scholarly journals Improving age-depth correlations by using the LANDO model ensemble

2021 ◽  
Author(s):  
Gregor Pfalz ◽  
Bernhard Diekmann ◽  
Johann-Christoph Freytag ◽  
Liudmila Sryrkh ◽  
Dmitry A. Subetto ◽  
...  
Keyword(s):  
Sediment Core ◽  
Model Comparison ◽  
Sediment Cores ◽  
Age Determination ◽  
Regime Changes ◽  
Modeling Process ◽  
First Case ◽  
Modeling Systems ◽  
Radiocarbon Data ◽  
Lake Systems

Abstract. Age-depth correlations are the key elements in paleoenvironmental studies to place proxy measurements into a temporal context. However, potential influencing factors of the available radiocarbon data and the associated modeling process can cause serious divergences of age-depth correlations from true chronologies, which is particularly challenging for paleolimnological studies in Arctic regions. This paper provides geoscientists with a tool-assisted approach to compare outputs from age-depth modeling systems and to strengthen the robustness of age-depth correlations. We primarily focused in the development on age determination data from a data collection of high latitude lake systems (50° N to 90° N, 62 sediment cores, and a total of 661 dating points). Our approach used five age-depth modeling systems (Bacon, Bchron, clam, hamstr, Undatable) that we linked through a multi-language Jupyter Notebook called LANDO (“Linked age and depth modeling”). Within LANDO we have implemented a pipeline from data integration to model comparison to allow users to investigate the outputs of the modeling systems. In this paper, we focused on highlighting three different case studies: comparing multiple modeling systems for one sediment core with a continuous, undisturbed succession of dating points (CS1 - “Undisturbed sequence”), for one sediment core with scattered dating points (CS2 - “Inconsistent sequence”), and for multiple sediment cores (CS3 - “Multiple cores”). For the first case study (CS1), we showed how we facilitate the output data from all modeling systems to create an ensemble age-depth model. In the special case of scattered dating points (CS2), we introduced an adapted method that uses independent proxy data to assess the performance of each modeling system in representing lithological changes. Based on this evaluation, we reproduced the characteristics of an existing age-depth model (Lake Ilirney, EN18208) without removing age determination data. For the multiple sediment core (CS3) we found that when considering the Pleistocene-Holocene transition, the main regime changes in sedimentation rates do not occur synchronously for all lakes. We linked this behavior to the uncertainty within the modeling process as well as the local variability of the sediment cores within the collection.

Penguin occupation in the Vestfold Hills

2008 ◽  
Vol 21 (2) ◽  
pp. 131-134 ◽  
Author(s):  
Tao Huang ◽  
Liguang Sun ◽  
Yuhong Wang ◽  
Renbin Zhu
Keyword(s):  
Sediment Core ◽  
Environmental Changes ◽  
Sediment Cores ◽  
East Antarctica ◽  
Before Present ◽  
The Holocene ◽  
History Of ◽  
Vestfold Hills ◽  
Free Area ◽  
Ornithogenic Sediment

AbstractDuring CHINARE-22 (December 2005–March 2006), we investigated six penguin colonies in the Vestfold Hills, East Antarctica, and collected several penguin ornithogenic sediment cores, samples of fresh guano and modern penguin bone and feather. We selected seven penguin bones and feathers and six sediments from the longest sediment core and performed AMS14C dating. The results indicate that penguins occupied the Vestfold Hills as early as 8500 calibrated years before present (cal. yrbp), following local deglaciation and the formation of the ice free area. This is the first report on the Holocene history of penguins in the Vestfold Hills. As in other areas of Antarctica, penguins occupied this area as soon as local ice retreated and the ice free area formed, and they are very sensitive to climatic and environmental changes. This work provides the foundation for understanding the history of penguins occupation in Vestfold Hills, East Antarctica.

Testing the synchronicity of Pleistocene biostratigraphic events in the central Arctic – Do we have a consistent biostratigraphic framework?  

