scholarly journals Late Glacial to Holocene dune development at southern Krakower See

2019 ◽  
Vol 2 ◽  
pp. 83-88 ◽  
Author(s):  
Sebastian Lorenz ◽  
Henrik Rother ◽  
Michael Kenzler ◽  
Sara Kaphengst

Abstract. The site at the southern shore of Krakower See shows the Quaternary geology of the surrounding area. The local Quaternary sequence comprises a thickness of 50–100 m of Quaternary deposits while the surface morphology is dominated by the ice marginal position of the Pomeranian moraine, which passes through the area. The bathymetry of the lake basin of Krakower See indicates a predominant genesis by glaciofluvial erosion in combination with glacial exaration. Past research in this area has focussed on the reconstruction of Pleniglacial to Holocene environmental changes, including lake-level fluctuations, aeolian dynamics, and pedological processes and their modification by anthropogenic land use.

2021 ◽  
Author(s):  
Giulia Wienhues ◽  
Yunuén Temoltzin-Loranca ◽  
Hendrik Vogel ◽  
Martin Grosjean

<p>Lake Victoria (LV), Africa’s largest lake is situated in the African Great Rift Valley. Due to its shallowness (max.68 m; mean 40 m) and limited river inflow, LV is very sensitive to variations in climate and lake level fluctuations. As a result, LV has undergone repeated low stand periods, or even complete desiccation during the Late Pleistocene with profound effects on the aquatic ecosystem. One example is the emergence of a unique biodiversity of endemic cichlid species following the lake’s last desiccation event during the last glacial and subsequent refilling commencing ~15,000 years ago.</p><p>In an interdisciplinary project we aim at reconstructing linkages between paleoenvironmental variability, disturbances and adaptive species radiation by combining approaches from paleogenomics, paleoecology and paleolimnology. For this purpose, four sediment cores along a depth-transect (near-shore to offshore), covering ca. the past 14,000 years, are analyzed.</p><p>We present first paleolimnological results of long-term changes of using (isotope-)geochemical indicators including: Sedimentary pigments and biogenic silica to infer aquatic productivity supported by micro X-ray Fluorescence (XRF) derived element geochemistry, <sup>13</sup>C and <sup>15</sup>N, and sedimentary phosphorus fraction analyses providing information on changes in sediment composition.</p><p>The results suggest that the infilling of the LV basin was a long-term step-wise process. This is shown by elevated and variable indicators for lithogenic input (e.g Ti, Zr and K) and interpreted as mobilization of substrate from the shorelines by a dynamic lake level prior to its stabilization in the Early and Mid-Holocene.  This process is mainly reflected in the core taken at the greatest water depth (65 m). Simultaneously, the aquatic productivity (BSi and chloropigments) increased rapidly after the refilling of the lake basin in the Late-Glacial. A gradual drying of the climate and a following shift to a more oxygenated water column is observed in the Mid-to Late Holocene indicated by a decline in chemically weathered material (e.g Rb/K & K/Al ratios) and abundance of Mn.</p>


2021 ◽  
Author(s):  
Sebastian Schaller ◽  
Michael E. Boettcher ◽  
Marius W. Buechi ◽  
Laura S. Epp ◽  
Stefano C. Fabbri ◽  
...  

