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Glover, Katherine C., Thomas V. Lowell, Gregory C. Wiles, Donald Pair, Patrick Applegate, and Irena Hajdas. "Deglaciation, basin formation and post-glacial climate change from a regional network of sediment core sites in Ohio and eastern Indiana." Quaternary Research 76, no. 3 (November 2011): 401–10. http://dx.doi.org/10.1016/j.yqres.2011.06.004.
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AbstractMany paleoclimate and landscape change studies in the American Midwest have focused on the Late Glacial and early Holocene time periods (~ 16–11 ka), but little work has addressed landscape change in this area between the Last Glacial Maximum and the Late Glacial (~ 22–16 ka). Sediment cores were collected from 29 new lake and bog sites in Ohio and Indiana to address this gap. The basal radiocarbon dates from these cores show that initial ice retreat from the maximal last-glacial ice extent occurred by 22 ka, and numerous sites that are ~ 100 km inside this limit were exposed by 18.9 ka. Post-glacial environmental changes were identified as stratigraphic or biologic changes in select cores. The strongest signal occurs between 18.5 and 14.6 ka. These Midwestern events correspond with evidence to the northeast, suggesting that initial deglaciation of the ice sheet, and ensuing environmental changes, were episodic and rapid. Significantly, these changes predate the onset of the Bølling postglacial warming (14.8 ka) as recorded by the Greenland ice cores. Thus, deglaciation and landscape change around the southern margins of the Laurentide Ice Sheet happened ~ 7 ka before postglacial changes were felt in central Greenland.
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Munroe, Jeffrey S. "Lacustrine records of post-glacial environmental change from the Nulhegan Basin, Vermont, USA." Journal of Quaternary Science 27, no. 6 (June 6, 2012): 639–48. http://dx.doi.org/10.1002/jqs.2557.
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Munroe, Jeffrey S., and Benjamin J. C. Laabs. "Multiproxy lacustrine records of post-glacial environmental change from the Uinta Mountains, Utah, USA." GSA Bulletin 132, no. 1-2 (May 2, 2019): 48–64. http://dx.doi.org/10.1130/b35056.1.
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Abstract Twenty-one sediment cores were obtained from 20 lakes in the Uinta Mountains, Utah, USA. Depth-age models were developed using 14C dating, and sediments were analyzed for loss-on-ignition (LOI), carbon-nitrogen ratio (C:N), and grain size distribution. Although some of these cores have been considered individually in previous studies, here the entire set of cores is evaluated collectively to identify consistent patterns, commonalities, and trends in the post-glacial interval. All lakes accumulated substantially greater amounts of submicron-size clastic material before ca. 9.5 ka BP. This pattern is interpreted as a signal of prolonged landscape instability following deglaciation. Values of LOI and C:N exhibit a strong, positive correlation in nearly all lakes, indicating that organic matter accumulation is controlled by the influx of terrestrial material. In the six lakes exhibiting the strongest correlation, and featuring the most robust inflowing streams, median grain size and the abundance of sand increased between 10 and 6 ka BP, simultaneous with increases in LOI and C:N. This correspondence is interpreted as evidence for frequent high-intensity storms during the early Holocene, likely driven by enhanced monsoonal circulation. The early parts of five of the records contain a sharp increase in LOI. Lakes exhibiting this pattern are typically smaller and shallower, and are located in less rugged watersheds. Finally, all six cores from the western Uinta Mountains contain evidence for an environmental perturbation ca. 4.5 ka BP. Although the nature of this event is unclear, these lakes accumulated notably finer-grained sediment with less organic matter at this time. This analysis illuminates the post-glacial history of this strategically located mountain range, and underscores the value inherent in analyzing cores from multiple lakes when reconstructing paleoclimatic history.
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Walker, James. "The archaeology of climate change in Late and Post-Glacial North-west Europe." Antiquity 94, no. 374 (March 17, 2020): 536–38. http://dx.doi.org/10.15184/aqy.2020.27.
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Climate change regularly made the news in 2019. In the face of numerous protests around the globe, and increasingly frequent natural disasters, we appear to be entering a (perhaps overdue) stage of heightened awareness with regard to the fragility of the Earth and our impact upon it. Current concerns over the fate of our planet, and species, look set to stay, but for deep-time prehistorians, who have long contended with records of environmental change on a scale relatively unparalleled in historic times, business continues as usual. In the opening to Resilience and reorganisation of social systems during the Weichselian Lateglacial in North-west Europe, Sonja Grimm makes reference to the importance of the Club of Rome (a non-profit, non-governmental organisation) in highlighting socio-ecological stability as an issue for public concern, and one that archaeological studies such as this can contribute to and bolster. Meanwhile, Peter Moe Astrup, in his introduction to Sea-level change in Mesolithic southern Scandinavia, notes that Mesolithic people from this area would have been exposed to the consequences of global sea-level rise on a far greater scale than those predicted for our own future generations. What these volumes share is an emphasis on the importance of adaptive flexibility and the human experience in shaping our response to climate change.
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Scuderi, Louis A., and Peter J. Fawcett. "Holocene environmental change resets lichen surface dates on Recess Peak glacial deposits in the Sierra Nevada, California." Quaternary Research 80, no. 2 (September 2013): 180–88. http://dx.doi.org/10.1016/j.yqres.2013.05.009.
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Development of an accurate chronology for glacial deposits in the Sierra Nevada has long been problematic given the lack of suitable organic material for radiocarbon dating. Lichenometry initially appeared promising as ages showed an increase from cirque headwalls to down-canyon moraines. However, while Recess Peak lichen age estimates range from 2 to 3 ka, recent work shows these deposits to be at least 10 ka older. Here, we present evidence for a late Holocene reset of Recess Peak lichen ages by significant post-depositional climate change. Following late-Pleistocene deposition of Recess Peak moraines, warming through the mid-Holocene allowed forests to advance into shallow basins eliminating local inverted tree lines. This produced a partial canopy where shading killed the original post-Pleistocene crustose lichen colonies. Late-Holocene cooling resulted in forest retreat from these basins as alpine tree line fell. Lichens then recolonized the re-exposed Recess Peak deposits. We conclude that while Recess Peak lichen ages are accurate to within the dating uncertainty of the technique, existing lichen ages actually date the timing of post-mid-Holocene cooling and recolonization, and not the original emplacement of these deposits. Thus, applications of Lichenometry should consider post-depositional environmental change when interpreting the meaning of these dates.
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Whitlock, Cathy. "Post Glacial Fire Frequency and its Relation to Longterm Vegetational and Climatic Changes in Yellowstone Park." UW National Parks Service Research Station Annual Reports 14 (January 1, 1990): 187–90. http://dx.doi.org/10.13001/uwnpsrc.1990.2939.
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The paleoecologic record provides unique insights into the response of communities to environmental perturbations of different duration and intensity. Climate is a primary agent of environmental change and its long-term effect on the vegetation of the Yellowstone/Grand Teton region is revealed in a regional network of pollen records. Fire frequency is controlled by climate, and as climate changes, so too does the importance of fire in shaping and maintaining spatial patterns of vegetation. The prehistoric record of Yellowstone's Northern Range, for example, shows the response of vegetation to the absence of major fires in the last 150 years (Whitlock et al. 1991; Engstrom et al. in press). In longer records spanning the last 13,000 years, periods of frequent fires are suggested by sediments containing high percentages of lodgepole pine (Pinus contorta) and Douglas-fir (Pseudotsuga menziesii) and high amounts of charcoal (Barnosky et al. 1987; Whitlock in prep.).
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Dolby, Greer A., Ryan Hechinger, Ryan A. Ellingson, Lloyd T. Findley, Julio Lorda, and David K. Jacobs. "Sea-level driven glacial-age refugia and post-glacial mixing on subtropical coasts, a palaeohabitat and genetic study." Proceedings of the Royal Society B: Biological Sciences 283, no. 1843 (November 30, 2016): 20161571. http://dx.doi.org/10.1098/rspb.2016.1571.
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Using a novel combination of palaeohabitat modelling and genetic mixture analyses, we identify and assess a sea-level-driven recolonization process following the Last Glacial Maximum (LGM). Our palaeohabitat modelling reveals dramatic changes in estuarine habitat distribution along the coast of California (USA) and Baja California (Mexico). At the LGM (approx. 20 kya), when sea level was approximately 130 m lower, the palaeo-shoreline was too steep for tidal estuarine habitat formation, eliminating this habitat type from regions where it is currently most abundant, and limiting such estuaries to a northern and a southern refugium separated by 1000 km. We assess the recolonization of estuaries formed during post-LGM sea-level rise through examination of refugium-associated alleles and approximate Bayesian computation in three species of estuarine fishes. Results reveal sourcing of modern populations from both refugia, which admix in the newly formed habitat between the refuges. We infer a dramatic peak in habitat area between 15 and 10 kya with subsequent decline. Overall, this approach revealed a previously undocumented dynamic and integrated relationship between sea-level change, coastal processes and population genetics. These results extend glacial refugial dynamics to unglaciated subtropical coasts and have significant implications for biotic response to predicted sea-level rise.
