Sea level and astronomically induced environmental changes in Middle and Late Eocene sediments from the East Tasman Plateau

2004 ◽  
pp. 127-151 ◽  
Author(s):  
Ursula Röhl ◽  
Henk Brinkhuis ◽  
Catherine E. Stickley ◽  
Mike Fuller ◽  
Stephen A. Schellenberg ◽  
...  
Keyword(s):  
Sea Level ◽  
Environmental Changes ◽  
Late Eocene

Periodically forced self-organization in the long-term evolution of planktic foraminifera

2001 ◽  
Vol 38 (2) ◽  
pp. 293-308 ◽  
Author(s):  
Andreas Prokoph ◽  
Anthony D Fowler ◽  
R Timothy Patterson
Keyword(s):  
Sea Level ◽  
Logistic Map ◽  
Late Eocene ◽  
Self Organization ◽  
Extinction Data ◽  
Sea Level Fluctuations ◽  
Global Sea Level ◽  
Extinction Events ◽  
The Impact

Wavelet transform and other signal analysis techniques suggest that the planktic foraminiferal (PF) long-term evolutionary record of the last 127 Ma can be attributed to complex periodic and nonlinear patterns. Correlation of the PF extinction pattern with other geological series favors an origin of the ~30 Ma periodicity and self-organization by quasi-periodic mantle-plume cycles that in turn drive episodic volcanism, CO2-degassing, oceanic anoxic conditions, and sea-level fluctuations. Stationary ~30 Ma periodicity and a weak secular trend of ~100 Ma period are evident in the PF record, even without consideration of the mass extinction at the K–T boundary. The 27–32 Ma periodicity in the impact crater record and lows in the global sea-level curve, respectively, are ~6.5 Ma and ~2.3 Ma out of phase with PF-extinction data, although major PF-extinction events correspond to the bolide impacts at the K–T boundary and in late Eocene. Another six extinction events correspond to abrupt global sea-level falls between the late Albian and early Oligocene. Self-organization in the PF record is characterized by increased radiation rates after major extinction events and a steady number of baseline species. Our computer model of long-term PF evolution replicates this SO pattern. The model consists of output from the logistic map, which is forced at 30 Ma and 100 Ma frequencies. The model has significant correlations with the relative PF-extinction data. In particular, it replicates singularities, such as the K–T event, nonstationary 2.5–10 Ma periodicities, and phase shifts in the ~30 Ma periodicity of the PF record.

scholarly journals Holocene sea level and climate interactions on wet dune slack evolution in SW Portugal: A model for future scenarios?

The Holocene ◽  
2018 ◽  
Vol 29 (1) ◽  
pp. 26-44 ◽  
Author(s):  
Manel Leira ◽  
Maria C Freitas ◽  
Tania Ferreira ◽  
Anabela Cruces ◽  
Simon Connor ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Environmental Changes ◽  
Sediment Accumulation ◽  
High Energy ◽  
Sediment Supply ◽  
Dune Slack ◽  
Ecological Stability ◽  
The Holocene ◽  
Climate Interactions

We examine the Holocene environmental changes in a wet dune slack of the Portuguese coast, Poço do Barbarroxa de Baixo. Lithology, organic matter, biological proxies and high-resolution chronology provide estimations of sediment accumulation rates and changes in environmental conditions in relation to sea-level change and climate variability during the Holocene. Results show that the wet dune slack was formed 7.5 cal. ka BP, contemporaneous with the last stages of the rapid sea-level rise. This depositional environment formed under frequent freshwater flooding and water ponding that allowed the development and post-mortem accumulation of abundant plant remains. The wetland evolved into mostly palustrine conditions over the next 2000 years, until a phase of stabilization in relative sea-level rise, when sedimentation rates slowed down to 0.04 mm yr−1, between 5.3 and 2.5 cal. ka BP. Later, about 0.8 cal. ka BP, high-energy events, likely due to enhanced storminess and more frequent onshore winds, caused the collapse of the foredune above the wetlands’ seaward margin. The delicate balance between hydrology (controlled by sea-level rise and climate change), sediment supply and storminess modulates the habitat’s resilience and ecological stability. This underpins the relevance of integrating past records in coastal wet dune slacks management in a scenario of constant adaptation processes.

scholarly journals Reef development and Sea level changes drive Acanthaster Population Expansion in the Indo-Pacific region

