scholarly journals Synchronizing early Eocene deep-sea and continental records – cyclostratigraphic age models for the Bighorn Basin Coring Project drill cores

2018 ◽  
Vol 14 (3) ◽  
pp. 303-319 ◽  
Author(s):  
Thomas Westerhold ◽  
Ursula Röhl ◽  
Roy H. Wilkens ◽  
Philip D. Gingerich ◽  
William C. Clyde ◽  
...  
Keyword(s):  
Deep Sea ◽  
Large Scale ◽  
Major Change ◽  
Terrestrial Ecosystems ◽  
Geochemical Data ◽  
Bighorn Basin ◽  
Early Eocene ◽  
Thermal Maximum ◽  
The Impact ◽  
Drill Cores

Abstract. A consistent chronostratigraphic framework is required to understand the effect of major paleoclimate perturbations on both marine and terrestrial ecosystems. Transient global warming events in the early Eocene, at 56–54 Ma, show the impact of large-scale carbon input into the ocean–atmosphere system. Here we provide the first timescale synchronization of continental and marine deposits spanning the Paleocene–Eocene Thermal Maximum (PETM) and the interval just prior to the Eocene Thermal Maximum 2 (ETM-2). Cyclic variations in geochemical data come from continental drill cores of the Bighorn Basin Coring Project (BBCP, Wyoming, USA) and from marine deep-sea drilling deposits retrieved by the Ocean Drilling Program (ODP). Both are dominated by eccentricity-modulated precession cycles used to construct a common cyclostratigraphic framework. Integration of age models results in a revised astrochronology for the PETM in deep-sea records that is now generally consistent with independent 3He age models. The duration of the PETM is estimated at ∼ 200 kyr for the carbon isotope excursion and ∼ 120 kyr for the associated pelagic clay layer. A common terrestrial and marine age model shows a concurrent major change in marine and terrestrial biota ∼ 200 kyr before ETM-2. In the Bighorn Basin, the change is referred to as Biohorizon B and represents a period of significant mammalian turnover and immigration, separating the upper Haplomylus–Ectocion Range Zone from the Bunophorus Interval Zone and approximating the Wa-4–Wa-5 land mammal zone boundary. In sediments from ODP Site 1262 (Walvis Ridge), major changes in the biota at this time are documented by the radiation of a “second generation” of apical spine-bearing sphenolith species (e.g., S. radians and S. editus), the emergence of T. orthostylus, and the marked decline of D. multiradiatus.

scholarly journals Synchronizing early Eocene deep-sea and continental records – new cyclostratigraphic age models from the Bighorn Basin Coring Project

2017 ◽  
Author(s):  
Thomas Westerhold ◽  
Ursula Röhl ◽  
Roy Wilkens ◽  
Philip D. Gingerich ◽  
Will Clyde ◽  
...  
Keyword(s):  
Deep Sea ◽  
Large Scale ◽  
Major Change ◽  
Terrestrial Ecosystems ◽  
Geochemical Data ◽  
Bighorn Basin ◽  
Early Eocene ◽  
Ocean Drilling Program ◽  
Thermal Maximum ◽  
The Impact

Abstract. A consistent stratigraphic framework is required to understand the effect of major climate perturbations of the geological past on both marine and terrestrial ecosystems. Transient global warming events in the early Eocene, 56–54 Ma ago, show the impact of large scale input of carbon into the ocean-atmosphere system. Here we provide the first time-scale synchronization of continental and marine deposits spanning the Paleocene-Eocene Thermal Maximum (PETM) and the interval just prior to the Eocene Thermal Maximum 2 (ETM-2). Cyclic variations in geochemical data come from continental drill cores of the Bighorn Basin Drilling Project (BBCP, Wyoming, USA) and from marine deep-sea drilling deposits retrieved by the Ocean Drilling Program (ODP). Both are dominated by eccentricity modulated precession cycles that are used to construct a common cyclostratigraphic framework. Integration of age models results in a revised astrochronology for the PETM in deep-sea records that is now generally consistent with independent 3He age models. The duration of the PETM is estimated at ~ 200 kyr for the CIE and ~ 120 kyr for the pelagic clay layer. A common terrestrial and marine age model shows a concurrent major change in marine and terrestrial biotas ~ 200 kyr before ETM-2. In the Bighorn Basin, the change is referred to as Biohorizon B, and it represents a period of significant mammalian turnover and immigration, separating the upper Haplomylus-Ectocion Range Zone from the Bunophorus Interval Zone and approximating the Wa-4–Wa-5 land mammal zone boundary. In sediments from ODP Site 1262 (Walvis Ridge), major changes in the biota at this time are documented by the radiation of a 2nd generation of apical spine-bearing sphenoliths species (e.g., S. radians and S. editus), the emergence of T. orthostylus, and the marked decline of D. multiradiatus.