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Håkansson, S. "A review of various factors influencing the stable carbon isotope ratio of organic lake sediments by the change from glacial to post-glacial environmental conditions." Quaternary Science Reviews 4, no. 2 (1985): 135–46. http://dx.doi.org/10.1016/0277-3791(85)90017-4.
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Dube, Shiva Kant. "Glacial Lake Outburst Flood in Nepal: A Challenging Environmental Hazard and Disaster." Academic Voices: A Multidisciplinary Journal 4 (March 28, 2015): 56–67. http://dx.doi.org/10.3126/av.v4i0.12360.
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Geographically, Nepal is situated on the lap of the Himalayas occupying 0.3 percent area of Asia and 0.03 percent of the world. Recently, global climate change has invited enormous environmental hazards and disasters in the Hindu-Kush Himalayan region. Catastrophic floods originating from the outburst of glacial lakes have been recognized as one of the primary natural hazards in Nepal, making downstream areas vulnerable. Frequent severe floodscaused by glacier outburst in the Nepal Himalayas, occur once every three years. Nine potentially dangerous glaciers were identified in the Eastern and Central Himalayas during pre- and post-monsoon seasons. At national and international level, Glacial Lake Outburst Floods (GLOF) in Nepal, are receiving considerable attention. Such floods endanger thousands of people, hundreds of villages and basic infrastructure causing disasters. This paper incorporates a case of flash-flood caused by GLOF and torrential rain in India which can be taken as a lesson to mitigate/minimize massive loss of lives and property in the Nepalese context.DOI: http://dx.doi.org/10.3126/av.v4i0.12360Academic Voices Vol.4 2014: 56-67
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Le Hir, G., Y. Goddéris, Y. Donnadieu, and G. Ramstein. "A geochemical modelling study of the evolution of the chemical composition of seawater linked to a global glaciation: implications for life sustainability." Biogeosciences Discussions 4, no. 3 (June 20, 2007): 1839–76. http://dx.doi.org/10.5194/bgd-4-1839-2007.
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Abstract. The Snowball Earth theory initially proposed by Kirschvink (Kirschvink, 1992) to explain the Neoproterozoic glacial episodes, suggested that the Earth was fully ice-covered at 720 My (Sturtian episode) and 640 My (Marinoan episode). This succession of extreme climatic crises induced a stress which is considered as a strong selective pressure on the evolution of life (Hoffman et al., 1998). However recent biological records (Corsetti, 2006) do not support this theory as little change is observed in the diversity of microfossils outcrops before and after the Marinoan glacial interval. In this contribution we address this apparent paradox. Using a numerical model of carbon-alkalinity global cycles, we quantify several environmental stresses caused by a global glaciation. We suggest that during global glaciations, the ocean becomes acidic (pH~6), and unsaturated with respect to carbonate minerals. Moreover the quick transition from ice-house to greenhouse conditions implies an abrupt and large shift of the oceanic surface temperature which causes an extended hypoxia. The intense continental weathering, in the aftermath of the glaciation, deeply affects the seawater composition inducing rapid changes in terms of pH and alkalinity. We also propose a new timing for post glacial perturbations and for the cap carbonates deposition, ~2 Myr instead of 200 kyr as suggested in a previous modelling study. In terms of Precambrian life sustainability, seawater pH modifications appear drastic all along the glaciation, but we show that the buffering action of the oceanic crust dissolution processes avoids a total collapse of biological productivity. In opposite short-lived and large post-glacial perturbations are more critical and may have played a role of environmental filter suggested in the classic snowball Earth theory. Only a permissive life (prokaryotes or simple eukaryotes) may explain the relative continuity in microfossils diversity observed before, during and after Neoproterozoic glaciation events.
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Smelror, Morten, and Dirk Knaust. "Trace fossils and palynomorphs in Holocene calcareous concretions from Lake Selbusjøen, Mid-Norway: Post-glacial environmental records." Holocene 31, no. 5 (January 17, 2021): 732–45. http://dx.doi.org/10.1177/0959683620988046.
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Trace fossils and palynomorphs are recorded for the first time in Holocene calcareous concretions from Lake Selbusjøen, Central Norway. The described trace fossils can be assigned to the Mermia ichnofacies, characterizing lake deposits with good oxygenation and low depositional energy. The predominance of simple grazing trails and shallow burrows (e.g. Cochlichnus, Helminthoidichnites and Treptichnus) in silty and sandy concretions possibly represent relatively low-energy sublittoral parts of the lake, while the occurrence of Vagorichnus and Arenicolites in sandy substrate points to littoral and shallow sublittoral areas with moderate depositional energy. The trace fossils and palynomorph assemblages from Lake Selbusjøen appear to relate to periods of climatic warming during Pre-Boreal times, and possibly also Atlantic times.
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Louis, Marie, Mikkel Skovrind, Jose Alfredo Samaniego Castruita, Cristina Garilao, Kristin Kaschner, Shyam Gopalakrishnan, James S. Haile, et al. "Influence of past climate change on phylogeography and demographic history of narwhals, Monodon monoceros." Proceedings of the Royal Society B: Biological Sciences 287, no. 1925 (April 22, 2020): 20192964. http://dx.doi.org/10.1098/rspb.2019.2964.
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The Arctic is warming at an unprecedented rate, with unknown consequences for endemic fauna. However, Earth has experienced severe climatic oscillations in the past, and understanding how species responded to them might provide insight into their resilience to near-future climatic predictions. Little is known about the responses of Arctic marine mammals to past climatic shifts, but narwhals ( Monodon monoceros ) are considered one of the endemic Arctic species most vulnerable to environmental change. Here, we analyse 121 complete mitochondrial genomes from narwhals sampled across their range and use them in combination with species distribution models to elucidate the influence of past and ongoing climatic shifts on their population structure and demographic history. We find low levels of genetic diversity and limited geographic structuring of genetic clades. We show that narwhals experienced a long-term low effective population size, which increased after the Last Glacial Maximum, when the amount of suitable habitat expanded. Similar post-glacial habitat release has been a key driver of population size expansion of other polar marine predators. Our analyses indicate that habitat availability has been critical to the success of narwhals, raising concerns for their fate in an increasingly warming Arctic.
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SEIJMONSBERGEN, A. C., J. SEVINK, L. H. CAMMERAAT, and J. RECHARTE. "A potential geoconservation map of the Las Lagunas area, northern Peru." Environmental Conservation 37, no. 2 (June 2010): 107–15. http://dx.doi.org/10.1017/s0376892910000408.
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SUMMARYThe Andean páramo ecosystems host geodiversity of global importance, but also have important societal functions, including agricultural production and delivery of water to people and industry. Páramo geo-ecosystems are highly susceptible to environmental degradation because of their alpine relief, extreme climate and fragile soils. In contrast to other parts of the world, geodiversity assessment studies in the Andes are scarce. A geodiversity assessment method was adapted and used to produce a potential geoconservation map of the Andean páramo. The Las Lagunas area (Cajamarca, Northern Peru) has a rich archive of climate proxy data and landscape reconstruction, and plays a key role in the functioning of regional geo-ecosystems. Undisturbed proxies for climate change are contained in four Late-Glacial recessional complexes of its former local ice cap and in pollen records preserved in the post-glacial peat cover. These new findings were used to develop a refined chronostratigraphy of the Late-Glacial warming period in the Andes of Northern Peru. Geo-ecosystem functions (for example water and carbon storage) depend on the environmental vulnerability and disturbance of the landforms and deposits. Therefore, potential geoconservation areas that combine a high scientific value and environmental vulnerability with a low disturbance and low frequency of occurrence should be prioritized for geoconservation. Such a strategy should also optimize sustainable use of resources and development of these areas. Mountainous countries like Peru require future management strategies that recognize and incorporate potential geoconservation information in regional planning, to prevent unnecessary loss of irreplaceable soils, climate proxies and geo-ecosystem functions upon future changes in land use and climate.
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Paull, Tara M., Sarah A. Finkelstein, and Konrad Gajewski. "Interactions between climate and landscape drive Holocene ecological change in a High Arctic lake on Somerset Island, Nunavut, Canada." Arctic Science 3, no. 1 (March 1, 2017): 17–38. http://dx.doi.org/10.1139/as-2016-0013.