2020 ◽  
Author(s):  
P.C. Pretorius ◽  
T.B. Hoareau
Keyword(s):  
Population Size ◽  
Sea Level ◽  
Environmental Changes ◽  
Sequence Data ◽  
Demographic History ◽  
Population Expansion ◽  
Population Level ◽  
Sea Level Changes ◽  
Reef Development ◽  
Curve Fitting Method

AbstractMolecular clock calibration is central in population genetics as it provides an accurate inference of demographic history, whereby helping with the identification of driving factors of population changes in an ecosystem. This is particularly important for coral reef species that are seriously threatened globally and in need of conservation. Biogeographic events and fossils are the main source of calibration, but these are known to overestimate timing and parameters at population level, which leads to a disconnection between environmental changes and inferred reconstructions. Here, we propose the Last Glacial Maximum (LGM) calibration that is based on the assumptions that reef species went through a bottleneck during the LGM, which was followed by an early yet marginal increase in population size. We validated the LGM calibration using simulations and genetic inferences based on Extended Bayesian Skyline Plots. Applying it to mitochondrial sequence data of crown-of-thorns starfish Acanthaster spp., we obtained mutation rates that were higher than phylogenetically based calibrations and varied among populations. The timing of the greatest increase in population size differed slightly among populations, but all started between 10 and 20 kya. Using a curve-fitting method, we showed that Acanthaster populations were more influenced by sea-level changes in the Indian Ocean and by reef development in the Pacific Ocean. Our results illustrate that the LGM calibration is robust and can probably provide accurate demographic inferences in many reef species. Application of this calibration has the potential to help identify population drivers that are central for the conservation and management of these threatened ecosystems.

scholarly journals Graptolite dynamics in Silurian and Devonian time

1987 ◽  
Vol 35 ◽  
pp. 149-159
Author(s):  
T. N. Koren'
Keyword(s):  
Environmental Factors ◽  
Sea Level ◽  
Comparative Studies ◽  
Climate Changes ◽  
Environmental Changes ◽  
Time Intervals ◽  
Early Devonian ◽  
Carbonate Sedimentation ◽  
Reference Sections ◽  
Devonian Age

On the basis of biostratigraphic data known at present some preliminary attempts are made to evaluate graptolite dynamics, that is changes in graptolite diversity in time and space within pelagic fades of Si­lurian and Early Devonian age. For the comparative studies of diversity fluctuations versus some major environmental changes a standard graptolite zonation is used. Several critical and more or less well stu­died stratigraphical intervals are chosen; among them the Ordovician/Silurian, Sheinwoodian/Gorstian and Gorstian/Ludfordian boundary beds. For each level the most complete reference sections are analy­zed. Special attention is given to the graptolite extinction, specification and radiation events within these time intervals. They might have been partly connected with or influenced by the environmental factors as a result of eustatic sea-level and climate changes, alteration of anoxic conditions, migration of carbonate sedimentation in pelagic direction, and other globally detectable events. The graptolite evolution during the time of monograptid existence can be subdivided into three phases using the comparison of the ampli­tude of the extinction-origination events and repeatability of the synphasic cycles.

scholarly journals Paleotemperature and paleosalinity evolution across Eocene-Oligocene Transition in North Atlantic Ocean: Insights from geochemical analysis of bivalve shells.

2020 ◽  
Author(s):  
Justine Briard ◽  
Marc de Rafélis ◽  
Emmanuelle Vennin ◽  
Mathieu Daëron ◽  
Valérie Chavagnac ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Sea Level ◽  
Environmental Changes ◽  
North Atlantic Ocean ◽  
Global Climate ◽  
Ice Sheet ◽  
Major Step ◽  
Mode Identification ◽  
Global Climate Changes ◽  
Bivalve Shells