scholarly journals Remote sensing of the impact of flash drought events on terrestrial carbon dynamics over China

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Miao Zhang ◽  
Xing Yuan ◽  
Jason A. Otkin
Keyword(s):  
Remote Sensing ◽  
Soil Moisture ◽  
Large Scale ◽  
Structural Changes ◽  
Terrestrial Ecosystems ◽  
Northern China ◽  
Carbon Dynamics ◽  
Western China ◽  
Terrestrial Carbon ◽  
The Impact

Abstract Background Flash drought poses a great threat to terrestrial ecosystems and influences carbon dynamics due to its unusually rapid onset and increasing frequency in a warming climate. Understanding the response of regional terrestrial carbon dynamics to flash drought requires long-term observations of carbon fluxes and soil moisture at a large scale. Here, MODIS satellite observations of ecosystem productivity and ERA5 reanalysis modeling of soil moisture are used to detect the response of ecosystems to flash drought over China. Results The results show that GPP, NPP, and LAI respond to 79–86% of the flash drought events over China, with highest and lowest response frequency for NPP and LAI, respectively. The discrepancies in the response of GPP, NPP, and LAI to flash drought result from vegetation physiological and structural changes. The negative anomalies of GPP, NPP, and LAI occur within 19 days after the start of flash drought, with the fastest response occurring over North China, and slower responses in southern and northeastern China. Water use efficiency (WUE) is increased in most regions of China except for western regions during flash drought, illustrating the resilience of ecosystems to rapid changes in soil moisture conditions. Conclusions This study shows the rapid response of ecosystems to flash drought based on remote-sensing observations, especially for northern China with semiarid climates. Besides, NPP is more sensitive than GPP and LAI to flash drought under the influence of vegetation respiration and physiological regulations. Although the mean WUE increases during flash drought over most of China, western China shows less resilience to flash drought with little changes in WUE during the recovery stage. This study highlights the impacts of flash drought on ecosystems and the necessity to monitor rapid drought intensification.

scholarly journals Paleoenvironmental response of midlatitudinal wetlands to Paleocene–early Eocene climate change (Schöningen lignite deposits, Germany)

2019 ◽  
Vol 15 (5) ◽  
pp. 1741-1755 ◽  
Author(s):  
Katharina Methner ◽  
Olaf Lenz ◽  
Walter Riegel ◽  
Volker Wilde ◽  
Andreas Mulch
Keyword(s):  
Carbon Isotope ◽  
North Sea ◽  
Terrestrial Ecosystems ◽  
High Pco2 ◽  
Organic Carbon Content ◽  
Early Eocene ◽  
Thermal Maximum ◽  
Early Paleogene ◽  
Sea Coast ◽  
North Sea Coast