2021 ◽  
Author(s):  
Flor Vermassen ◽  
Helen K. Coxall ◽  
Gabriel West ◽  
Matt O'Regan
Keyword(s):  
Arctic Ocean ◽  
Sediment Cores ◽  
Age Determination ◽  
The Arctic ◽  
Calcareous Nannofossils ◽  
Central Arctic Ocean ◽  
Eurasian Basin ◽  
Future Work ◽  
Amerasian Basin

<p>Harsh environmental and taphonomic conditions in the central Arctic Ocean make age-modelling for Quaternary palaeoclimate reconstructions challenging. Pleistocene age models in the Arctic have relied heavily on cyclostratigraphy using lithologic variability tied to relatively poorly calibrated foraminifera biostratigraphic events. Recently, the identification of <em>Pseudoemiliania lacunosa</em> in a sediment core from the Lomonosov Ridge, a coccolithophore that went extinct during marine isotope stage (MIS) 12 (478-424 ka), has been used to delineate glacial-interglacial units back to MIS 14 (~500 ka BP). Here we present a comparative study on how this nannofossil biostratigraphy fits with existing foraminifer biohorizons that are recognised in central Arctic Ocean sediments. A new core from the Alpha Ridge is presented, together with its lithologic variability and down-core compositional changes in planktonic and benthic foraminifera. The core exhibits an interval dominated by <em>Turborotalita egelida</em>, a planktonic foraminifer that is increasingly being adopted as a marker for MIS11 in sediment cores from the Amerasian Basin of the Arctic Ocean. We show that the new age-constraints provided by calcareous nannofossils are difficult to reconcile with the proposed MIS 11 age for the <em>T. egelida</em> horizon. Instead, the emerging litho- and coccolith biostratigraphy implies that Amerasian Basin sediments predating MIS5 are older than the egelida-based age models suggest, i.e. that the <em>T. egelida</em> Zone is older than MIS11. These results expose uncertainties regarding the age determination of glacial-interglacial cycles in the Amerasian basin and point out that future work is required to reconcile the micro- and nannofossil biostratigraphy of the Amerasian and Eurasian basin.</p>

scholarly journals Distribution of Natural Radioactivity,137Cs,90Sr, and Plutonium Isotopes in a Water Column and Sediment Core along the Algerian Coast

2007 ◽  
Vol 2007 ◽  
pp. 1-6 ◽  
Author(s):  
A. Noureddine ◽  
M. Benkrid ◽  
R. Maoui ◽  
M. Menacer ◽  
R. Boudjenoun
Keyword(s):  
Water Column ◽  
Sediment Core ◽  
Sediment Cores ◽  
Dry Weight ◽  
Artificial Radioactivity ◽  
Energy Agency ◽  
Area Of Interest ◽  
Algerian Coast ◽  
Seawater Samples ◽  
Thorium Series

Concentrations of natural (40K,210Pb, uranium, and thorium series) and artificial radioelements (137Cs,90Sr,239+240Pu) were determined in seawater and sediment samples collected from stations along the Algerian coast. Seawater was collected from the surface to a maximum depth of 2000 m; the sediment cores were sampled from a depth of around 1500 m. This work was carried out in August 2001, in the framework of the Regional African project /7/004 (RAF), by the accomplishment of an oceanographic campaign organized by the International Atomic Energy Agency (IAEA) in collaboration with Commissariat à l'Energie Atomique (COMENA) and L'Institut des Sciences de la Mer et de L'Amenagement du Littoral (ISMAL), on board of the research vessel of M.S. Benyahia of ISMAL. In addition to the record of the conductivity (mS) and temperature (°C) data at each station, seawater samples were treated and preconcentrated on board, those of sediment cores were divided into different layers in order to undergo analyses in the laboratory of radiological impact studies of Algiers. Concentration results were obtained for137Cs and90Sr in mBq/L and239+240Pu inμBq/L in seawater, and also for natural and artificial radionuclides in Bq/kg dry weight in the layers of the sediment cores. The different profiles of137Cs,239+240Pu,90Sr, and210Pb concentrations against depth were presented to show artificial radioactivity distribution in the water column and sediment core. Concentrations of137Cs in the sediment core were also used to identify the137Cs peak in the area of interest.