<p>The Cenozoic period encompasses the last transition from the “greenhouse” climate of the late Early Eocene (~50 Ma) to our modern “icehouse” climate with its much lower CO<sub>2</sub> levels, significant polar glaciation and major sea level drop. The Eocene-Oligocene transition (EOT), that marks the first major ice-sheet build-up on Antarctica, has been extensively studied as it represents the entrance into an icehouse mode. Identification of this major step of Antarctic ice-sheet build-up strongly relies on δ<sup>18</sup>O and Mg/Ca benthic foraminifera records from ODP / DSDP sites. By contrast, few records currently exist from coastal environments despite the presence of abundant fossil archives, like bivalve shells. Yet palaeoenvironmental records from these peculiar coastal sites could bring information on how they react to global climate changes and help to further understand the behavior of our climate system. In this study, we applied a multi-proxy strategy coupling δ<sup>18</sup>O, δ<sup>13</sup>C, clumped isotopes (Δ<sub>47</sub>), strontium isotopes (<sup>87</sup>Sr/<sup>86</sup>Sr) analyses on aragonitic and calcitic bivalves and sediments recovered from the Isle of Wight (London-Paris Basin, Northeastern Atlantic Ocean) to provide additional constrain on environmental changes in this region across the Eocene-Oligocene Transition (~37.8–33 Ma).</p><p>Our new coupled δ<sup>18</sup>O and Δ<sub>47 </sub>dataset highlights a marked decrease in local seawater temperatures (~ 8°C) coupled to a drop in local seawater δ<sup>18</sup>O, likely linked to the sea level drop associated with ice-cap formation and an evolution toward more proximal, brackish environment in this region (that is apparent from sediment facies evolution). We estimate the salinity decrease recorded at the local scale from the Eocene to the Oligocene as reaching about 6 PSU, from 31 to 25 PSU. Strontium isotope analyses of the bivalves support this interpretation, showing values close to that of seawater up to the EOT but a marked deviation from contemporaneous global seawater <sup>87</sup>Sr/<sup>86</sup>Sr values toward more radiogenic values afterward. This positive deviation is in agreement with an evolution toward more proximal environments, subjected to larger freshwater inputs.</p>

Continental temperature seasonality from Eocene Warmhouse to Oligocene Coolhouse — A model-data comparison

2021 ◽  
Author(s):  
Agathe Toumoulin ◽  
Yannick Donnadieu ◽  
Delphine Tardif ◽  
Jean-Baptiste Ladant ◽  
Alexis Licht ◽  
...  
Keyword(s):  
Sea Level ◽  
Northern Hemisphere ◽  
Surface Albedo ◽  
Middle Eocene ◽  
Late Eocene ◽  
Strong Increase ◽  
High Latitudes ◽  
Sea Level Changes ◽  
Annual Range ◽  
Temperature Seasonality

<p>At the junction of warmhouse and coolhouse climate phases, the Eocene Oligocene Transition (EOT) is a key moment in the history of the Cenozoic climate. Yet, while it is accompanied by severe extinctions and biodiversity turnovers, terrestrial climate evolution remains poorly resolved. On lands, some fossil and geochemistry records suggest a particularly marked cooling in winter, which would have led to the development of more pronounced seasons (higher Mean Annual Range of Temperatures, MATR) in certain regions of the Northern Hemisphere. This type of climate change should have had consequences on biodiversity and an implication in some of the fauna and flora renewals described at the EOT. However, this season strengthening has been studied only superficially by model studies, and questions remain about the geographical extent of this phenomenon and the associated climatic processes. Although other components of the climate system vary seasonally (e.g., precipitation, wind), we therefore focus on the seasonality of temperatures only.</p><p>In order to better understand and describe temperature seasonality change patterns from the middle Eocene to the early Oligocene, we use the Earth System Model IPSL-CM5A2 and a set of simulations reconstructing the EOT through three major climate forcings: pCO2 decrease (1120/840 to 560 ppm), the Antarctic ice-sheet (AIS) formation, and the associated sea-level decrease (-70 m). </p><p>Our results suggest that seasonality changes across the EOT rely on the combined effects of the different tested mechanisms which result in zonal to regional climate responses. Sea-level changes associated with the earliest stage of the AIS formation may have also contributed to middle to late Eocene MATR reinforcement. We reconstruct strong and heterogeneous patterns of seasonality changes across the EOT. Broad continental areas of increased MATR reflect a strengthening of seasonality (from 4°C to > 10°C increase of the MATR) in agreement with MATR and Coldest Month Mean Temperatures (CMMT) changes indicated by a review of existing proxies. pCO2 decrease induces a zonal pattern with alternating increasing and decreasing seasonality bands. In the northern high-latitudes, it results in sea-ice and surface albedo feedback, driving a strong increase in seasonality (up to 8°C MATR increase). Conversely, the onset of the AIS is responsible for a more constant surface albedo, which leads to a strong decrease in seasonality in the southern mid- to high-latitudes (> 40°S). Finally, continental areas emerged due to the sea level lowering cause the largest increase in seasonality and explain most of the global heterogeneity in MATR changes patterns. The seasonality change patterns we reconstruct are consistent with the variability of the EOT biotic crisis intensity across the Northern Hemisphere.</p>