Abstract. The early Paleogene is marked by multiple negative carbon isotope excursions (CIEs) that reflect massive short-term carbon cycle perturbations that coincide with significant warming during a high-pCO2 world, affecting both marine and terrestrial ecosystems. Records of such hyperthermals from the marine–terrestrial interface (e.g., estuarine swamps and mire deposits) are therefore of great interest as their present-day counterparts are highly vulnerable to future climate and sea level change. Here, we assess paleoenvironmental changes of midlatitudinal late Paleocene–early Eocene peat mire records along the paleo-North Sea coast. We provide carbon isotope data of bulk organic matter (δ13CTOC), organic carbon content (%TOC), and palynological data from an extensive peat mire deposited at a midlatitudinal (ca. 41∘ N) coastal site (Schöningen, Germany). The δ13CTOC data show a carbon isotope excursion of −1.3 ‰ (mean decrease in δ13CTOC; −1.7 ‰ at the onset of CIE) coeval with a conspicuous Apectodinium acme. Due to the exceptionally large stratigraphic thickness of the CIE at Schöningen (10 m of section) we established a detailed palynological record that indicates only minor changes in paleovegetation leading into and during this event. Instead, paleovegetation changes mostly follow natural successions in response to changes along the marine–terrestrial interface. The available age constraints for the Schöningen Formation hamper a solid assignment of the detected CIE to a particular hyperthermal such as the Paleocene–Eocene Thermal Maximum (PETM) or any succeeding hyperthermal event such as the Eocene Thermal Maximum 2 (ETM2). Compared to other nearby peat mire records (Cobham, UK; Vasterival, F) it appears that wetland deposits around the Paleogene North Sea have a consistent CIE magnitude of ca. −1.3 ‰ in δ13CTOC. Moreover, the Schöningen record shares major characteristics with the Cobham Lignite PETM record, including evidence for increased fire activity prior to the CIE, minor plant species change during the hyperthermal, a reduced CIE in δ13CTOC, and drowning of the mire (marine ingressions) during much of the Schöningen CIE event. This suggests that either the Schöningen CIE reflects the PETM or that early Paleogene hyperthermals similarly affected paleoenvironmental conditions of a major segment of the paleo-North Sea coast.

Terrestrial and extraterrestrial chemical components of early Archean impact spherule layers from Fairview Gold Mine, northern Barberton greenstone belt, South Africa

2021 ◽  
Author(s):  
Grace Juliana Gonçalves de Oliveira ◽  
Wolf Uwe Reimold ◽  
Álvaro Penteado Crósta ◽  
Natalia Hauser ◽  
Christian Koeberl ◽  
...  
Keyword(s):  
South Africa ◽  
Greenstone Belt ◽  
Large Scale ◽  
Chemical Components ◽  
Gold Mine ◽  
Barberton Greenstone Belt ◽  
Stratigraphic Position ◽  
Exploration Drilling ◽  
The Impact ◽  
Drill Cores

ABSTRACT Early Archean spherule layers, widely accepted to represent distal ejecta deposits from large-scale impact events onto the early Earth, have been described from several stratigraphic levels of the Barberton greenstone belt in South Africa. Recently, exploration drilling at the Fairview Gold Mine (25°43′53″S, 31°5′59″E) in the northern domain of the belt resulted in the discovery of a new set of spherule layer intersections. The Fairview spherule layers in drill cores BH5901, BH5907, BH5911, and BH5949 were intersected just a few meters apart, at about the same stratigraphic position within the transition from the Onverwacht Group to the Fig Tree Group. The Fairview spherule layers have petrographic and chemical similarities to at least three other well-known Barberton spherule layers (S2–S4), and multiple spherule layer bed intersections in drill cores BARB5 and CT3, all from about the same stratigraphic position. They are not uniform in composition, in particular with respect to abundances of highly siderophile elements. The highest concentrations of moderately (Cr, Co, Ni) and highly siderophile (Ir) elements are within the range of concentrations for chondrites and, thus, reinforce the impact hypothesis for the generation of the Fairview spherule layers. Iridium peak concentrations and Cr/Ir interelement ratios for spherule layer samples from drill cores BH5907, BH5911, and BH5949 suggest admixtures of 50%–60% chondritic material, whereas for the BH5901 spherule layer, only an admixture of 1% chondritic material is indicated. We discuss whether these four Fairview spherule layers represent the same impact event, and whether they can be correlated to any of the S2–S4, CT3, and BARB5 intersections.