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This study presents a diatom-based analysis of the post-glacial Holocene environmental history at Lake RS29 on Somerset Island in the Canadian High Arctic. Earliest post-glacial diatom assemblages (10 200–10 000 cal yr BP) consisted mainly of small, benthic fragilarioid taxa. Poor diatom preservation in the early Holocene (~10 000–6200 cal yr BP) is associated with warm conditions, as determined by pollen data from the same core and other paleoclimate estimates from the region. Analysis of this and other sites from across the Canadian Arctic suggest that zones of poor diatom preservation or diatom absence in lake sediment records may be associated with warm conditions. After 6200 cal yr BP, acidophilic assemblages consisting of Aulacoseira spp. and a suite of periphytic taxa indicate acidification since the mid-Holocene. During this time period, cooling causing changes in lake ice phenology was likely a major driver of the reconstructed mid-Holocene pH decline. Watershed processes, including reduced fluxes of base cations as the rate of sediment accumulation slowed, may also be contributors to long-term shifts in lake water pH and associated changes in diatom assemblages. The uppermost sediments in the Lake RS29 record were characterized by abrupt declines in Aulacoseira alpigena and increases in benthic diatom taxa Cyclotella sensu lato, suggesting an increase in lake water pH and longer ice-free seasons.
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Leavitt, S. W., and S. R. Danzer. "δ13C Variations in C3 Plants Over the Past 50,000 Years." Radiocarbon 34, no. 3 (1992): 783–91. http://dx.doi.org/10.1017/s0033822200064080.
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We examined three sets of data to determine if there are consistent changes in δ13C of C3 plants through time, under the hypothesis that environmental changes from glacial to postglacial may have caused such isotopic changes over the last 50 ka. The records of δ13C change in all types of plant data from Radiocarbon and from the University of Arizona Radiocarbon Laboratory archives both reveal significant decline of 0.8–1.0‰ in δ13C from pre- to post-10 ka BP averages. The δ13C of wood data alone from Radiocarbon shows a larger significant decline of 3.0‰, and twigs, leaves and Juniperus categories from the Arizona data individually show declines of 0.4–1.44‰. Peat and charcoal from both data sets show no significant mean δ13C differences. A highly constrained set of wood samples from the Great Lakes region spanning the last 12 ka show isotopic changes of ca. 3‰, but most of that variation apparently does not reflect global environmental changes.
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Neil, Karen, Konrad Gajewski, and Matthew Betts. "Human-ecosystem interactions in relation to Holocene environmental change in Port Joli Harbour, southwestern Nova Scotia, Canada." Quaternary Research 81, no. 2 (March 2014): 203–12. http://dx.doi.org/10.1016/j.yqres.2014.01.001.
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AbstractA high-resolution pollen record from Path Lake in Port Joli Harbour, Nova Scotia, Canada, provides a paleo-ecological perspective on Holocene climate and vegetation variability within the context of local archaeological research. Pollen assemblages in the early Holocene reflect a post-glacial forest dominated by Pinus, Tsuga, Betula and Quercus. During this time, a lower frequency of radiocarbon dated cultural material suggests lower human settlement intensity. Shallow water aquatic (Isoetes) and wetland (Alnus, Sphagnum) taxa increased after 3400 cal yr BP in response to a transition towards wetter climatic conditions. Culturally significant periods, where settlement intensity increased in the Maritimes and Maine, coincide with maximum values of reconstructed total annual precipitation, suggesting that environmental conditions may have influenced prehistoric human activity. European settlement, after 350 cal yr BP, was marked by a rise in Ambrosia. The impact of anthropogenic fire disturbances on the landscape was evidenced by peak charcoal accumulations after European settlement.
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Groom, Scott V. C., Mark I. Stevens, and Michael P. Schwarz. "Parallel responses of bees to Pleistocene climate change in three isolated archipelagos of the southwestern Pacific." Proceedings of the Royal Society B: Biological Sciences 281, no. 1785 (June 22, 2014): 20133293. http://dx.doi.org/10.1098/rspb.2013.3293.
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The impacts of glacial cycles on the geographical distribution and size of populations have been explored for numerous terrestrial and marine taxa. However, most studies have focused on high latitudes, with only a few focused on the response of biota to the last glacial maximum (LGM) in equatorial regions. Here, we examine how population sizes of key bee fauna in the southwest Pacific archipelagos of Fiji, Vanuatu and Samoa have fluctuated over the Quaternary. We show that all three island faunas suffered massive population declines, roughly corresponding in time to the LGM, followed by rapid expansion post-LGM. Our data therefore suggest that Pleistocene climate change has had major impacts across a very broad tropical region. While other studies indicate widespread Holarctic effects of the LGM, our data suggest a much wider range of latitudes, extending to the tropics, where these climate change repercussions were important. As key pollinators, the inferred changes in these bee faunas may have been critical in the development of the diverse Pacific island flora. The magnitude of these responses indicates future climate change scenarios may have alarming consequences for Pacific island systems involving pollinator-dependent plant communities and agricultural crops.
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Mullins, Henry T., and John D. Halfman. "High-Resolution Seismic Reflection Evidence for Middle Holocene Environmental Change, Owasco Lake, New York." Quaternary Research 55, no. 3 (May 2001): 322–31. http://dx.doi.org/10.1006/qres.2001.2232.
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AbstractApproximately 70 km of new decimeter-resolution seismic reflection profile data from Owasco Lake, New York define a middle Holocene (∼4600 14C yr B.P.) erosion surface in the north end of the lake at water depths as great as 26 m. Beneath the lake, post-glacial sediments are up to 9 m thick and represent about 10% of the total sediment fill. Early to middle Holocene sediments, ∼6 m thick, contain biogenic gas at the south end of the basin and a large (4 km × 300 m × 15 m) subaqueous slide deposit along the east-central portion of the lake. Late Holocene sediments are thinner or absent, particularly at the north end of the lake. The middle Holocene erosion surface may have been produced by a drop in lake level. Alternatively, it may represent a change in climate during the transition between the relatively warm Holocene hypsithermal and cool neoglacial. At this time (∼4600 14C yr B.P.) circulation in Owasco Lake appears to have evolved from sluggish to active. The increased circulation, which persists today, probably resulted from atmospheric cold fronts with strong southwesterly winds that piled up water at the north end of the lake. The increased water circulation may have been ultimately driven by decreasing insolation, which produced an increased pole-to-equator thermal gradient and thus, stronger global winds that began at the transition between the hypsithermal and neoglacial.
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Seppä, Heikki, and K. D. Bennett. "Quaternary pollen analysis: recent progress in palaeoecology and palaeoclimatology." Progress in Physical Geography: Earth and Environment 27, no. 4 (December 2003): 548–79. http://dx.doi.org/10.1191/0309133303pp394oa.
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During the last decade Quaternary pollen analysis has developed towards improved pollen-taxonomical precision, automated pollen identification and more rigorous definition of pollen assemblage zones. There have been significant efforts to model the spatial representation of pollen records in lake sediments which is important for more precise interpretation of the pollen records in terms of past vegetation patterns. We review the difficulties in matching modelled post-glacial plant migration patterns with pollen-based palaeorecords and discuss the potential of DNA analysis of pollen to investigate the ancestry and past migration pathways of the plants. In population ecology there has been an acceleration of the widely advocated conceptual advance of pollen-analytical research from vaguely defined ‘environmental reconstructions’ towards investigating more precisely defined ecological problems aligned with the current ecological theories. Examples of such research have included an increasing number of investigations about the ecological impacts of past disturbances, often integrating pollen records with other palaeoecological data. Such an approach has also been applied to incorporate a time perspective to the questions of ecosystem restoration, nature conservation and forest management. New lines of research are the use of pollen analysis to study long-term patterns of vegetation diversity, such as the role of glacial-age vegetation fragmentation as a cause of Amazonian rain forest diversity, and to investigate links between pollen richness and past plant diversity. Palaeoclimatological use of pollen records has become more quantitative and has included more precise and rigorous testing of pollen-climate calibration models with modern climate data. These tests show the approximate nature of the models and warn against a too straightforward climatic interpretation of the small-scale variation in reconstructions. Pollen-based climate reconstructions over the Late Glacial-early Holocene boundary have indicated that pollen-stratigraphical changes have been rapid with no evidence for response lags. This does not rule out the possibility of migrational disequilibrium, however, as the rapid changes may be mostly due to nonmigrational responses of existing vegetation. It is therefore difficult to assess whether the amplitude of reconstructed climate change reflects real climate change. Other outstanding problems remain the obscure relationship of pollen production and climate, the role of human impact and other nonclimatic factors, and nonanalogue situations.
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Hayles, Simon, Tom Al, Jack Cornett, Alex Harrison, and Jiujiang Zhao. "Growth rates for freshwater ferromanganese concretions indicate regional climate change in eastern Canada at the Northgrippian-Meghalayan boundary." Holocene 31, no. 8 (April 27, 2021): 1250–63. http://dx.doi.org/10.1177/09596836211011652.
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The existence of freshwater ferromanganese concretions has been known for decades, but we are not aware of a generally accepted explanation for their formation, and there has been little research into their potential use as records of Holocene climate and paleohydrology. A conceptual model is presented to describe the environmental and geochemical processes which result in the formation and growth of freshwater ferromanganese concretions. In order to evaluate their potential as historical geochemical records, a concretion from Magaguadavic Lake, New Brunswick, Canada is the focus of a detailed geochronological and geochemical investigation. The radiocarbon data provide a coherent growth curve and a maximum age for the concretion of 8448 ± 43 years, consistent with the establishment of Magaguadavic Lake as a stable post-glacial lacustrine system. The data suggest accretion rates of 1.5 and 3.4 mm per 1000 years during the Northgrippian and Meghalayan stages of the Holocene, respectively. The abrupt change in growth rate observed at the stage boundary may be an indicator of Holocene climate change. These features are consistent with inferences from previous research that warmer climate in the Northgrippian led to eutrophication in some lakes in eastern North America. The results confirm that freshwater Fe–Mn concretions may yield important information about past climatic and environmental conditions.