Mesocosm and Microcosm Experiments On the Feeding of Temperate Salt Marsh Foraminifera

2019 ◽  
Vol 49 (3) ◽  
pp. 259-274
Author(s):  
Jennifer L. Frail-Gauthier ◽  
Peta J. Mudie ◽  
Alastair G. B. Simpson ◽  
David B. Scott
Keyword(s):  
Salt Marsh ◽  
Sea Level ◽  
Environmental Changes ◽  
Eastern Canada ◽  
Form And Function ◽  
Transmission Electron ◽  
Salt Marsh Sediment ◽  
And Function ◽  
Key Indicators ◽  
Agglutinated Foraminifera

Abstract Agglutinated foraminifera dominate in temperate salt marsh sediment, making them key indicators for monitoring sea level and environmental changes. Little is known about the biology of these benthic foraminifera because of difficulties in distinguishing live from dead specimens in laboratory cultures. We present data from 10 years of laboratory experiments using comparisons of the agglutinant trochamminids Trochammina inflata and Entzia macrescens and the miliolid Miliammina fusca with the calcareous rotalids Helenina anderseni and Elphidium williamsoni. Specimens were taken from a laboratory mesocosm representing Chezzetcook Inlet, a cool-temperate salt marsh in eastern Canada. We determined culture requirements for the agglutinated foraminifera in Petri dishes over 10–12 week periods. Five inexpensive, non-terminal ways of identifying live organisms were developed: spatial movement, detritus-gathering, attachment, clustering, and test opacity. Comparison with rose Bengal staining showed <10% diversion for calcareous species and T. inflata but M. fusca was over-counted by >30%. Terminal chambers of Trochammina inflata were examined by transmission electron microscopy to visualise food consumption and identify food in digestive vacuoles, both in specimens from mesocosm and in culture. Bacteria and unidentified detritus in the vacuoles establish that this agglutinated species is a saprophagous and bacterivorous detritivore. The adhesive secretions by these species apparently help them gather and possibly farm food while being relatively immobile in the sediments. Our observations of movement and feeding orientation in the agglutinants suggest links between form and function that underscore their value as ultra high resolution sea-level proxies. Mesocosm biomass and abundance counts show that foraminifera represent >50% of the meiofaunal biomass, emphasising their importance in the food web and energy-flow dynamics of temperate salt marsh systems.

scholarly journals Revisiting extreme precipitation amounts over southern South America and implications for the Patagonian Icefields

2020 ◽  
Vol 24 (4) ◽  
pp. 2003-2016 ◽  
Author(s):  
Tobias Sauter
Keyword(s):  
Sea Level ◽  
Environmental Changes ◽  
Net Primary Production ◽  
Precipitation Amount ◽  
Moisture Flux ◽  
Polar Regions ◽  
Surface Mass ◽  
Precipitation Estimates ◽  
Modelling Studies ◽  
New Perspective

Abstract. Patagonia is thought to be one of the wettest regions on Earth, although available regional precipitation estimates vary considerably. This uncertainty complicates understanding and quantifying the observed environmental changes, such as glacier recession, biodiversity decline in fjord ecosystems and enhanced net primary production. The Patagonian Icefields, for example, are one of the largest contributors to sea-level rise outside the polar regions, and robust hydroclimatic projections are needed to understand and quantify current and future mass changes. The reported projections of precipitation from numerical modelling studies tend to overestimate those from in situ determinations, and the plausibility of these numbers has never been carefully scrutinized, despite the significance of this topic to our understanding of observed environmental changes. Here I use simple physical arguments and a linear model to test the plausibility of the current precipitation estimates and its impact on the Patagonian Icefields. The results show that environmental conditions required to sustain a mean precipitation amount exceeding 6.09±0.64 m yr−1 are untenable according to the regional moisture flux. The revised precipitation values imply a significant reduction in the surface mass balance of the Patagonian Icefields compared to previously reported values. This yields a new perspective on the response of Patagonia's glaciers to climate change and their sea-level contribution and might also help reduce uncertainties in the change of other precipitation-driven environmental phenomena.

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