<p>The modern basin of trinational Lake Constance, between Switzerland, Germany, and Austria, represents the underfilled northern part of a glacially overdeepened trough. It is over 400 m deep and reaches well into the Alps at its southern end. The overdeepening was formed by the numerous glacial advance-retreat cycles of the Rhine Glacier throughout the Middle to Late Quaternary. A seismic survey of Lake Constance revealed a Quaternary sediment fill of over 150 m thickness under the modern lake floor in a maximal water depth of >250 m. This sedimentary sequence represents at least the last glacial cycle with ice-contact deposits at the base on top of the Molasse bedrock overlain by glaciolacustrine to lacustrine sediments. During the successful field test of a newly developed mid-size coring system ("HIPERCORIG"), the longest core ever taken in Lake Constance was recovered with an overall length of 24 m. The drill core, taken in a water depth of 200 m, consists of a nearly continuous succession of lacustrine sediments including over 12 m of pre-Holocene sediment at the base. The entire core was petrophysically and geochemically analyzed, sedimentologically described, and 14 lithotypes were identified. In combination with a <sup>14</sup>C- and OSL-based age-depth model, the core was divided into three main chronostratigraphic units. The basal age of ~13.7 ka BP places the base of the section back into the Bølling-Allerød interstadial whereas the overlying strata represent a complete Younger-Dryas and Holocene section.</p><p>The sediments offer a high-resolution insight into the evolution of Paleolake Constance from a cold postglacial to a more productive warm Holocene lake. The Late Glacial sections are dominated by massive, m-thick sand beds reflecting episodic sedimentation pulses. They are most likely linked with a subaquatic channel system that is still apparent in today's lake bathymetry despite the Holocene drape. This channel system was fed from a Late Glacial river from the north; provenance analysis of the initially unexpected sands together with hydrologic considerations will document whether this inflowing high-discharge river represented a local catchment (i.e. northern lake shore) or an Alpine signal (i.e. from the south) provided by the Rhine glacier. Tentative pore water hydrogeochemical and isotope analyses indicate a still active flow system at depth. The overlying Holocene section reveals a prominent, several cm-thick double-turbiditic event layer representing the most distal impact of the "Flimser Bergsturz", the largest known rock slide of the Alps that occurred over 100 km upstream the Rhine River at ~9.5 ka BP. Furthermore, lithologic variations in the Holocene section document the varying sediment load of the Rhine and of the endogenic production representing a multitude of environmental changes.</p>


The geology and palaeobotany of Quaternary deposits at Hoxne, Suffolk, have been investigated. It is shown that immediately after the ice which laid down the Lowestoft Till had retreated a lake basin was formed in the till. In the basin a series of interglacial lacustrine sediments was deposited, first clay-mud and later detritus mud. Reworking of these sediments under a periglacial climate with a fluctuating lake water level resulted in the deposition of alternating layers of silt, drift mud and brecciated clay-mud. After this, clay, sand and gravel were deposited in the lake by solifluxion under periglacial conditions. The lake basin as a topographical feature was then entirely obliterated, and clay, sand and till were deposited unconformably on the lake sediments. This till was formed during the Gipping Glaciation. After the retreat of the ice of this glaciation, the present valleys were excavated, and later to a small extent filled by fluvial deposits. Finally, aeolian sand, which now forms the surface deposit in the area, was deposited under periglacial conditions and, probably at the same time, a cryoturbation phase occurred. Macroscopic plant remains and pollen diagrams from the lacustrine interglacial sediments are described. They give evidence of the vegetational and climatic history of the interglacial period between the Lowestoft and Gipping Glaciations. Four major vegetational stages are distinguished; they are named the Late-Glacial, Early-Temperate, Late-Temperate and Early-Glacial stages. The Late-Glacial stage was characterized by Hippophaë scrub, the Early-Temperate stage by the development and persistence of mixed-oak forest, the Late-Temperate stage by the beginning of the replacement of the mixed-oak forest species by Carpinus and conifers, including Picea and Abies , and the Early-Glacial stage by the presence of park-tundra with scattered forest. There was a rapid climatic amelioration at the very beginning of the interglacial period, which led to a climatic optimum in the middle of the Early-Temperate stage. After that time there was a progressive deterioration of the climate, which resulted in the periglacial conditions under which the uppermost sediments of the lake were laid down. A phase of deforestation in the Early-Temperate stage and its relation to the Lower Palaeolithic (Acheulian) artifacts found during the investigations are described; they may be associated. The stratigraphical positions of those artifacts found recently and of those found by previous investigators at Hoxne are also described. The molluscan and mammalian faunas of the deposits and the glacial erratics from the covering till are described in Appendices. The stratigraphy demonstrated here differs from that previously found at Hoxne in showing that there is one interglacial temperate horizon, undivided by a cold phase, whereas previously two temperate horizons separated by a cold phase had been described. The origin of this difference is explained. A comparison of these Quaternary deposits is made with those elsewhere in Britain, in Ireland and on the continent. It is concluded that the Hoxne Interglacial is of Great (Elster/Saale, Mindel/Riss) Interglacial age.