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Tõnno, Ilmar, Liisi Talas, Rene Freiberg, Anu Kisand, Simon Belle, Normunds Stivrins, Tiiu Alliksaar, Atko Heinsalu, Siim Veski, and Veljo Kisand. "Environmental drivers and abrupt changes of phytoplankton community in temperate lake Lielais Svētiņu, Eastern Latvia, over the last Post-Glacial period from 14.5 kyr." Quaternary Science Reviews 263 (July 2021): 107006. http://dx.doi.org/10.1016/j.quascirev.2021.107006.
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Urrego, Dunia H., Henry Hooghiemstra, Oscar Rama-Corredor, Belen Martrat, Joan O. Grimalt, Lonnie Thompson, Mark B. Bush, et al. "Millennial-scale vegetation changes in the tropical Andes using ecological grouping and ordination methods." Climate of the Past 12, no. 3 (March 21, 2016): 697–711. http://dx.doi.org/10.5194/cp-12-697-2016.
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Abstract. We compare eight pollen records reflecting climatic and environmental change from northern and southern sites in the tropical Andes. Our analysis focuses on the last 30 000 years, with particular emphasis on the Pleistocene to Holocene transition. We explore ecological grouping and downcore ordination results as two approaches for extracting environmental variability from pollen records. We also use the records of aquatic and shoreline vegetation as markers for lake level fluctuations and moisture availability. Our analysis focuses on the signature of millennial-scale climate variability in the tropical Andes, in particular Heinrich stadials (HS) and Greenland interstadials (GI). The pollen records show an overall warming trend during the Pleistocene–Holocene transition, but the onset of post-glacial warming differs in timing among records. We identify rapid responses of the tropical vegetation to millennial-scale climate variability. The signatures of HS and the Younger Dryas are generally recorded as downslope upper forest line (UFL) migrations in our transect, and are likely linked to air temperature cooling. The GI1 signal is overall comparable between northern and southern records and indicates upslope UFL migrations and warming in the tropical Andes. Our marker for lake level changes indicated a north-to-south difference that could be related to moisture availability. The air temperature signature recorded by the Andean vegetation was consistent with millennial-scale cryosphere and sea surface temperature changes but suggests a potential difference between the magnitude of temperature change in the ocean and the atmosphere. We also show that arboreal pollen percentage (AP %) and detrended correspondence analysis (DCA) scores are two complementary approaches to extract environmental variability from pollen records.
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Loboda, Sarah, and Christopher M. Buddle. "Small to large-scale patterns of ground-dwelling spider (Araneae) diversity across northern Canada." FACETS 3, no. 1 (October 1, 2018): 880–95. http://dx.doi.org/10.1139/facets-2018-0007.
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We examined how Arctic spider (Araneae) biodiversity is distributed at multiple spatial scales in northern Canada using a standardized hierarchical sampling design. We investigated which drivers, environmental or spatial, influence the patterns observed. Spatial patterns of Arctic spider species richness and composition were assessed in 12 sites located in arctic, subarctic, and north boreal ecoclimatic regions, spanning 30 degrees of latitude and 80 degrees of longitude. Variation in diversity was partitioned in relation to multiple environmental and spatial drivers of diversity patterns. Over 23 000 adult spiders, representing 306 species in 14 families, were collected in northern Canada, with 107 species (35% of the total species collected) representing new territorial or provincial records. Spider diversity was structured at the regional scale across ecoclimatic regions but was not structured with latitude. Longitudinal patterns of spider diversity across Canada may be explained by post-glacial dispersal. At local scales, diversity was non-randomly distributed and possibly limited by biotic interactions. We recommend the use of ecoclimatic regions as a framework for conservation of biodiversity in northern Canada and spiders as useful bioindicators that can help us understand the effects of climate change across ecoclimatic regions of northern Canada.
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Kadereit, A., and G. A. Wagner. "Geochronological reconsideration of the eastern European key loess section at Stayky in Ukraine." Climate of the Past 10, no. 2 (April 24, 2014): 783–96. http://dx.doi.org/10.5194/cp-10-783-2014.
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Abstract. Event-stratigraphical correlations between regional terrestrial sedimentary archives and marine or ice-core records that provide climate history are highly desirable for a deeper understanding of the effects of global climate change. However, such correlations are not simple, as the terrestrial records tend to be floating and fragmentary, and usually show varying sedimentation rates. Therefore, a reliable chronometric framework is a prerequisite for any event stratigraphy involving terrestrial archives. We propose that the age model underlying the event-stratigraphical approach for the eastern European key loess section at Stayky in Ukraine needs revision. Here we explore why it is unlikely that the Middle Pleniglacial Vytachiv Soil developed during Greenland interstadial (GIS) 8, and why the embryonic soils in the upper part of the Upper Pleniglacial part of the loess section most likely post-date the Heinrich 2 event. As a consequence, the revised age-model challenges the earlier suggested correlation of the suite of incipient soils above the Vytachiv Soil with Greenland Interstadials, which was supposed to start with GIS7 but for which matching from after GIS5 seems more likely. The revised chronology suggests that the transition from Middle to Upper Pleniglacial environmental conditions at the eastern European key section occurred during the final phase of marine isotope stage (MIS) 3. Thus, the picture appears to be in accordance with that of the western European key section at Nussloch. This points to a common driver of palaeo-environmental change in both regions, such as early late glacial maximum (LGM) advances of the Arctic ice shield or changes of the North Atlantic circulation and sea-ice distribution associated with changes in the palaeowind field relevant to aeolian loess deposition and soil formation. To test and substantiate the alternative age model, more chronologies for well-stratified loess sections throughout the European loess belt are required.
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Kadereit, A., and G. A. Wagner. "Geochronological reconsiderations for the Eastern European key loess section at Stayky in Ukraine." Climate of the Past Discussions 9, no. 3 (May 22, 2013): 2629–59. http://dx.doi.org/10.5194/cpd-9-2629-2013.
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Abstract. Event-stratigraphical correlations between local/regional terrestrial sedimentary archives and marine or ice-core records providing the global climate history and time-scale are highly desirable for a deeper understanding of the effects of global climate change on a local/regional (palaeo-)environment. However, such correlations are not trivial, as the terrestrial records tend to be floating and fragmentary and usually show varying sedimentation rates. Therefore, a reliable chronometric framework is a necessary prerequisite for any event-stratigraphy involving terrestrial archives. In this respect, the age-model underlying the event-stratigraphical approach for the Eastern European key loess section at Stayky in Ukraine appears to need revision. Here we explain, why it is highly unlikely that the Middle Pleniglacial Vytachiv Soil developed during Greenland interstadial (GIS) 8, and why the embryonic soils in the upper part of the Upper Pleniglacial part of the loess section most likely post-date Heinrich 2 event. As a consequence, the revised age-model challenges the earlier suggested correlation of the suite of incipient soils above the Vytachiv Soil with Greenland Interstadials, which was supposed to start with GIS7 but for which matching from after GIS5 seems more likely. The revised chronology suggests that the transition from Middle to Upper Pleniglacial environmental conditions at the Eastern European key section occurred during the final phase of marine isotope stage (MIS) 3. Thus, the picture appears to be in accordance with that of the Western European key section at Nussloch in Germany pointing to a common driver of palaeo-environmental change in both regions, such as early Late Glacial Maximum (LGM) advances of the Arctic ice-shield or changes of the North Atlantic circulation and sea-ice distribution leading also to relevant changes of the palaeowind field.
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Vuillemin, Aurèle, Daniel Ariztegui, Peter R. Leavitt, and Lynda Bunting. "Recording of climate and diagenesis through sedimentary DNA and fossil pigments at Laguna Potrok Aike, Argentina." Biogeosciences 13, no. 8 (April 27, 2016): 2475–92. http://dx.doi.org/10.5194/bg-13-2475-2016.
