scholarly journals Reconstructing Holocene landscape and environmental changes at Lago Rogaguado, Bolivian Amazon

2020 ◽  
Author(s):  
Alena Giesche ◽  
Umberto Lombardo ◽  
Walter Finsinger ◽  
Heinz Veit
Keyword(s):  
Environmental Changes ◽  
Accumulation Rate ◽  
Sediment Cores ◽  
Tectonic Activity ◽  
Lake Levels ◽  
Fourfold Increase ◽  
Anthropogenic Fire ◽  
Bolivian Amazon ◽  
Geochemical Analyses ◽  
Macroscopic Charcoal

AbstractWe performed geochemical analyses of two lake sediment cores (1.25 and 1.5 m long) from Lago Rogaguado, which is a large (315 km2) and shallow lake in the Llanos de Moxos, Bolivian Amazon, to investigate Holocene environmental changes based on a multi-proxy dataset (XRF, density, grain size, C:N, and macrocharcoal). One of the two cores provides a history of environmental changes in the Llanos de Moxos from 8100 cal BP until present, which supplements previously published pollen and microscopic charcoal records. Our analyses indicate lake expansion at 5800 cal BP, which may relate to tectonic activity. This was followed by further increasing lake levels, peaking at approximately 1050–400 cal BP, which supports increasingly wetter conditions in the Llanos de Moxos after the mid-Holocene. A fourfold increase in macroscopic charcoal accumulation rate and a more than fivefold increase in sedimentation rates supports anthropogenic fire activity at around 1450 cal BP (500 CE), suggesting that pre-Columbian populations used fire to actively manage the landscape during a period of maximum lake levels around Lago Rogaguado. From 400–100 cal BP, higher C:N, larger grain sizes and peaks in macroscopic charcoal accumulation rates suggest increased watershed erosion associated with increased biomass burning, possibly related to intensified land use.

High-resolution radiocarbon dating to reconstruct last century environmental changes in the pacific island of Espiritu Santo

2021 ◽  
Author(s):  
Giorgia Camperio ◽  
Caroline Welte ◽  
S. Nemiah Ladd ◽  
Matthew Prebble ◽  
Nathalie Dubois
Keyword(s):  
High Resolution ◽  
Radiocarbon Dating ◽  
Environmental Changes ◽  
Accumulation Rate ◽  
Sediment Cores ◽  
Volcanic Eruptions ◽  
High Accumulation ◽  
Sedimentary Records ◽  
The Pacific ◽  
Rapid Accumulation

<p>Espiritu Santo is one of the 82 islands of the archipelago of Vanuatu and is the largest, highest, and most biodiverse of the insular country. Climatic changes linked to El Niño and extreme events such as cyclones and volcanic eruptions are a daily challenge in this remote area. These events can be recorded in sedimentary archives. Here we present a multi-proxy investigation of sediment cores retrieved from two small lakes located on the West coast of Espiritu Santo. Although the records span the last millennium, high-resolution radiocarbon dating of macrofossils reveals a rapid accumulation of sediment in the past 100 years. The high accumulation rate coupled with the high-resolution dating of freshwater sediments allows us to compare the <sup>14</sup>C bomb curve with the biogeochemical proxies of the sedimentary records. The results can then be validated against written and oral historical records linked with the societal perception of recent environmental changes in this vulnerable ecosystem.</p><div> <div title="Translate selected text"></div> <div title="Play"></div> <div title="Copy text to Clipboard"></div> </div>

The Paleochrono probabilistic model to derive a consistent chronology for several paleoclimatic sites

2021 ◽  
Author(s):  
Frédéric Parrenin ◽  
Lucie Bazin ◽  
Christo Buizert ◽  
Emilie Capron ◽  
Jai Chowdry Beeman ◽  
...  
Keyword(s):  
Probabilistic Model ◽  
Environmental Changes ◽  
Accumulation Rate ◽  
Ice Core ◽  
Sediment Cores ◽  
Computing Time ◽  
Ice Cores ◽  
Ease Of Use ◽  
Sequence Of Events ◽  
Different Types