scholarly journals Mammal faunal response to the Paleogene hyperthermals ETM2 and H2

2015 ◽  
Vol 11 (2) ◽  
pp. 1371-1405
Author(s):  
A. E. Chew
Keyword(s):  
Climate Change ◽  
Global Warming ◽  
Bighorn Basin ◽  
Early Eocene ◽  
The South ◽  
Deep Time ◽  
Early Eocene Climatic Optimum ◽  
South Central ◽  
Species Vulnerability ◽  
Thermal Maximum

Abstract. Scientists are increasingly turning to deep-time fossil records to decipher the long-term consequences of climate change in the race to preserve modern biotas from anthropogenically driven global warming. "Hyperthermals" are past intervals of geologically rapid global warming that provide the opportunity to study the effects of climate change on existing faunas over thousands of years. A series hyperthermals is known from the early Eocene (∼56–54 million years ago), including the Paleocene-Eocene Thermal Maximum (PETM) and two subsequent hyperthermals, Eocene Thermal Maximum 2 (ETM2) and H2. The later hyperthermals occurred following the onset of warming at the Early Eocene Climatic Optimum (EECO), the hottest sustained period of the Cenozoic. The PETM has been comprehensively studied in marine and terrestrial settings, but the terrestrial biotic effects of ETM2 and H2 are unknown. Their geochemical signatures have been located in the northern part of the Bighorn Basin, WY, USA, and their levels can be extrapolated to an extraordinarily dense, well-studied terrestrial mammal fossil record in the south-central part of the basin. High-resolution, multi-parameter paleoecological analysis reveals significant peaks in species diversity and turnover and changes in abundance and relative body size at the levels of ETM2 and H2 in the south-central Bighorn Basin record. In contrast with the PETM, faunal change at the later hyperthermals is less extreme, does not include immigration and involves a proliferation of body sizes, although abundance shifts tend to favor smaller congeners. Faunal response at ETM2 and H2 is distinctive in its high proportion of species losses potentially related to heightened species vulnerability in response to the changes already underway at the beginning of the EECO. Faunal response at ETM2 and H2 is also distinctive in high proportions of beta richness, suggestive of increased geographic dispersal related to transient increases in habitat (floral) complexity and/or precipitation or seasonality of precipitation. These results suggest that rapid ecological changes, increased heterogeneity in species incidence, and heightened species vulnerability and loss may be expected across most of North America in the near future in response to anthropogenically-driven climate change.

scholarly journals Overview of the fire management policy of the Kruger National Park

Koedoe ◽  
1999 ◽  
Vol 42 (1) ◽  
Author(s):  
H.C. Biggs ◽  
A.L.F. Potgieter
Keyword(s):  
National Park ◽  
Large Scale ◽  
Fire Management ◽  
Major Change ◽  
Management Plan ◽  
Kruger National Park ◽  
Management Policy ◽  
Fire Policy ◽  
Trade Offs ◽  
The Impact

New developments in fire management policy in the Kruger National Park are sketched against the background of changing attitudes towards ecosystem management. The experimental burning plots established in the mid-1950s are discussed briefly, as is the almost forty-year era of rotational block- burning. The lightning-driven fire policy initiated in 1992 and currently aimed at by park management is discussed, with comments on its early performance. More recent revision of the management plan stressed maximisation of appropriate research benefits from the experimental burning plots, con- doned the lightning approach for the present, but stressed the absolute necessity of the park not finding itself in the 1992 position again, where a major change in policy has to be made with no comparative evidence from other systems. To this end, a major landscape-scale fire management trial has been planned for implementation starting in April 2000. It is sheduled to run over a twenty-year period, and will be placed at four localities representing different major landscapes in the park. It will compare the effects of three different fire systems (lightning, patch mosaic, and range condition burning systems) on biodiversity elements crucial to the park's mission. The rationale for, layout of, and criteria for deciding on the outcome of the trial are discussed, as well as the trade-offs that were made to enable the trial to be of such a large scale and still fit into overall park planning. The impact of the trial on the park's monitoring programme is discussed.