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Abstract. Aquatic sediments record past climatic conditions while providing a wide range of ecological niches for microorganisms. In theory, benthic microbial community composition should depend on environmental features and geochemical conditions of surrounding sediments, as well as ontogeny of the subsurface environment as sediment degraded. In principle, DNA in sediments should be composed of ancient and extant microbial elements persisting at different degrees of preservation, although to date few studies have quantified the relative influence of each factor in regulating final composition of total sedimentary DNA assemblage. Here geomicrobiological and phylogenetic analyses of a Patagonian maar lake were used to indicate that the different sedimentary microbial assemblages derive from specific lacustrine regimes during defined climatic periods. Two climatic intervals (Mid-Holocene, 5 ka BP; Last Glacial Maximum, 25 ka BP) whose sediments harbored active microbial populations were sampled for a comparative environmental study based on fossil pigments and 16S rRNA gene sequences. The genetic assemblage recovered from the Holocene record revealed a microbial community displaying metabolic complementarities that allowed prolonged degradation of organic matter to methane. The series of Archaea identified throughout the Holocene record indicated an age-related stratification of these populations brought on by environmental selection during early diagenesis. These characteristics were associated with sediments resulting from endorheic lake conditions and stable pelagic regime, high evaporative stress and concomitant high algal productivity. In contrast, sulphate-reducing bacteria and lithotrophic Archaea were predominant in sediments dated from the Last Glacial Maximum, in which pelagic clays alternated with fine volcanic material characteristic of a lake level highstand and freshwater conditions, but reduced water column productivity. Comparison of sedimentary DNA composition with that of fossil pigments suggested that post-depositional diagenesis resulted in a rapid change in the initial nucleic acid composition and overprint of phototrophic communities by heterotrophic assemblages with preserved pigment compositions. Long DNA sequences (1400–900 bp) appeared to derive from intact bacterial cells, whereas short fragments (290–150 bp) reflected extracellular DNA accumulation in ancient sediments. We conclude that sedimentary DNA obtained from lacustrine deposits provides essential genetic information to complement paleoenvironmental indicators and trace post-depositional diagenetic processes over tens of millennia. However, it remains difficult to estimate the time lag between original deposition of lacustrine sediments and establishment of the final composition of the sedimentary DNA assemblage.
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Byrne, Tomás, Niall Farrelly, Colin Kelleher, Trevor R. Hodkinson, Stephen L. Byrne, and Susanne Barth. "Genetic Diversity and Structure of a Diverse Population of Picea sitchensis Using Genotyping-by-Sequencing." Forests 13, no. 9 (September 17, 2022): 1511. http://dx.doi.org/10.3390/f13091511.
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Picea sitchensis, Sitka spruce, is of interest to forestry as both a conservation species and a highly productive crop. Its native range stretches from Alaska to California, and it is hence distributed across a large environmental cline with areas of local adaptation. The IUFRO collection, established in 1968–1970, consists of 81 provenances of commercial and scientific interest spanning this native range. We used genotyping-by-sequencing on 1177 genotypes, originating from 80 of the IUFRO provenances which occupy 19 geographic regions of the Pacific Northwest, resulting in an SNP database of 36,567 markers. We detected low levels of genetic differentiation across this broad environmental cline, in agreement with other studies. However, we discovered island effects on geographically distant populations, such as those on Haida Gwaii and Kodiak Island. Using glaciation data, alongside this database, we see apparent post-glacial recolonization of the mainland from islands and the south of the range. Genotyping the IUFRO population expands upon the use of the collection in three ways: (i) providing information to breeders on genetic diversity which can be implemented into breeding programs, optimizing genetic gain for important traits; (ii) serving a scientific resource for studying spruce species; and (iii) utilizing provenances in breeding programs which are more tolerant to climate change.
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Akers, Pete D., Joël Savarino, Nicolas Caillon, Olivier Magand, and Emmanuel Le Meur. "Photolytic modification of seasonal nitrate isotope cycles in East Antarctica." Atmospheric Chemistry and Physics 22, no. 24 (December 14, 2022): 15637–57. http://dx.doi.org/10.5194/acp-22-15637-2022.
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Abstract. Nitrate in Antarctic snow has seasonal cycles in nitrogen and oxygen isotopic ratios that reflect its sources and atmospheric formation processes, and as a result, nitrate archived in Antarctic ice should have great potential to record atmospheric chemistry changes over thousands of years. However, sunlight that strikes the snow surface results in photolytic nitrate loss and isotopic fractionation that can completely obscure the nitrate's original isotopic values. To gain insight into how photolysis overwrites the seasonal atmospheric cycles, we collected 244 snow samples along an 850 km transect of East Antarctica during the 2013–2014 CHICTABA traverse. The CHICTABA route's limited elevation change, consistent distance between the coast and the high interior plateau, and intermediate accumulation rates offered a gentle environmental gradient ideal for studying the competing pre- and post-depositional influences on archived nitrate isotopes. We find that nitrate isotopes in snow along the transect are indeed notably modified by photolysis after deposition, and drier sites have more intense photolytic impacts. Still, an imprint of the original seasonal cycles of atmospheric nitrate isotopes is present in the top 1–2 m of the snowpack and likely preserved through archiving in glacial ice at these sites. Despite this preservation, reconstructing past atmospheric values from archived nitrate in similar transitional regions will remain a difficult challenge without having an independent proxy for photolytic loss to correct for post-depositional isotopic changes. Nevertheless, nitrate isotopes should function as a proxy for snow accumulation rate in such regions if multiple years of deposition are aggregated to remove the seasonal cycles, and this application can prove highly valuable in its own right.
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Vuillemin, A., D. Ariztegui, P. R. Leavitt, and L. Bunting. "Recording of climate and diagenesis through fossil pigments and sedimentary DNA at Laguna Potrok Aike, Argentina." Biogeosciences Discussions 12, no. 22 (November 16, 2015): 18345–88. http://dx.doi.org/10.5194/bgd-12-18345-2015.
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Abstract. Aquatic sediments record past climatic conditions while providing a wide range of ecological niches for microorganisms. Although marine sedimentary microbial assemblages are often defined by their surrounding geochemical conditions, the influence of environmental features upon microbial development and post-depositional survival remains largely unknown in the lacustrine realm. Due to long-term microbial activity, the composition of environmental DNA can be expected to evolve with sediment depth and over time and therefore should reflect both ancient and extant microbial populations, but this hypothesis has rarely been tested using a multiproxy approach. Here geomicrobiological and phylogenetic analyses of a Patagonian maar lake were used to indicate that the different sedimentary microbial assemblages derive from specific lacustrine regimes during defined climatic periods. Two well defined climatic intervals whose sediments harboured active microbial populations and measurable ATP were sampled for a comparative environmental study based on fossil pigments and 16S rRNA gene sequences. Bacterial and archaeal 16S rRNA gene sequences recovered from the Holocene record revealed a microbial community adapted to subsaline conditions actively producing methane during organic matter degradation. These characteristics were associated with sediments resulting from endorheic lake conditions with high evaporative stress and concomitant high algal productivity. Moreover, archaeal clone libraries established throughout the Holocene record indicate an age-related stratification of these populations, consistent with a gradual use of organic substrates after deposition. In contrast, sulphate-reducing bacteria and lithotrophic Archaea were predominant in sediments dated from the Last Glacial Maximum, in which pelagic clays alternated with fine volcanic material characteristic of a lake level highstand and freshwater conditions, but reduced water column productivity. These patterns reveal that microbial assemblages identified from environmental DNA stemmed from a variety of sedimentary niches associated with climate-dependent factors (catchment inflows, water column conditions, productivity), but that initial assemblages underwent structural changes and selective preservation during early diagenesis to result in the final composition entombed in the sediments. We conclude that environmental DNA obtained from lacustrine sediments provides essential genetic information to complement paleoenvironmental indicators and trace climate change and post-depositional diagenetic processes over tens of millennia.
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Bourgeois-Roy, Andréanne, Hugo Crites, Pascal Bernatchez, Denis Lacelle, and André Martel. "Abrupt mortality of marine invertebrates at the Younger Dryas-Holocene transition in a shallow inlet of the Goldthwait Sea." Holocene 28, no. 12 (September 10, 2018): 1894–908. http://dx.doi.org/10.1177/0959683618798130.
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The late Pleistocene–early Holocene transition period was characterized by rapid environmental change. Here, we investigate the impact of these changes on the marine invertebrates living in a shallow inlet of the post-glacial Goldthwait Sea. The site is located near Baie-Comeau (QC, Canada), where a number of remarkably well-preserved shell deposits are found along the Rivière aux Anglais Valley on the north shore of the St. Lawrence maritime estuary. Seven phyla of marine invertebrates with a minimum of 25 species or taxa were inventoried in a shell deposit, dominated by a community of Hiatella arctica with Mytilus edulis and barnacles composing the subcommunity. The majority of taxa identified in the shell deposit are boreal and sub-Arctic species; however, temperate species that exist today in the St. Lawrence maritime estuary have not been found. Based on marine invertebrate diversity and δ18O(CaCO3) of Mytilus edulis, the water in the shallow inlet of the Goldthwait Sea must have been cold and saline. The range of AMS 14C ages from 15 Mytilus edulis, constrained to 10,900 and 10,690 cal. yr BP, and exceptional state of preservation of adult and juvenile molluscan specimens suggest the abrupt mortality of entire invertebrate communities due to changing hydrodynamic conditions that included the combined effect of freshwater discharge from the receding Laurentide Ice Sheet and rapid isostatic uplift.