<p>Past climatic and environmental changes can be reconstructed thanks to paleoclimatic archives such as ice cores, marine sediment cores, lake sediment cores, speleothems, tree rings, corals, etc. The dating of these natural archives is crucial for deciphering the temporal sequence of events during past climate changes. It is also essential to estimate the absolute and relative errors of such estimated chronologies. This task is, however, complex since it involves the combination of different dating approaches on different paleoclimatic sites and often different types of archives. Here we present Paleochrono, a new probabilistic model to derive a common and probalistically optimal chronology for several paleoclimatic sites with potentially different types of archives. Paleochrono is based on the inversion of an archiving model: a varying deposition rate (also named sedimentation or accumulation rate) and also, for ice cores, a lock-in-depth of air bubbles (since air is not trapped at surface) and a thinning function (since ice undergoes flow). The model integrates several types of chronological information: prior knowledge of the archiving process, independently dated horizons, depth intervals of known duration, undated stratigraphic links between records, and, for ice cores, Δdepth observations (depth differences between synchronous events recorded in the bubbles and ice, respectively). The optimization is formulated as a least-squares problem, assuming that all densities of probabilities are near-Gaussian and that the model is almost linear in the vicinity of the best solution. Paleochrono is the successor of IceChrono, which was dealing only with ice-core records. Paleochrono performs better than IceChrono in terms of computational efficiency, ease of use, and accuracy. We demonstrate the ability of Paleochrono in a new AICC2012-Hulu dating experiment, which combines the AICC2012 dating experiment, based on records from five polar ice cores, with data from two U/Th-dated speleothems from Hulu Cave (China). We analyse the performance of Paleochrono in terms of computing time and memory usage in various dating experiments. Paleochrono is freely available under the MIT open source license.</p>

Geomorphology of the lakebed and sediment deposition during the Holocene in Lake Visovac

2021 ◽  
Author(s):  
Nikolina Ilijanić ◽  
Slobodan Miko ◽  
Ozren Hasan ◽  
Dea Brunović ◽  
Martina Šparica Miko ◽  
...  
Keyword(s):  
High Resolution ◽  
Lake Sediment ◽  
National Park ◽  
Lake Level ◽  
Evolutionary Dynamics ◽  
Environmental Changes ◽  
Sediment Cores ◽  
Depositional Environments ◽  
Lake Levels ◽  
The Holocene

<p>Lake Visovac is a tufa barrier lake on the Krka River between Roški slap (60 m asl) and Skradinski buk (46 m absl) waterfalls, included in the Krka national park as primarily unaltered area of exceptional natural value. Paleolimnological research was conceived to address a lake evolution and depositional environments through the geophysical survey and collection of the lake sediment cores. A high-resolution bathymetric map was obtained using a multibeam sonar. The average lake depth varies between 20 and 25 m. Sediment cores were investigated to extract physical properties, sedimentological, mineralogical, geochemical and paleoecological records constrained by the radiocarbon chronology, to understand what was happening to both the landscapes and lakescapes of Lake Visovac during the last 2.000 cal yr.</p><p>Significant findings of the project are geomorphological features on the lake bottom: submerged sinkholes of various sizes (up to 40 m deep); submerged tufa barriers in the area of Kalički kuk (southern part of Lake Visovac) at the depths of 15 and 17 m, followed by a series of buried cascade tufa barriers at the depth of 25 m covered with up to 10 m of Holocene lake sediments; submerged vertical tufa barrier up to 32 m-high near the mouth of Čikola River; submerged landslides, small (river) fan structures characterized by sediment waves. Ground-penetrating-radar (GPR) data have been acquired due to the presence of gas-saturated sediments over a large area of the lake, that limited the use of high-resolution acoustic profiling. A total thickness of sediments is up to 40 m. High resolution paleoenvironmental record through the Late Holocene gives evidence of high sedimentation rates in Lake Visovac, variable soil erosion impact on lake sediment composition and carbonate authigenic sedimentation. Higher organic carbon is observed in the last 50 years due to changes in land cover and reforestation. Pleistocene lake sediment outcrops occur up to 20 m above the present lake levels indicating higher lake levels as a consequence of higher elevation of tuffa barriers. Kalički kuk, which lies up to 20 m above present lake level, is a remnant of these barriers which have been dated to MIS5. Results allow us to interpret the environmental and evolutionary dynamics of Lake Visovac in the following way: lake level more than 20 m higher than today in mid-Pleistocene with significantly larger lake volume in Lake Visovac, with active Kalički kuk and Skradinski buk waterfalls; lower lake-level at the beginning of the Holocene when several small lakes existed in isolated basins in the area of Lake Visovac. The tufa barrier at Skradinski buk started to grow faster than the Kalički kuk barriers and waterfalls resulting in their flooding and submergence during the Holocene. The tufa barrier at Skradinski buk has grown 15 m since then. This study demonstrates the role of geomorphological lakebed characteristics in reshaping our understanding of the environmental changes and the future of Lake Visovac.</p><p>The research was conducted as part of the project funded by the Krka National Park and CSF funded QMAD project (IP-04-2019-8505).</p>