Late-Holocene evolution of a coastal lagoon in the Gulf of Lions (South of France)

2010 ◽  
Vol 181 (1) ◽  
pp. 27-36 ◽  
Author(s):  
Pierre Sabatier ◽  
Laurent Dezileau ◽  
Mickaël Barbier ◽  
Olivier Raynal ◽  
Johanna Lofi ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Coastal Lagoon ◽  
Late Holocene ◽  
Accumulation Rate ◽  
Sediment Cores ◽  
Coastal System ◽  
Gulf Of Lions ◽  
Marine Sand ◽  
Radiocarbon Data

Abstract The central part of the Gulf of Lions shoreline is characterized by many coastal wetlands that resulted from the interaction between a process of shoreline regularization by migrations of littoral barriers and a slow filling of the back-barrier areas by the riverine and marine inputs. Analyses of Late-Holocene deposits with a very high-resolution multi-proxy study of two sediment cores, allow us to reconstruct the evolution of this coastal system. Two main Holocene sediment units are identified overlying a Pliocene carbonate continental formation. The lower unit consists of sandy and pebbly marine sediments deposited around 7800 B.P., during the final stand of the last sea level rise. Just above, the upper unit displays lagoonal grey clay silts with shells and some intercalated layers of silty sands related to paleostorm events. The age model was established from radiocarbon dating, for the oldest part of the core. Over the last century, sedimentation rates were calculated using the CFCS 210Pb model, together with 137Cs data. Radiocarbon data show an increase in the accumulation rate from the base to the top of cores. Marine sand units related to the last transgressive deposit allow to refine the curve of Holocene post-glacial sea level rise. Sedimentological and faunal analyses associated with chronological data provide a means for reconstructing the Late-Holocene paleoenvironments along this part of the coast and suggest that the final closure of the coastal lagoon by the sandy barrier occurred at around 730 ± 120 yr cal B.P. The beginning of this closure, together with the progradation of the coastal plain, could be responsible for the decline in economic activity of the Lattara harbour during the Roman period.

scholarly journals Paleobiodiversity and Earth Science Paleoenvironmental Data

2019 ◽  
Vol 3 ◽  
Author(s):  
David Lazarus ◽  
Johan Renaudie
Keyword(s):  
Environmental Change ◽  
Sediment Core ◽  
Deep Sea ◽  
Earth Science ◽  
Sediment Cores ◽  
Science Data ◽  
Geologic Time ◽  
Occurrence Data ◽  
Earth Science Data ◽  
Global Data