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Peti, Leonie, and Paul C. Augustinus. "Micro-XRF-inferred depositional history of the Orakei maar lake sediment sequence, Auckland, New Zealand." Journal of Paleolimnology 67, no. 4 (February 7, 2022): 327–44. http://dx.doi.org/10.1007/s10933-022-00235-y.
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AbstractLake sediment records offer insights into past climate and environmental changes. There are, however, few continuous lake sediment records from the Southern Hemisphere mid-latitudes that span the last glacial interval (LGI) and have the requisite chronological control and sampling resolution. Orakei maar paleolake in the Auckland Volcanic Field, New Zealand, is an exception, as it contains a high-resolution record of continuous lacustrine sedimentation from its formative phreatomagmatic eruption ~ 130 ka, until post-glacial sea-level rise breached the crater tuff rim and connected the lake to the sea ~ 9 ka. We used micro-XRF core scanning, dry bulk density, loss-on-ignition and visual facies descriptions to investigate the depositional history of Orakei maar lake as a response to regional and global drivers of climate change, and to erosional events in the lake catchment. The climate history of the lake was divided into six depositional phases: (I) Early warming with frequent in-wash events, followed by climate fluctuations coeval with marine isotope stages (MIS) 5e to mid-5c, (II) Warm, quiescent depositional conditions during mid-MIS 5c to 5a, (III) A colder, windier interval during MIS 4, (IV) Warmer conditions with dominantly autochthonous sedimentation during MIS 3, (V) Cold conditions followed by a slow temperature increase and the onset of sea-level rise during late MIS 2, (VI) Warm conditions that culminated in formation of a peat unit at the top of the Orakei lacustrine sediment sequence, which was terminated by an influx of massive marine muds into the basin at 9.75 ka. Comparison of the inferred climate evolution at Orakei with climate inferences from the global marine benthic MIS record during LGI shows general agreement, though inferred climate changes consistently occur earlier at Orakei than in the MIS. There is also general agreement in temperature changes inferred from the Orakei record and from other regional lake sediment records, but more detailed comparison requires additional proxy climate data such as pollen, organic geochemistry and biomarkers, to better understand discrepancies between some records. This study demonstrated the great potential of the Orakei record for paleoclimate inference and the applicability of micro-XRF core scanning data for addressing questions about paleoclimate and paleoenvironment. It also highlighted past intervals that require further study.
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Rossi, Veronica, Alessandro Amorosi, Giulia Barbieri, Stefano Claudio Vaiani, Matteo Germano, and Bruno Campo. "A Long-Term Record of Quaternary Facies Patterns and Palaeonvironmental Trends from the Po Plain (NE Italy) as Revealed by Bio-Sedimentary Data." Geosciences 11, no. 10 (September 23, 2021): 401. http://dx.doi.org/10.3390/geosciences11100401.
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Understanding Quaternary dynamics of delta-coastal plains across multiple glacial-interglacial cycles in the Milankovitch band (~100 kyrs) is crucial to achieve a robust evaluation of possible environmental response to future climate-change scenarios. In this work, we document the long-term bio-sedimentary record of core 204 S16 (~205 m long), which covers a wide portion of the post-MPR (Mid-Pleistocene Revolution) interval, taking advantage of the highly subsiding context of the SE Po Plain (NE Italy). Detailed facies characterization through an integrated sedimentological and meiofauna (benthic foraminifers and ostracods) approach allowed for the identification of a repetitive pattern of alluvial deposits alternating with four fossiliferous, paralic to shallow-marine units (Units 1–4). The transgressive surfaces identified at the base of these units mark major flooding events, forced by Holocene (Unit 4), Late Pleistocene (Unit 3) and Middle Pleistocene (Units 1, 2) interglacials. Distinct stratigraphic patterns typify the Middle Pleistocene interval, which includes coastal-marine (tidal inlet and bay) deposits. In contrast, lagoonal sediments record the maximum marine influence in the Late Pleistocene-Holocene succession. As a whole, the meiofauna tracks a regressive trend, with the deepest conditions recorded by the oldest Unit 1 (MIS 9/11 age?).
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Bastos, Alex C., Claudia G. Vilela, Valéria S. Quaresma, and Fabiana K. Almeida. "Mid- to Late-Holocene estuarine infilling processes studied by radiocarbon dates, high resolution seismic and biofacies at Vitoria Bay, Espirito Santo, Southeastern Brazil." Anais da Academia Brasileira de Ciências 82, no. 3 (September 2010): 761–70. http://dx.doi.org/10.1590/s0001-37652010000300022.
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Vitoria Bay is a 20 km long estuary, morphologically narrow, with a microtidal regime and, as other modern estuaries, was formed during the last post-glacial transgression. The estuarine bed morphology is characterised by a main natural channel limited by tidal flats with developed mangroves. Original radiocarbon dates were obtained for the site. Five radiocarbon ages ranging from 1,010 to 7,240 years BP were obtained from two sedimentary cores, which represent a 5 m thick stratigraphic sequence. The results indicate that, until about 4,000 cal. yrs BP, environmental conditions in Vitoria Bay were still of an open bay, with a free and wide connection with marine waters. During the last 4,000 yrs, the bay has experienced a major regression phase, by becoming more restricted in terms of seawater circulation and probably increasing tidal energy. Three main stratigraphic surfaces were recognised, which limit trangressive, trangressive/highstand and regressive facies. The present channel morphology represents a tidal scouring surface or a tidal diastem, which erodes and truncates regressive facies bedding. Foraminiferal biofacies, which change from marine to brackish and mangrove tidal-flat environments, support the seismic stratigraphic interpretation. Absence of mangrove biofacies at one of the two cores is also an indication of modern tidal ravinement.
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Liphardt, Schuyler W., Hae Ji Kang, Laurie J. Dizney, Luis A. Ruedas, Joseph A. Cook, and Richard Yanagihara. "Complex History of Codiversification and Host Switching of a Newfound Soricid-Borne Orthohantavirus in North America." Viruses 11, no. 7 (July 11, 2019): 637. http://dx.doi.org/10.3390/v11070637.
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Orthohantaviruses are tightly linked to the ecology and evolutionary history of their mammalian hosts. We hypothesized that in regions with dramatic climate shifts throughout the Quaternary, orthohantavirus diversity and evolution are shaped by dynamic host responses to environmental change through processes such as host isolation, host switching, and reassortment. Jemez Springs virus (JMSV), an orthohantavirus harbored by the dusky shrew (Sorex monticola) and five close relatives distributed widely in western North America, was used to test this hypothesis. Total RNAs, extracted from liver or lung tissue from 164 shrews collected from western North America during 1983–2007, were analyzed for orthohantavirus RNA by reverse transcription polymerase chain reaction (RT-PCR). Phylogenies inferred from the L-, M-, and S-segment sequences of 30 JMSV strains were compared with host mitochondrial cytochrome b. Viral clades largely corresponded to host clades, which were primarily structured by geography and were consistent with hypothesized post-glacial expansion. Despite an overall congruence between host and viral gene phylogenies at deeper scales, phylogenetic signals were recovered that also suggested a complex pattern of host switching and at least one reassortment event in the evolutionary history of JMSV. A fundamental understanding of how orthohantaviruses respond to periods of host population expansion, contraction, and secondary host contact is the key to establishing a framework for both more comprehensive understanding of orthohantavirus evolutionary dynamics and broader insights into host–pathogen systems.
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Rey, Fabian, Erika Gobet, Christoph Schwörer, Albert Hafner, Sönke Szidat, and Willy Tinner. "Climate impacts on vegetation and fire dynamics since the last deglaciation at Moossee (Switzerland)." Climate of the Past 16, no. 4 (July 28, 2020): 1347–67. http://dx.doi.org/10.5194/cp-16-1347-2020.
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Abstract. Since the Last Glacial Maximum (LGM; end ca. 19 000 cal BP) central European plant communities have been shaped by changing climatic and anthropogenic disturbances. Understanding long-term ecosystem reorganizations in response to past environmental changes is crucial to draw conclusions about the impact of future climate change. So far, it has been difficult to address the post-deglaciation timing and ecosystem dynamics due to a lack of well-dated and continuous sediment sequences covering the entire period after the LGM. Here, we present a new paleoecological study with exceptional chronological time control using pollen, spores and microscopic charcoal from Moossee (Swiss Plateau, 521 m a.s.l.) to reconstruct the vegetation and fire history over the last ca. 19 000 years. After lake formation in response to deglaciation, five major pollen-inferred ecosystem rearrangements occurred at ca. 18 800 cal BP (establishment of steppe tundra), 16 000 cal BP (spread of shrub tundra), 14 600 cal BP (expansion of boreal forests), 11 600 cal BP (establishment of the first temperate deciduous tree stands composed of, e.g., Quercus, Ulmus, Alnus) and 8200 cal BP (first occurrence of mesophilous Fagus sylvatica trees). These vegetation shifts were caused by climate changes at ca. 19 000, 16 000, 14 700, 11 700 and 8200 cal BP. Vegetation responses occurred with no apparent time lag to climate change when the mutual chronological uncertainties are considered. This finding is in agreement with further evidence from southern and central Europe and might be explained by the proximity to the refugia of boreal and temperate trees (<400 km) and rapid species spreads. Our palynological record sets the beginning of millennial-scale land use with periodically increased fire and agricultural activities of the Neolithic period at ca. 7000 cal BP. Subsequently, humans rather than climate triggered changes in vegetation composition and structure. We conclude that Fagus sylvatica forests were resilient to long-term anthropogenic and climatic impacts of the Mid and the Late Holocene. However, future climate warming and in particular declining moisture availability may cause unprecedented reorganizations of central European beech-dominated forest ecosystems.