A 350014C yr High-Resolution Record of Water-Level Changes in Lake Titicaca, Bolivia/Peru

1997 ◽  
Vol 47 (2) ◽  
pp. 169-180 ◽  
Author(s):  
Mark B. Abbott ◽  
Michael W. Binford ◽  
Mark Brenner ◽  
Kerry R. Kelts
Keyword(s):  
Water Level ◽  
Lake Level ◽  
Sediment Cores ◽  
Water Level Fluctuations ◽  
Lake Levels ◽  
Cultural Changes ◽  
Lake Titicaca ◽  
Water Level Rise ◽  
Andean Altiplano ◽  
Geochemical Analyses

Sediment cores collected from the southern basin of Lake Titicaca (Bolivia/Peru) on a transect from 4.6 m above overflow level to 15.1 m below overflow level are used to identify a new century-scale chronology of Holocene lake-level variations. The results indicate that lithologic and geochemical analyses on a transect of cores can be used to identify and date century-scale lake-level changes. Detailed sedimentary analyses of subfacies and radiocarbon dating were conducted on four representative cores. A chronology based on 60 accelerator mass spectrometer radiocarbon measurements constrains the timing of water-level fluctuations. Two methods were used to estimate the14C reservoir age. Both indicate that it has remained nearly constant at ∼25014C yr during the late Holocene. Core studies based on lithology and geochemistry establish the timing and magnitude of five periods of low lake level, implying negative moisture balance for the northern Andean altiplano over the last 3500 cal yr. Between 3500 and 3350 cal yr B.P., a transition from massive, inorganic-clay facies to laminated organic-matter-rich silts in each of the four cores signals a water-level rise after a prolonged mid-Holocene dry phase. Evidence of other significant low lake levels occurs 2900–2800, 2400–2200, 2000–1700, and 900–500 cal yr B.P. Several of the low lake levels coincided with cultural changes in the region, including the collapse of the Tiwanaku civilization.

An Assessment of Environmental Changes in Three Lakes from King's County (Nova Scotia, Canada) Using Diatom-Based Paleolimnological Techniques

2008 ◽  
Vol 43 (2-3) ◽  
pp. 85-98 ◽  
Author(s):  
Joshua R. Thienpont ◽  
Brian K. Ginn ◽  
Brian F. Cumming ◽  
John P. Smol
Keyword(s):  
Nova Scotia ◽  
Environmental Changes ◽  
Sediment Cores ◽  
Lake Management ◽  
River System ◽  
210Pb Dating ◽  
Hydroelectric Power ◽  
Diatom Assemblages ◽  
Shoreline Development ◽  
Before And After

Abstract Paleolimnological approaches using sedimentary diatom assemblages were used to assess water quality changes over the last approximately 200 years in three lakes from King's County, Nova Scotia. In particular, the role of recent shoreline development in accelerating eutrophication in these systems was assessed. Sediment cores collected from each lake were analyzed for their diatom assemblages at approximately 5-year intervals, as determined by 210Pb dating. Analyses showed that each system has changed, but tracked different ecosystem changes. Tupper and George lakes recorded shifts, which are likely primarily related to climatic warming, with diatom assemblages changing from a preindustrial dominance by Aulacoseira spp. to present-day dominance by Cyclotella stelligera. In addition to the recent climatic-related changes, further diatom changes in the Tupper Lake core between approximately 1820 and 1970 were coincident with watershed disturbances (farming, forestry, and construction of hydroelectric power infrastructure). Black River Lake has recorded an increase in diatom-inferred total phosphorus since about 1950, likely due to impoundment of the Black River system for hydroelectric generation and subsequent changes in land runoff. Before-and-after (i.e., top-bottom) sediment analyses of six other lakes from King's County provided further evidence that the region is being influenced by climatic change (decreases in Aulacoseira spp., increases in planktonic diatom taxa), as well as showing other environmental stressors (e.g., acidification). However, we recorded no marked increase in diatom-inferred nutrient levels coincident with shoreline cottage development in any of the nine study lakes. Paleolimnological studies such as these allow lake managers to place the current limnological conditions into a long-term context, and thereby provide important background data for effective lake management.