PLoS ONE ◽  
2021 ◽  
Vol 16 (10) ◽  
pp. e0254793
Author(s):  
E. Argiriadis ◽  
M. Bortolini ◽  
N. M. Kehrwald ◽  
M. Roman ◽  
C. Turetta ◽  
...  

Rano Raraku, the crater lake constrained by basaltic tuff that served as the primary quarry used to construct the moai statues on Rapa Nui (Easter Island), has experienced fluctuations in lake level over the past centuries. As one of the only freshwater sources on the island, understanding the present and past geochemical characteristics of the lake water is critical to understand if the lake could have been a viable freshwater source for Rapa Nui. At the time of sampling in September 2017, the maximum lake depth was ~1 m. The lake level has substantially declined in the subsequent years, with the lake drying almost completely in January 2018. The lake is currently characterized by highly anoxic conditions, with a predominance of ammonium ions on nitrates, a high concentration of organic carbon in the water-sediment interface and reducing conditions of the lake, as evidenced by Mn/Fe and Cr/V ratios. Our estimates of past salinity inferred from the chloride mass balance indicates that it was unlikely that Rano Raraku provided a viable freshwater source for early Rapa Nui people. The installation of an outlet pipe around 1950 that was active until the late 1970s, as well as grazing of horses on the lake margins appear to have significantly impacted the geochemical conditions of Rano Raraku sediments and lake water in recent decades. Such impacts are distinct from natural environmental changes and highlight the need to consider the sensitivity of the lake geochemistry to human activities.


2020 ◽  
Vol 12 (3) ◽  
pp. 528 ◽  
Author(s):  
Jingye Li ◽  
Jian Gong ◽  
Jean-Michel Guldmann ◽  
Shicheng Li ◽  
Jie Zhu

Land use/cover change (LUCC) has an important impact on the terrestrial carbon cycle. The spatial distribution of regional carbon reserves can provide the scientific basis for the management of ecosystem carbon storage and the formulation of ecological and environmental policies. This paper proposes a method combining the CA-based FLUS model and the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model to assess the temporal and spatial changes in ecosystem carbon storage due to land-use changes over 1990–2015 in the Qinghai Lake Basin (QLB). Furthermore, future ecosystem carbon storage is simulated and evaluated over 2020–2030 under three scenarios of natural growth (NG), cropland protection (CP), and ecological protection (EP). The long-term spatial variations in carbon storage in the QLB are discussed. The results show that: (1) Carbon storage in the QLB decreased at first (1990–2000) and increased later (2000–2010), with total carbon storage increasing by 1.60 Tg C (Teragram: a unit of mass equal to 1012 g). From 2010 to 2015, carbon storage displayed a downward trend, with a sharp decrease in wetlands and croplands as the main cause; (2) Under the NG scenario, carbon reserves decrease by 0.69 Tg C over 2020–2030. These reserves increase significantly by 6.77 Tg C and 7.54 Tg C under the CP and EP scenarios, respectively, thus promoting the benign development of the regional ecological environment. This study improves our understanding on the impact of land-use change on carbon storage for the QLB in the northeastern Qinghai–Tibetan Plateau (QTP).


Oecologia ◽  
2021 ◽  
Author(s):  
Jörg Bendix ◽  
Nicolay Aguire ◽  
Erwin Beck ◽  
Achim Bräuning ◽  
Roland Brandl ◽  
...  