Paleontology lies at the interface of earth sciences, biology and geologic time. When matched to histories of environmental change, such data is ideally suited to understanding how climate/environmental change affects biodiversity, and even how biodiversity change affects climate. Paleontologic and earth science collections, the data derived from them, and the global data infrastructures used in research are distinctively different than those in biology. Geologic time-linked earth science collections are found in geologic surveys, the oil industry and in museums as rock samples and sediment cores; paleontologic collections in museums and (via the microscopic fossils they contain) in sediment core repositories. Much published geologic time-linked earth science data is not tied to any collection material, and collected fossils are mostly only loosely linked to earth science collections or data. The exception is sediment cores and microfossils, where both earth science data and microfossil specimens are taken from the same cores and are thus tightly linked to each other. Lastly, most paleobiodiversity data used in research, even if derived from collection material, is compiled from the published literature rather than from collection databases. Three major types of linked earth science-paleontology data exist, each with its own data infrastructure. Very long time scale (Phanerozoic: 600 million years [myr]-Recent) but low time resolution (ca 10 myr) published fossil data is held in the Paleobiology Database [PBDB] and/or the Geobiodiversity Database [GBDB], together with very limited earth science data (mostly general rock type and approximate rock layer where found). PBDB in particular has been very successful in documenting the history of biodiversity over the last 600 my, and how a few major environmental events have affected it (mass extinctions and recoveries). Poor time resolution, taxonomic coarseness (most records are only for genera, not species) and poor links to earth science data have limited using this type of data for detailed studies of paleodiversity-environmental change. The NSB (formerly 'Neptune') database of deep-sea marine microfossils holds published fossil species occurrence data for the last ca 100 myr from the earth science sediment core collections of the deep-sea drilling programs [DSDP, ODP, IODP] together with detailed geochronologic data used to assign precise geologic ages to samples [.2-.02 myr resolution]. Species names are mostly linked to the separate community taxonomic catalog Mikrotax. All fossil occurrence data is also linked by sample name to the geologic core section material it was derived from. Earth history data from these core sections is not held in a central database, but a significant fraction is archived in the Pangea database, part of the ICSU World Data Center system. Biodiversity and environmental data can be linked directly via their shared sediment core sample locations, and/or by the high precision geologic ages for data in the systems. This type of data has been used to study biodiversity response to environmental change on many time and geographic scales, including rapid warming or cooling events, and response to major environmental catastrophes, e.g. the meteorite impact at the end of the Cretaceous. Lastly, very high temporal resolution (.01-.0001 my), mostly microfossil, plus earth-science data from land sections is held in the Neotoma system. This covers the last few my and is mostly used in local or regional studies of biodiversity and environmental change. New global data networking initiatives such as the Digital Deep Earth [DDE] initiative will create new opportunities to link earth science and biodiversity data to each other.

scholarly journals Last Glacial Maximum to Holocene paleoceanography of the northwestern Ross Sea inferred from sediment core geochemistry and micropaleontology at Hallett Ridge

2021 ◽  
Vol 40 (1) ◽  
pp. 15-35 ◽  
Author(s):  
Romana Melis ◽  
Lucilla Capotondi ◽  
Fiorenza Torricella ◽  
Patrizia Ferretti ◽  
Andrea Geniram ◽  
...  
Keyword(s):  
Sea Ice ◽  
Last Glacial Maximum ◽  
Sediment Core ◽  
Benthic Foraminifera ◽  
Ross Sea ◽  
Sediment Cores ◽  
Open Water ◽  
Glacial Maximum ◽  
Outer Continental Shelf ◽  
Last Glacial

Abstract. During the Late Pleistocene–Holocene, the Ross Sea Ice Shelf exhibited strong spatial variability in relation to the atmospheric and oceanographic climatic variations. Despite being thoroughly investigated, the timing of the ice sheet retreat from the outer continental shelf since the Last Glacial Maximum (LGM) still remains controversial, mainly due to a lack of sediment cores with a robust chronostratigraphy. For this reason, the recent recovery of sediments containing a continuous occurrence of calcareous foraminifera provides the important opportunity to create a reliable age model and document the early deglacial phase in particular. Here we present a multiproxy study from a sediment core collected at the Hallett Ridge (1800 m of depth), where significant occurrences of calcareous planktonic and benthic foraminifera allow us to document the first evidence of the deglaciation after the LGM at about 20.2 ka. Our results suggest that the co-occurrence of large Neogloboquadrina pachyderma tests and abundant juvenile forms reflects the beginning of open-water conditions and coverage of seasonal sea ice. Our multiproxy approach based on diatoms, silicoflagellates, carbon and oxygen stable isotopes on N. pachyderma, sediment texture, and geochemistry indicates that abrupt warming occurred at approximately 17.8 ka, followed by a period of increasing biological productivity. During the Holocene, the exclusive dominance of agglutinated benthic foraminifera suggests that dissolution was the main controlling factor on calcareous test accumulation and preservation. Diatoms and silicoflagellates show that ocean conditions were variable during the middle Holocene and the beginning of the Neoglacial period at around 4 ka. In the Neoglacial, an increase in sand content testifies to a strengthening of bottom-water currents, supported by an increase in the abundance of the tycopelagic fossil diatom Paralia sulcata transported from the coastal regions, while an increase in ice-rafted debris suggests more glacial transport by icebergs.

