes were common beneath continental ice sheets. TF sediment characteristics can help to identify subglacial lake settings in other glaciated terrain.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"55 3","pages":"717-750"},"PeriodicalIF":2.3,"publicationDate":"2026-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.70058","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148534117","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A North Greenland-wide in situ cosmogenic 14C ice sheet chronology since the Lateglacial","authors":"Anne Sofie Søndergaard,&nbsp;Astrid Rosenberg,&nbsp;Mads Faurschou Knudsen,&nbsp;Kristina Hippe,&nbsp;Marcus  Christl,&nbsp;Negar Haghipour,&nbsp;Olivia Steinemann,&nbsp;Kurt H. Kjær,&nbsp;Nicolaj Krog Larsen","doi":"10.1111/bor.70029","DOIUrl":"https://doi.org/10.1111/bor.70029","url":null,"abstract":"<p>Knowledge of the glacial history of the North Greenland Ice Sheet is crucial due to its high sensitivity to climate change. However, because the ice sheet in this region is predominantly cold-based, resulting in low erosion rates, using ¹⁰Be exposure dating to establish reliable ice sheet chronologies has proven very challenging due to nuclide inheritance. In this study, we measure 16 rock samples for their <i>in situ</i> ¹⁴C concentration, most of which already showed ¹⁰Be nuclide inheritance, resulting in apparent exposure ages pre-dating the most recent deglaciation. We combine our new results with seven already published <i>in situ</i> ¹⁴C exposure ages to build a North Greenland-wide <i>in situ</i> ¹⁴C ice sheet chronology based on a total of 20 boulder and three bedrock samples. Resulting <i>in situ</i> ¹⁴C ages range from 4.8 to 22.4 ka, and more than half of our <i>in situ</i> ¹⁴C exposure ages show signs of excess nuclides, pre-dating the most recent deglaciation at individual sample sites. We believe the excess nuclides could be a result of limited erosion during the Last Glacial Maximum (LGM) and a combination of pre-LGM exposure, supraglacial pre-deposition exposure and possibly thin ice cover. Our new large-scale <i>in situ</i> ¹⁴C data set contributes important knowledge on the glacial history of North Greenland and ice-bed properties in this region. Despite challenges, all <i>in situ</i> ¹⁴C exposure ages except two are younger than their ¹⁰Be counterpart, which highlights the potential and necessity of <i>in situ</i> ¹⁴C exposure dating in regions with cold-based ice and low erosion rates.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"55 2","pages":"327-339"},"PeriodicalIF":2.9,"publicationDate":"2026-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.70029","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147686284","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Morphology and distribution of lakes under the Laurentide Ice Sheet: implications for ice flow dynamics","authors":"Sarah M. Principato,&nbsp;Carissa M. Mobley","doi":"10.1111/bor.70034","DOIUrl":"https://doi.org/10.1111/bor.70034","url":null,"abstract":"<p>This study examines the distribution and morphology of lakes under the Laurentide Ice Sheet (LIS) to investigate relationships with ice flow velocity, bedrock and basal thermal regime. Palaeo-ice streams and lobes were important components of the LIS, and properties of lakes in those regions are quantified at high resolution. Lake polygon shapefiles obtained from the HydroLAKES database contain data including water depth, volume and elevation. ArcGIS Pro is used to measure lake area, length, width, elongation, orientation, parallel conformity, density and packing. Approximately 982 282 natural lakes were identified in the region of North America covered by the maximum extent of the LIS during the Last Glacial Maximum. Density of lakes is highest in terrestrial regions surrounding Hudson Bay, and lake density decreases closer to the ice-sheet margin. Packing shows similar patterns to density with the exceptions of regions covered by remnants of proglacial lakes and non-glacial lakes. Close examination of density and packing under palaeo-ice streams and lobes shows statistically significant differences, with greater lake density and packing under palaeo-ice streams than lobes. Bedrock substrate also plays a key role in lake density and packing, with higher lake density under palaeo-ice streams flowing over the Canadian Shield compared with density and packing of lakes under palaeo-ice streams flowing on sedimentary bedrock. Lakes under palaeo-ice streams have higher parallel conformity than lobes, with orientation in both following ice flow paths. Elongation ratios of lakes under palaeo-ice streams and lobes are similar. Regions with high lake density are associated with intense ice scouring on the Canadian Shield, while regions with low lake density on sedimentary bedrock suggest a transition from initially high erosion of soft-bedded terrain followed by depositional processes dominating. High parallel conformity of lakes under palaeo-ice streams provides evidence for fast ice flow, similar to the presence of mega-scale glacial lineations. Quantifying lake morphology and distribution under the LIS provides a useful proxy for ice-sheet dynamics and may help better understand conditions under modern ice sheets, especially in regions of fast ice flow.</p>","PeriodicalId":9184,"journal":{"name":"Boreas","volume":"55 2","pages":"422-442"},"PeriodicalIF":2.9,"publicationDate":"2026-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/bor.70034","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147686130","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}