AbstractTropical mountain ecosystems are threatened by climate and land-use changes. Their diversity and complexity make projections how they respond to environmental changes challenging. A suitable way are trait-based approaches, by distinguishing between response traits that determine the resistance of species to environmental changes and effect traits that are relevant for species' interactions, biotic processes, and ecosystem functions. The combination of those approaches with land surface models (LSM) linking the functional community composition to ecosystem functions provides new ways to project the response of ecosystems to environmental changes. With the interdisciplinary project RESPECT, we propose a research framework that uses a trait-based response-effect-framework (REF) to quantify relationships between abiotic conditions, the diversity of functional traits in communities, and associated biotic processes, informing a biodiversity-LSM. We apply the framework to a megadiverse tropical mountain forest. We use a plot design along an elevation and a land-use gradient to collect data on abiotic drivers, functional traits, and biotic processes. We integrate these data to build the biodiversity-LSM and illustrate how to test the model. REF results show that aboveground biomass production is not directly related to changing climatic conditions, but indirectly through associated changes in functional traits. Herbivory is directly related to changing abiotic conditions. The biodiversity-LSM informed by local functional trait and soil data improved the simulation of biomass production substantially. We conclude that local data, also derived from previous projects (platform Ecuador), are key elements of the research framework. We specify essential datasets to apply this framework to other mountain ecosystems.


2021 ◽  
Vol 10 (7) ◽  
pp. 466
Author(s):  
Wenbo Mo ◽  
Yunlin Zhao ◽  
Nan Yang ◽  
Zhenggang Xu ◽  
Weiping Zhao ◽  
...  

Spatial and quantitative assessments of water yield services in watershed ecosystems are necessary for water resource management and improved water ecological protection. In this study, we used the InVEST model to estimate regional water yield in the Dongjiang Lake Basin in China. Moreover, we designed six scenarios to explore the impacts of climate and land use/land cover (LULC) changes on regional water yield and quantitatively determined the dominant mechanisms of water yield services. The results are expected to provide an important theoretical reference for future spatial planning and improvements of ecological service functions at the water source site. We found that (1) under the time series analysis, the water yield changes of the Dongjiang Lake Basin showed an initial decrease followed by an increase. Spatially, water yield also decreased from the lake area to the surrounding region. (2) Climate change exerted a more significant impact on water yield changes, contributing more than 98.26% to the water yield variability in the basin. In contrast, LULC had a much smaller influence, contributing only 1.74 %. (3) The spatial distribution pattern of water yield services in the watershed was more vulnerable to LULC changes. In particular, the expansion of built-up land is expected to increase the depth of regional water yield and alter its distribution, but it also increases the risk of waterlogging. Therefore, future development in the basin must consider the protection of ecological spaces and maintain the stability of the regional water yield function.


1993 ◽  
Vol 40 (3) ◽  
pp. 332-342 ◽  
Author(s):  
Maria Socorro Lozano-Garcı́a ◽  
Beatriz Ortega-Guerrero ◽  
Margarita Caballero-Miranda ◽  
Jaime Urrutia-Fucugauchi

AbstractIn order to establish paleoenvironmental conditions during the late Quaternary, four cores from the Basin of Mexico (central Mexico) were drilled in Chalco Lake, located in the southeastern part of the basin. The upper 8 m of two parallel cores were studied, using paleomagnetic, loss-on-ignition, pollen, and diatom analyses. Based on 11 14C ages, the analyzed record spans the last 19,000 14C yr B.P. Volcanic activity has affected microfossil abundances, both directly and indirectly, resulting in absence or reduction of pollen and diatom assemblages. Important volcanic activity took place between 19,000 and 15,000 yr B.P. when the lake was a shallow alkaline marsh and an increase of grassland pollen suggests a dry, cold climate. During this interval, abrupt environmental changes with increasing moisture occurred. From 15,000 until 12,500 yr B.P. the lake level increased and the pollen indicates wetter conditions. The highest lake level is registered from 12,500 to ca. 9000 yr B.P. The end of the Pleistocene is characterized by an increase in humidity. From 9000 until ca. 3000 yr B.P. Chalco Lake was a saline marsh and the pollen record indicates warmer conditions. After 3000 yr B.P. the lake level increased and human disturbance dominates the lacustrine record.


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