Intellectual analysis for testing of spacecraft onboard equipment

2019 ◽  
Author(s):  
О.С. Исаева ◽  
Л.Ф. Ноженкова ◽  
А.Ю. Колдырев
Keyword(s):  
Simulation Model ◽  
Knowledge Base ◽  
Model Comparison ◽  
Simulation Modelling ◽  
Logical Inference ◽  
First Case ◽  
Onboard System ◽  
The Given ◽  
Onboard Equipment

Показано применение прецедентов функционирования имитационной модели для анализа результатов испытаний бортовой аппаратуры космического аппарата. Прецеденты содержат различные сценарии передачи команд управления и соответствующие им варианты изменения параметров телеметрии бортовых систем космического аппарата. Сценарии описываются правилами базы знаний и моделируются процедурами логического вывода. Разработанные структуры данных и программное обеспечение позволяют выполнять имитационные эксперименты, сохранять результаты в базе прецедентов и сопоставлять их с результатами испытаний бортовых систем как в процессе выполнения испытательных процедур, так и ретроспективно. Применение результатов имитационного моделирования расширяет возможности испытательного программного обеспечения и способствует повышению качества конструкторских решений. This article represents a method for intellectual analysis of the results of testing spacecraft onboard equipment on the bases of the precedents of the simulation model. A simulation model is founded on a knowledge base describing different peculiar properties of the onboard equipment’s function, settings of the reception-transmission tract, scenarios of control commands’ transmission and corresponding changes of the parameters of onboard devices’ telemetry. We have designed data structures and software that allows conducting simulation experiments, save them in the precedent base and compare the results of the simulation modelling with the results of the onboard system’s testing. This analysis is carried out both during tests and after they are finished. In the first case, an onboard systems’ command is sent to the object of testing and to the simulation model. The model contains methods of logical inference that forms a conflict set of rules, choose and complete the applied actions simulating the functions of onboard equipment at reception and execution of the given commands. The results of modelling are represented in telemetry that is compared with the telemetry received from the objects of testing. A designer is given a list of parameters that were changed in the process of the logical inference and the telemetry parameters of the object of testing. In the other case, the telemetry of the onboard system obtained from the test storage results is compared with the precedents of the simulation model from the data base. Precedents contain examples of execution of big variety of commands and sets of the rules of the knowledge base that were completed for their acquisition. If telemetry parameters coincide, software allows a step-by-step review of the tests thus making a comparison with the actions of the simulation model. Comparison of the simulation model precedents with the results of testing allows revealing special features of the onboard equipment function that may remain unnoticed when other methods of analysis are utilized. Intellectual methods of logical output for analysis of tests extend the capabilities of test software and provide better quality of designer solutions.

scholarly journals The origin of methane in the East Siberian Arctic Shelf unraveled with triple isotope analysis

2017 ◽  
Vol 14 (9) ◽  
pp. 2283-2292 ◽  
Author(s):  
Célia J. Sapart ◽  
Natalia Shakhova ◽  
Igor Semiletov ◽  
Joachim Jansen ◽  
Sönke Szidat ◽  
...  
Keyword(s):  
Isotope Composition ◽  
Sediment Cores ◽  
Isotope Analysis ◽  
Age Determination ◽  
Unknown Origin ◽  
Arctic Shelf ◽  
The Arctic ◽  
Small Contribution ◽  
Siberian Arctic ◽  
Subsea Permafrost