scholarly journals The impact of atmospheric CO<sub>2</sub> and N management on simulated yields and tissue C : N in the main wheat regions of Western Europe

2015 ◽  
Vol 12 (2) ◽  
pp. 1047-1111
Author(s):  
S. Olin ◽  
G. Schurgers ◽  
M. Lindeskog ◽  
D. Wårlind ◽  
B. Smith ◽  
...  
Keyword(s):  
Large Scale ◽  
Western Europe ◽  
Crop Yields ◽  
Model Performance ◽  
Co2 Enrichment ◽  
Terrestrial Ecosystems ◽  
Plant Interactions ◽  
C Cycle ◽  
Managed Ecosystems ◽  
The Impact

Abstract. Nitrogen (N) is a key element in terrestrial ecosystems as it influences both plant growth and plant interactions with the atmosphere. Accounting for carbon-nitrogen interactions has been found to alter future projections of the terrestrial carbon (C) cycle substantially. Dynamic vegetation models (DVMs) aim to accurately represent both natural vegetation and managed land, not only from a carbon cycle perspective but increasingly so also for a wider range of processes including crop yields. We present here the extended version of the DVM LPJ-GUESS that accounts for N limitation in crops to account for the effects of N fertilisation on yields and biogeochemical cycling. The performance of this new implementation is evaluated against observations from N fertiliser trials and CO2 enrichment experiments. LPJ-GUESS captures the observed response to both N and CO2 fertilization on wheat biomass production, tissue C to N ratios (C : N) and phenology. To test the model's applicability for larger regions, simulations are subsequently performed that cover the wheat-dominated regions of Western Europe. When compared to regional yield statistics, the inclusion of C–N dynamics in the model substantially increase the model performance compared to an earlier version of the model that does not account for these interactions. For these simulations, we also demonstrate an implementation of N fertilisation timing for areas where this information is not available. This feature is crucial when accounting for processes in managed ecosystems in large-scale models. Our results highlight the importance of accounting for C–N interactions when modelling agricultural ecosystems, and it is an important step towards accounting for the combined impacts of changes in climate, [CO2] and land use on terrestrial biogeochemical cycles.

scholarly journals Effects of Climate Factors and Human Activities on the Ecosystem Water Use Efficiency throughout Northern China

2019 ◽  
Vol 11 (23) ◽  
pp. 2766 ◽  
Author(s):  
Xiaozheng Du ◽  
Xiang Zhao ◽  
Tao Zhou ◽  
Bo Jiang ◽  
Peipei Xu ◽  
...  
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Human Activities ◽  
Large Scale ◽  
Terrestrial Ecosystems ◽  
Northern China ◽  
Climate Factors ◽  
Ecosystem Water Use Efficiency ◽  
Use Efficiency ◽  
The Impact

Global climate changes have increased the imbalance of water resources, especially in northern China, which comprises typical arid and semiarid regions. Large-scale afforestation has been implemented over the past three decades in northern China. The ecosystem water use efficiency (WUE) connects the carbon cycle and water cycle of the terrestrial ecosystems and is defined as the ratio of the gross primary productivity (GPP) to the evapotranspiration. However, there are still an insufficient number of studies on the impact of the afforestation on the WUE. In this study, we applied the random forest (RF) model to explore the impacts of climate and nonclimate factors on the WUE in northern China. The results showed that in areas with high precipitation, the forests had the highest WUE, while in the arid areas, the croplands had the highest WUE. Of the total area, 44.34% showed a significant increase, and 5.89% showed a significant decrease in the WUE from 1982–2015 in northern China. The main driving factors for the changes in the WUE were climate factors, including the precipitation, temperature and solar radiation, which contributed to approximately 84% of the WUE trends, while human activities, such as afforestation, contributed to approximately 16% of the WUE trends. Overall, although the climate had a larger impact on the WUE dynamics than the human activities, our results suggested that the impacts of the afforestation programs on forest carbon and water cycles should be considered in the context of climate change.

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