Pigment Preservation in Lake Sediments: A Comparison of Sedimentary Environments in Trout Lake, Wisconsin

1991 ◽  
Vol 48 (3) ◽  
pp. 472-486 ◽  
Author(s):  
James P. Hurley ◽  
David E. Armstrong
Keyword(s):  
Accumulation Rate ◽  
Sediment Cores ◽  
Sediment Accumulation ◽  
Sediment Surface ◽  
Water Interface ◽  
Sedimentary Pigments ◽  
Sedimentary Environments ◽  
Trout Lake ◽  
Secondary Carotenoids ◽  
Β Carotene

Fluxes and concentrations of a phorbins and major algal carotenoids were quantified in sediment trap material and sediment cores from two basins of Trout Lake, Wisconsin (TrDH and TrAB). The basins were chosen to contrast the influence of oxygen content at the sediment–water interface (TrDH, oxic and TrAB, reducing), sediment accumulation rate, and focusing. Pigment diagenesis occurred in both basins, but transformations and destruction were more extensive in TrDH. Although untransformed chlorophyll a was the major phorbin deposited at the sediment surface of both basins (51–64 mol%), pigment destruction, coupled with transition to pheophytin, accounted for substantial losses, especially in oxic TrDH sediments. Fucoxanthin, peridinin, and diadinoxanthin, despite representing > 70% of the deposited carotenoid flux, were substantially degraded or transformed in both basins. However, preservation was relatively high for secondary carotenoids, such as diatoxanthin and β-carotene, and for a major cryptomonad pigment, alloxanthin. Residual profiles in sediments show that pigment sedimentation from the epilimnion and accumulation in the permanent sediments are not directly related and that diagenesis must be considered in interpreting sedimentary pigments.

scholarly journals Late Quaternary paleoenvironment of the Ross Sea continental shelf, Antarctica

1998 ◽  
Vol 27 ◽  
pp. 275-280 ◽  
Author(s):  
Akira Nishimura ◽  
Toru Nakasone ◽  
Chikara Hiramatsu ◽  
Manabu Tanahashi
Keyword(s):  
Organic Carbon ◽  
Marine Environment ◽  
Environmental Changes ◽  
Ross Sea ◽  
Late Quaternary ◽  
Sedimentary Environment ◽  
Sediment Cores ◽  
Ice Sheet ◽  
Ice Shelf ◽  
Accelerator Mass Spectrometer

Based on sedimenlological and micropaleontological work on three sediment cores collected at about 167° Ε in the western Ross Sea, Antarctica, and accelerator mass spectrometer l4C ages of organic carbon, we have reconstructed environmental changes in the area during the late Quaternary. Since 38 ka BP at latest, this area was a marine environment with low productivity. A grounded ice sheet advanced and loaded the sediments before about 30-25 ka BP. After 25 ka BP, the southernmost site (76°46'S) was covered by floating ice (shelf ice), preventing deposition of coarse terrigenous materials and maintaining a supply of diatom tests and organic carbon until 20 ka BP. The northernmost site (74°33'S) was in a marine environment with a moderate productivity influenced by shelf ice/ice sheet after about 20 ka BP. Since about 10 ka BP, a sedimentary environment similar to the present-day one has prevailed over this area.

Climate Variation and the Rise and Fall of an Andean Civilization

1997 ◽  
Vol 47 (2) ◽  
pp. 235-248 ◽  
Author(s):  
Michael W. Binford ◽  
Alan L. Kolata ◽  
Mark Brenner ◽  
John W. Janusek ◽  
Matthew T. Seddon ◽  
...  
Keyword(s):  
Agricultural Production ◽  
Climate Changes ◽  
Drainage Basin ◽  
Sediment Cores ◽  
Agricultural Field ◽  
Lake Levels ◽  
Level Variation ◽  
Spatial And Temporal Patterns ◽  
Lake Titicaca ◽  
Basin Water

Paleolimnological and archaeological records that span 3500 years from Lake Titicaca and the surrounding Bolivian–Peruvian altiplano demonstrate that the emergence of agriculture (ca. 1500 B.C.) and the collapse of the Tiwanaku civilization (ca. A.D. 1100) coincided with periods of abrupt, profound climate change. The timing and magnitude of climate changes are inferred from stratigraphic evidence of lake-level variation recorded in14C-dated lake-sediment cores. Paleo-lake levels provide estimates of drainage basin water balance. Archaeological evidence establishes spatial and temporal patterns of agricultural field use and abandonment. Prior to 1500 B.C., aridity in the altiplano precluded intensive agriculture. During a wetter period from 1500 B.C. to A.D. 1100, the Tiwanaku civilization and its immediate predecessors developed specialized agricultural methods that stimulated population growth and sustained large human settlements. A prolonged drier period (ca. A.D. 1100–1400) caused declining agricultural production, field abandonment, and cultural collapse.

scholarly journals Age and paleoenvironment of the Nukhul Formation, Gulf of Suez, Egypt: Insights from palynology, palynofacies and organic geochemistry