Abstract. The Arctic Ocean, especially the East Siberian Arctic Shelf (ESAS), has been proposed as a significant source of methane that might play an increasingly important role in the future. However, the underlying processes of formation, removal and transport associated with such emissions are to date strongly debated. CH4 concentration and triple isotope composition were analyzed on gas extracted from sediment and water sampled at numerous locations on the shallow ESAS from 2007 to 2013. We find high concentrations (up to 500 µM) of CH4 in the pore water of the partially thawed subsea permafrost of this region. For all sediment cores, both hydrogen and carbon isotope data reveal the predominant occurrence of CH4 that is not of thermogenic origin as it has long been thought, but resultant from microbial CH4 formation. At some locations, meltwater from buried meteoric ice and/or old organic matter preserved in the subsea permafrost were used as substrates. Radiocarbon data demonstrate that the CH4 present in the ESAS sediment is of Pleistocene age or older, but a small contribution of highly 14C-enriched CH4, from unknown origin, prohibits precise age determination for one sediment core and in the water column. Our sediment data suggest that at locations where bubble plumes have been observed, CH4 can escape anaerobic oxidation in the surface sediment.

scholarly journals SARS-CoV-2 Spread Forecast Dynamic Model Validation through Digital Twin Approach, Catalonia Case Study

Mathematics ◽  
2021 ◽  
Vol 9 (14) ◽  
pp. 1660
Author(s):  
Pau Fonseca i Casas ◽  
Joan Garcia i Subirana ◽  
Víctor García i Carrasco ◽  
Xavier Pi i Palomés
Keyword(s):  
Model Comparison ◽  
Dynamic Models ◽  
Complex Nature ◽  
Description Language ◽  
Digital Twin ◽  
Modeling Process ◽  
Lack Of Information ◽  
Comparison Approach ◽  
Nonpharmaceutical Interventions

The spread of the SARS-CoV-2 modeling is a challenging problem because of its complex nature and lack of information regarding certain aspects. In this paper, we explore a Digital Twin approach to model the pandemic situation in Catalonia. The Digital Twin is composed of three different dynamic models used to perform the validations by a Model Comparison approach. We detail how we use this approach to obtain knowledge regarding the effects of the nonpharmaceutical interventions and the problems we faced during the modeling process. We use Specification and Description Language (SDL) to represent the compartmental forecasting model for the SARS-CoV-2. Its graphical notation simplifies the different specialists’ understanding of the model hypotheses, which must be validated continuously following a Solution Validation approach. This model allows the successful forecasting of different scenarios for Catalonia. We present some formalization details, discuss the validation process and present some results obtained from the validation model discussion, which becomes a digital twin of the pandemic in Catalonia.

scholarly journals Hipercorig – an innovative hydraulic coring system recovering over 60 m long sediment cores from deep perialpine lakes

2020 ◽  
Vol 28 ◽  
pp. 29-41
Author(s):  
Ulrich Harms ◽  
Ulli Raschke ◽  
Flavio S. Anselmetti ◽  
Michael Strasser ◽  
Volker Wittig ◽  
...  
Keyword(s):  
Sediment Cores ◽  
Lacustrine Sediments ◽  
Novel Technology ◽  
Perialpine Lakes ◽  
Northern Edge ◽  
Alpine Foreland ◽  
Main Barrier ◽  
Core Description ◽  
Lake Systems ◽  
Marine Basins

Abstract. The record of past environmental conditions and changes archived in lacustrine sediments serves as an important element in paleoenvironmental and climate research. A main barrier in accessing these archives is the undisturbed recovery of long cores from deep lakes. In this study, we have developed and tested a new, environmentally friendly coring tool and modular barge, centered around a down-the-hole hydraulic hammering of an advanced piston coring system, called the Hipercorig. Test beds for the evaluation of the performance of the system were two periglacial lakes, Mondsee and Constance, located on the northern edge of the Alpine chain. These lakes are notoriously difficult to sample beyond ∼ 10 m sediment depths due to dense glacial deposits obstructing deeper coring. Both lakes resemble many global lake systems with hard and coarse layers at depth, so the gained experience using this novel technology can be applied to other lacustrine or even marine basins. These two experimental drilling projects resulted in up to 63 m coring depth and successful coring operations in up to 204 m water depth, providing high-quality, continuous cores with 87 % recovery. Initial core description and scanning of the 63 m long core from Mondsee and two 20 and 24 m long cores from Lake Constance provided novel insights beyond the onset of deglaciation of the northern Alpine foreland dating back to ∼ 18 400 cal BP.

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