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Ondráčková, Lenka. "Longitudinal development of clast shape characteristics from different material sources in Hrbye River, Central Svalbard." Czech Polar Reports 10, no. 2 (July 1, 2020): 189–202. http://dx.doi.org/10.5817/cpr2020-2-15.
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The sediment transport in polar regions is highly changeable and it is getting faster in connection with a climate change. This study describes the Hrbye River catchment located in the northern Billefjorden, Central Svalbard. The Czech Arctic Station and AMUPS - Adam Mickiewicz University Polish Polar Station are located in near this locality Petunia Bay. The material for this study was sampled in August 2016, during the summer research campaign of Czech Arctic Station together with a cooperation between Masaryk University in Brno and the University of Oslo via Norway Grants. The catchment area is 60 km2. The area of interest lies around the 10 km long Hrbye River in its braidplain, which is 2.3 km wide and 4.5 km long. In the Hrbye Glacier forefield, 27 sediment sampling localities were selected and defined into seven groups: (i) esker complex; (ii) debris stripes; (iii) till plain; (iv) hummocky moraine; (v) post-LIA braidplain; (vi) LIA moraine; (vii) LIA braidplain. Three main petrological types of rocks were studied (SVP – sandstone, VAP – limestone, ORT – orthogneiss). Lithology and roundness of the clasts were evaluated in order to study clast shape properties from various glacial sediments. The results show the dominant role of lithology on the clast shape modification in the Hrbye Glacier forefield.
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Nielsen, J. K., and S. Helama. "Christian Theodor Vaupell, a Danish 19th century naturalist and a pioneering developer of the Quaternary geoscience." History of Geo- and Space Sciences 3, no. 2 (September 5, 2012): 143–50. http://dx.doi.org/10.5194/hgss-3-143-2012.
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Abstract. Christian Theodor Vaupell (1821–1862) was a Danish scholar with pioneering investigations particularly on the late Quaternary development of bog forests, but also microscopy of plant anatomy and vegetative reproduction. His studies contributed to the early scientific thinking of the Quaternary environmental changes. Before his academic efforts, he had already survived the war between Prussia and Denmark albeit he became severely wounded and his left arm was amputated. The drama of his academic efforts, on the other hand, lies in the more or less suspicious dispute of his first doctoral thesis and his dismissal from the academic world during the following years. At the same time, he earned praise for his first thesis (never accepted as thesis but published as a regular book) from abroad; he was also able to attract private foundations for financial support of his scientific work. Following the enthusiasm of his time, Vaupell became attracted to the pine megafossils known to have been preserved in the bogs in north-west Europe. The megafossils led him to study not only the life systems of the ancient and modern bog forests but also their associations with Earth processes. As an interesting detail of his research, Vaupell made compound interpretations on the occurrence of megafossil stumps and their tree-ring growth patterns. In the course of the 20th century, Vaupell's studies have been cited as a general reference of post-glacial vegetation change and plant succession rather than clearly pioneering investigations of palaeoecology, an angle that we would like put into a contrasting perspective. To do so, we provide a brief portrait of Christian Vaupell and his research career. In conclusion, we wish to emphasize the comprehensiveness of Vaupell's views on the late Quaternary vegetation changes and the role of plant succession in that development.
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Pietrafesa, Leonard J., Shaowu Bao, Norden E. Huang, Paul T. Gayes, Tingzhuang Yan, and Michael P. Slattery. "Great Lakes Water Levels: Decomposing Time Series for Attribution." Advances in Data Science and Adaptive Analysis 08, no. 02 (April 2016): 1650009. http://dx.doi.org/10.1142/s2424922x16500091.
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Great Lakes water levels have been trending downwards throughout the 20th and into the 21st centuries. Potential causes are numerous. There have been dredging and water diversion projects over the last 110 years, increasing demand for fresh water consumption from a rising population, and considerable variations in environmental factors (rainfall, snowfall, air temperature, and wind), all causal in nature. A thorough assessment of the National Ocean and Atmospheric Administration (NOAA) National Center for Environmental Information (NCEI) and the NOAA National Centers for Environmental Prediction and the National Center for Atmospheric Research (NCEP/NCAR) — Reanalysis Project (RP) archives of time series of winds, air temperatures, rainfall and snowfall, and water level data, reveals that falling lake levels can be linked to rising air temperatures. Nonuniform, post-glacial, isostatic adjustments of the entire Great Lakes region has further complicated the system as land mass tilting causes localized uplift or subsidence that has also altered relative water levels. A mathematical decomposition of the various data sets and accessory calculations strongly indicate regional atmospheric temperature increases over the entire 20th century and the early 21st century resulting in increased evaporation, appears to be the dominant driving factor in the continued downward trend of water levels in the Great Lakes. Moreover, a high degree of correlation was discovered in comparing water level in the Great Lakes with the comparable temporal variability and record length trends evident both the Global (Land and Ocean) Surface Temperature Anomaly (GSTA) time series and the Atlantic Multidecadal Oscillation (the AMO). It is of note that there have been several water level events since 2013 from which the long term losses of fresh water have undergone a change and the lakes have gained fresh water. This presents an apparent quandary to our nearly 120 year, record length study which revealed downward trends in water levels. To wit, this recent upward movement begs the question: Is the two-year change a precursor to increases in water levels or is it just a local blip? We will focus on data up to 2013, but comment upon recently reported increases as part of our analyses.
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Kuriata-Potasznik, Angela B., and Sławomir Szymczyk. "Variability of the water availability in a river lake system – A case study of Lake Symsar." Journal of Water and Land Development 31, no. 1 (December 1, 2016): 87–96. http://dx.doi.org/10.1515/jwld-2016-0039.
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AbstractIt is predicted that climate change will result in the diminution of water resources available both on global and regional scales. Local climate change is harder to observe and therefore, while counteracting its effects, it seems advisable to undertake studies on pertinent regional and local conditions. In this research, our aim was to assess the impact of a river and its catchment on fluctuations in the water availability in a natural lake which belongs to a post-glacial river and lake system. River and lake systems behave most often like a single interacting hydrological unit, and the intensity of water exchange in these systems is quite high, which may cause temporary water losses. This study showed that water in the analyzed river and lake system was exchanged approx. every 66 days, which resulted from the total (horizontal and vertical) water exchange. Also, the management of a catchment area seems to play a crucial role in the local water availability, as demonstrated by this research, where water retention was favoured by wooded and marshy areas. More intensive water retention was observed in a catchment dominated by forests, pastures and wetlands. Wasteland and large differences in the land elevation in the tested catchment are unfavourable to water retention because they intensify soil evaporation and accelerate the water run-off outside of the catchment. Among the actions which should be undertaken in order to counteract water deficiencies in catchment areas, rational use and management of the land resources in the catchment are most often mentioned.
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OHKOUCHI, Naohiko, and Asahiko TAIRA. "Post-Glacial Marine Environmental Changes Revealed from Deep Sea Sediments." Quaternary Research (Daiyonki-Kenkyu) 30, no. 4 (1991): 297–312. http://dx.doi.org/10.4116/jaqua.30.297.
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Ivanochko, Tara S., Stephen E. Calvert, John R. Southon, Randolph J. Enkin, Judith Baker, Audrey Dallimore, and Thomas F. Pedersen. "Determining the post-glacial evolution of a northeast Pacific coastal fjord using a multiproxy geochemical approachThis article is one of a series of papers published in this Special Issue on the theme Polar Climate Stability Network." Canadian Journal of Earth Sciences 45, no. 11 (November 2008): 1331–44. http://dx.doi.org/10.1139/e08-030.