GeoArabia ◽  
2013 ◽  
Vol 18 (4) ◽  
pp. 137-174
Author(s):  
Haytham El Atfy ◽  
Rainer Brocke ◽  
Dieter Uhl
Keyword(s):  
Nile Delta ◽  
Organic Geochemistry ◽  
Regional Scale ◽  
Tectonic Activity ◽  
Gulf Of Suez ◽  
Spores And Pollen ◽  
Shallow Marine ◽  
History Of ◽  
Geochemical Analyses ◽  
Rock Eval

ABSTRACT Palynological results of a detailed study carried out on 56 samples retrieved from two selected wells (GH 404-2A and SA-E6A) of the Hilal and Shoab Ali fields within the southern part of the Gulf of Suez, Egypt, are presented. This study is mainly focused on the poorly dated Nukhul Formation, for which very little information from palynology is available despite its importance from a petroleum viewpoint. The assemblages discovered in our study are moderately preserved and reveal a sparse but significant record of spores and pollen and dinoflagellates together with highly diverse fungi and algal taxa, e.g. Botryococcus and Pediastrum. A latest Oligocene–Early Miocene (Chattian–Aquitanian) age has been suggested for the Nukhul Formation, based on compiling palynostratigraphic and ecologic data obtained from palynomorphs that have previously been assumed to be representatives for this period on a regional scale. In addition, the Oligocene/Miocene Boundary (OMB) could be lithostratigraphically defined within the studied formation, most likely at the boundary between the lower Shoab Ali Member and upper Ghara Member. A fungal/algal ‘event’ within the interval from 11,370–11,430 ft in the GH 404-2A Well may be associated with a strong regressive phase. Such a regression was previously observed in the Nile Delta and other locations around the Red Sea province, and may be assigned to the global Mi-1 glaciation event at the OMB. However, not only glacial-driven eustacy but also tectonic activity related to the Gulf of Suez rifting may have contributed in forming such an event. Palynofacies investigations were carried out under both transmitted and fluorescence microscopy and the results were partly supplemented by existing organic geochemical analyses (GH 404-2A Well) involving Rock-Eval pyrolysis and total organic carbon (TOC) measurements. The analysis was used to interpret the depositional regime, paleoenvironment and thermal maturation history of the studied succession. These results support the temporary existence of shallow, pond- or lake-like aquatic habitats during deposition of the lower Shoab Ali Member that evolved into a shallow-marine environment with the onset of the deposition of upper Ghara Member of the Nukhul Formation.

scholarly journals Análisis comparativo de los moluscos en la reserva de la biosfera Los Petenes y lagunas costeras del sureste de México

2018 ◽  
Vol 47 (1) ◽  
Author(s):  
Alicia González-Solis ◽  
Daniel Torruco ◽  
Ángel D. Torruco-González
Keyword(s):  
Comparative Evaluation ◽  
Environmental Changes ◽  
Sediment Cores ◽  
Biosphere Reserve ◽  
Study Data ◽  
The Other ◽  
Water Bodies ◽  
Terminos Lagoon ◽  
Multiple Uses ◽  
Trophic Chains

The phylum Mollusca is widely distributed in all types of environments. The species it contains are important for their multiple uses as food (as part of several trophic chains), as vectors of other groups of organisms, for the extraction of substances, and as sentinels ofnatural and induced environmental changes. In this work, a comparative evaluation of the malacological biodiversity associated with different habitats in the Los Petenes Biosphere Reserve in Campeche and in eight coastal water bodies in southeastern Mexico was performed.To obtain data comparable to those that were used in a previous study, data from the Los Petenes mollusks were obtained by collection of sediment cores 10 cm in diameter at a depth of 15 cm at 20 sites in different habitats every four months during 2014. For the other lagoons,records were obtained from various published sources. For Los Petenes, a total of 175 species and 12,850 individuals were recorded. The species Rissoella caribaea was the most common and the most abundant. Comparative evaluation of each of the habitats that coexist in this ecosystem did not show significant changes in abundance. Similarly, faunal associations exhibited a sea-land gradient, and although thedifferences in biomass were significant, species richness did not show the same pattern among habitats. The Los Petenes system as a whole exhibited some of the greatest biodiversity among the water bodies analyzed, and the Terminos lagoon showed the highest biodiversity (169and 175 species, respectively). In contrast, the Sabancuy estuary featured fauna records with a richness of 43 species; in the Tupilco-Ostión lagoon, only 62 species were recorded, and in the rest of the lagoons, the numbers of species were even lower.

Sign in / Sign up

Export Citation Format

Share Document