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A 40.32 m piston core recovered from Effingham Inlet, on the west coast of Vancouver Island, provides the basis for a high-resolution geochemical study of the last deglaciation and the Holocene. Glacial retreat, basin isolation, sea-level rise, and productivity variations are determined using proxies for sediment composition (K/Al, Fe/Al, Mg/Al), grain size (Ti/Al, Zr/Al), sedimentary redox conditions (Mo/Al, U/Al), and productivity (wt.% organic carbon, wt.% opal). As local ice retreated and marine waters inundated the basin, coarse-grained glacimarine sediments were replaced by finer grained, laminated, opal-rich sediments. During meltwater pulse-1a, the dominance of local crustal rise over eustatic sea-level rise resulted in the progressive restriction of ocean circulation in Effingham Inlet and the formation of a temporary freshwater lake. The transition into stable Holocene conditions was initiated at ∼12 700 BP, which corresponds to the onset of the Younger Dryas, as identified by the Greenland Ice core Project (GRIP) ice core δ18O record and was completed by 10 700 BP, ∼800 years after the GRIP ice core record stabilized. Holocene Mo/Al and U/Al ratios range between 12–35 (×104) and 1–3.4 (×104), respectively, indicating that although large-amplitude, high-frequency fluctuations occur, the sediments of Effingham Inlet inner basin have remained organic rich and oxygen depleted for the entire Holocene period. The combination of anoxic bottom waters and a Holocene sedimentation rate of 217 cm/ka have preserved a high-resolution record of environmental change in the northeast Pacific over the last 11 000 years.
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Heinz, C., and M. Barbaza. "Environmental changes during the Late Glacial and Post-Glacial in the central Pyrenees (France): new charcoal analysis and archaeological data." Review of Palaeobotany and Palynology 104, no. 1 (November 1998): 1–17. http://dx.doi.org/10.1016/s0034-6667(98)00050-5.
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Le Hir, G., Y. Goddéris, Y. Donnadieu, and G. Ramstein. "A geochemical modelling study of the evolution of the chemical composition of seawater linked to a "snowball" glaciation." Biogeosciences 5, no. 1 (February 21, 2008): 253–67. http://dx.doi.org/10.5194/bg-5-253-2008.
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Abstract. The Snowball Earth theory initially proposed by Kirschvink (1992) to explain the Neoproterozoic glacial episodes, suggested that the Earth was fully ice-covered at 720 Ma (Sturtian episode) and 640 Ma (Marinoan episode). This succession of extreme climatic crises induced environmental perturbations which are considered as a strong selective pressure on the evolution of life (Hoffman et al., 1998). Using a numerical model of carbon-alkalinity global cycles, we quantify environmental stresses caused by a global glaciation. According to our results, we suggest that during global glaciations, the ocean becomes acidic (pH~6), and undersaturated with respect to carbonate minerals. Moreover the quick transition from ice-house to greenhouse conditions implies an abrupt and large shift of the oceanic surface temperature which causes an extended hypoxia. The intense continental weathering, in the aftermath of the glaciation, deeply affects the seawater composition inducing rapid changes in terms of pH and alkalinity. We also propose a new timing for post glacial perturbations and for the cap carbonates deposition, ~2 Myr instead of 200 kyr as suggested in a previous modelling study. In terms of Precambrian life sustainability, seawater pH modifications appear drastic all along the glaciation, but we suggest that the buffering action of the oceanic crust dissolution avoids a total collapse of biological productivity. But short-lived and large post-glacial perturbations are more critical and may have played the role of an environmental filter proposed in the classic snowball Earth theory. Although the link between environmental changes and life sustainability cannot be modelled accurately, we suggest that only a permissive life (Knoll, 2003) may explain the relative continuity in microfossils diversity observed before, during and after Neoproterozoic glaciation events.
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Liu, Jian, Yoshiki Saito, Xianghuai Kong, Hong Wang, and Ling Zhao. "Geochemical characteristics of sediment as indicators of post-glacial environmental changes off the Shandong Peninsula in the Yellow Sea." Continental Shelf Research 29, no. 7 (April 2009): 846–55. http://dx.doi.org/10.1016/j.csr.2009.01.002.
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LIU, Jian. "Magnetic mineral diagenesis in the post-glacial muddy sediments from the southeastern South Yellow Sea: Response to marine environmental changes." Science in China Series D 48, no. 1 (2005): 112. http://dx.doi.org/10.1360/02yd0353.
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Epp, L. S., G. Gussarova, S. Boessenkool, J. Olsen, J. Haile, A. Schrøder-Nielsen, A. Ludikova, et al. "Lake sediment multi-taxon DNA from North Greenland records early post-glacial appearance of vascular plants and accurately tracks environmental changes." Quaternary Science Reviews 117 (June 2015): 152–63. http://dx.doi.org/10.1016/j.quascirev.2015.03.027.
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LIU, Jian. "Magnetic mineral diagenesis in the post-glacial muddy sediments from the southeastern South Yellow Sea: Re-sponse to marine environmental changes." Science in China Series D 48, no. 1 (2005): 134. http://dx.doi.org/10.1360/02yd0302.
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Sienkiewicz, Elwira. "Post-glacial acidification of two alpine lakes (Sudetes Mts., SW Poland), as inferred from diatom analyses." Acta Palaeobotanica 56, no. 1 (June 1, 2016): 65–77. http://dx.doi.org/10.1515/acpa-2016-0002.
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Abstract Past environmental changes in mountain lakes can be reconstructed with the use of subfossil diatoms from post-glacial sediments. This study applied such an analysis to two mountain lakes in the Sudetes Mts. in Poland: Mały Staw (MS) and Wielki Staw (WS). Cores 882 cm long (MS) and 1100 cm long (WS) taken from the centre of each lake in 1982 were used to study the long-term acidification history of these lakes. Changes in vegetation indicate that the initial phase of MS started at the end of the Pleistocene. WS sediments began to accumulate shortly after that, at the beginning of the Holocene. The majority of the diatom assemblages are typical of oligotrophic acidic lakes located in alpine and arctic regions. A pH reconstruction based on diatoms (DI-pH) showed long-term acidification dating to almost the beginning of the lakes’ existence. Natural acidification began after the deglaciation, and the most intensive acidification continued to the end of the mid-Holocene. Through the whole period studied, pH decreased by 1.4 in MS and 0.9 in WS. After a period of relatively stable lake water pH, it decreased rapidly during the last few decades of the 20th century, due to anthropogenic pollution: pH declined by 0.7 in MS and 0.3 in WS. Mały Staw, being shallower, smaller, and with a larger drainage basin than Wielki Staw, is more sensitive to acid deposition; this accounts for the difference in pH.
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Herman, Jeremy S., and Jeremy B. Searle. "Post-glacial partitioning of mitochondrial genetic variation in the field vole." Proceedings of the Royal Society B: Biological Sciences 278, no. 1724 (April 20, 2011): 3601–7. http://dx.doi.org/10.1098/rspb.2011.0321.
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Genetic markers are often used to examine population history. There is considerable debate about the behaviour of molecular clock rates around the population-species transition. Nevertheless, appropriate calibration is critical to any inference regarding the absolute timing and scale of demographic changes. Here, we use a mitochondrial cytochrome b gene genealogy, based entirely on modern sequences and calibrated from recent geophysical events, to date the post-glacial expansion of the Eurasian field vole ( Microtus agrestis ), a widespread temperate mammal species. The phylogeographic structure reflects the subsequent expansion of populations that went through bottlenecks at the time of the Younger Dryas ( ca 12 000 years BP) rather than the Last Glacial Maximum (LGM, ca 24 000 years BP), which is usually seen as the time when present-day patterns were determined. The nucleotide substitution rate that was estimated here, ca 4 × 10 −7 substitutions/site/year, remains extremely high throughout the relevant time frame. Calibration with similarly high population-based substitution rates, rather than long-term rates derived from species divergence times, will show that post-LGM climatic events generated current phylogeographic structure in many other organisms from temperate latitudes.
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Marriner, Nick, Jean-Philippe Goiran, Bernard Geyer, Valérie Matoïan, Michel al-Maqdissi, Marion Leconte, and Pierre Carbonel. "Ancient harbors and Holocene morphogenesis of the Ras Ibn Hani peninsula (Syria)." Quaternary Research 78, no. 1 (April 18, 2012): 35–49. http://dx.doi.org/10.1016/j.yqres.2012.03.005.
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AbstractRas Ibn Hani peninsula, a wave-dominated tombolo (800 × 1000 m) on the Syrian coast, provides evidence for significant Holocene changes that can be linked to geological inheritance, rising post-glacial sea level, sediment supply and human impacts. Initial development of Ras Ibn Hani's coastal system began ~ 8000 years ago when shallow marine environments formed in a context of rising post-glacial sea level. Following relative sea-level stabilization ~ 6000 cal yr BP, beach facies trace the gradual formation of a wave-dominated sandbank fronted by a ~ 2300 × ~ 500 m palaeo-island whose environmental potentiality was attractive to Bronze Age societies. A particularly rapid phase of tombolo accretion is observed after ~ 3500 cal yr BP characterised by a two- to fourfold increase in sedimentation rates. This is consistent with (i) a pulse in sediment supply probably driven by Bronze Age/Iron Age soil erosion in local catchments, and (ii) positive feedback mechanisms linked to regionally attested neotectonics. Archaeological remains and radiocarbon datings confirm that the subaerial tombolo was probably in place by the Late Bronze Age. These data fit tightly with other eastern Mediterranean tombolo systems suggesting that there is a great deal of predictability to their geology and stratigraphy at the regional scale.