Platform/Foreslope Facies and Buildup Geometry Resulting from Short-Term and Long-Term Eustatic Sea Level Fluctuations: Latemar Buildup (Middle Triassic), Dolomites, Northern Italy: ABSTRACT

AAPG Bulletin ◽  
1987 ◽  
Vol 71 ◽  
Author(s):  
Mark T. Harris, Robert Goldhammer
Keyword(s):  
Sea Level ◽  
Middle Triassic ◽  
Northern Italy ◽  
Short Term ◽  
Sea Level Fluctuations

scholarly journals An introduction to causes and consequences of Cretaceous sea-level changes (IGCP 609)

2019 ◽  
Vol 498 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Michael Wagreich ◽  
Benjamin Sames ◽  
Malcolm Hart ◽  
Ismail O. Yilmaz
Keyword(s):  
Sea Level ◽  
Sea Level Changes ◽  
Short Term ◽  
Sea Level Fluctuations ◽  
Groundwater Aquifer ◽  
Sea Level Oscillations ◽  
Short And Long Term ◽  
Geological Timescale ◽  
Land Water

AbstractThe International Geoscience Programme Project IGCP 609 addressed correlation, causes and consequences of short-term sea-level fluctuations during the Cretaceous. Processes causing several ka to several Ma (third- to fourth-order) sea-level oscillations during the Cretaceous are so far poorly understood. IGCP 609 proved the existence of sea-level cycles during potential ice sheet-free greenhouse to hothouse climate phases. These sea-level fluctuations were most probably controlled by aquifer-eustasy that is altering land-water storage owing to groundwater aquifer charge and discharge. The project investigated Cretaceous sea-level cycles in detail in order to differentiate and quantify both short- and long-term records based on orbital cyclicity. High-resolution sea-level records were correlated to the geological timescale resulting in a hierarchy of sea-level cycles in the longer Milankovitch band, especially in the 100 ka, 405 ka, 1.2 Ma and 2.4 Ma range. The relation of sea-level highs and lows to palaeoclimate events, palaeoenvironments and biota was also investigated using multiproxy studies. For a hothouse Earth such as the mid-Cretaceous, humid–arid climate cycles controlling groundwater-related sea-level change were evidenced by stable isotope data, correlation to continental lake-level records and humid–arid weathering cycles.

scholarly journals Reconstruction of Caspian Sea-Level Fluctuations: Radiocarbon Dating Coastal and Bottom Deposits

Radiocarbon ◽  
1993 ◽  
Vol 35 (3) ◽  
pp. 409-420 ◽  
Author(s):  
Yu. A. Karpytchev
Keyword(s):  
Sea Level ◽  
Salt Marshes ◽  
Caspian Sea ◽  
Climatic Changes ◽  
Short Term ◽  
The Caspian Sea ◽  
Sea Level Fluctuations ◽  
The Impact ◽  
Basin Area

Owing to the large basin area of the Caspian Sea, fluctuations in its level reflect climatic changes in the northern hemisphere. To reconstruct these fluctuations, I collected mollusk shells, plant debris, carbonates and organic matter samples for 14C dating from deposits of ancient salt marshes, depressions and bars formed during significant sea-level decline. I studied the impact of eolian sedimentation via parallel dating of carbonates and other materials. The data demonstrate that sea level rises during periods of cooling and falls during warming periods; this is true for both long-term (2–2.5 ka) and short-term climatic changes.

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.

Revising key parameters for long-term carbon cycle models

2021 ◽  
Author(s):  
Chloé M. Marcilly ◽  
Trond H. Torsvik ◽  
Mathew Domeier ◽  
Dana L. Royer
Keyword(s):  
Sea Level ◽  
Age Distribution ◽  
Silicate Weathering ◽  
Geological Time ◽  
Sea Levels ◽  
Climate Fluctuations ◽  
Climate Gradients ◽  
Sea Level Fluctuations ◽  
Temperature And Precipitation

<p>CO<sub>2</sub> is the most important greenhouse gas in the Earth’s atmosphere and has fluctuated considerably over geological time. However, proxies for past CO<sub>2 </sub>concentrations have large uncertainties and are mostly limited to Devonian and younger times. Consequently, CO<sub>2</sub> modelling plays a key role in reconstructing past climate fluctuations. Facing the limitations with the current CO<sub>2</sub> models, we aim to refine two important forcings for CO<sub>2</sub> levels over the Phanerozoic, namely carbon degassing and silicate weathering.</p><p>Silicate weathering and carbonate deposition is widely recognized as a primary sink of carbon on geological timescales and is largely influenced by changes in climate, which in turn is linked to changes in paleogeography. The role of paleogeography on silicate weathering fluxes has been the focus of several studies in recent years. Their aims were mostly to constrain climatic parameters such as temperature and precipitation affecting weathering rates through time. However, constraining the availability of exposed land is crucial in assessing the theoretical amount of weathering on geological time scales. Associated with changes in climatic zones, the fluctuation of sea-level is critical for defining the amount of land exposed to weathering. The current reconstructions used in<sub></sub>models tend to overestimate the amount of exposed land to weathering at periods with high sea levels. Through the construction of continental flooding maps, we constrain the effective land area undergoing silicate weathering for the past 520 million years. Our maps not only reflect sea-level fluctuations but also contain climate-sensitive indicators such as coal (since the Early Devonian) and evaporites to evaluate climate gradients and potential weatherablity through time. This is particularly important after the Pangea supercontinent formed but also for some time after its break-up.</p><p>Whilst silicate weathering is an important CO<sub>2</sub> sink, volcanic carbon degassing is a major source but one of the least constrained climate forcing parameters. There is no clear consensus on the history of degassing through geological time as there are no direct proxies for reconstructing carbon degassing, but various proxy methods have been postulated. We propose new estimates of plate tectonic degassing for the Phanerozoic using both subduction flux from full-plate models and zircon age distribution from arcs (arc-activity) as proxies.</p><p>The effect of revised modelling parameters for weathering and degassing was tested in the well-known long-term models GEOCARBSULF and COPSE. They revealed the high influence of degassing on CO<sub>2</sub> levels using those models, highlighting the need for enhanced research in this direction. The use of arc-activity as a proxy for carbon degassing leads to interesting responses in the Mesozoic and brings model estimates closer to CO<sub>2 </sub> proxy values. However, from simulations using simultaneously the revised input parameters (i.e weathering and degassing) large model-proxy discrepancies remain and notably for the Triassic and Jurassic.</p><p> </p>

scholarly journals Aquifer-eustasy as the main driver of short-term sea-level fluctuations during Cretaceous hothouse climate phases

2019 ◽  
Vol 498 (1) ◽  
pp. 9-38 ◽  
Author(s):  
Benjamin Sames ◽  
M. Wagreich ◽  
C. P. Conrad ◽  
S. Iqbal
Keyword(s):  
Sea Level ◽  
Phase Relationship ◽  
Sea Level Changes ◽  
Short Term ◽  
Groundwater Levels ◽  
Sequence Stratigraphic ◽  
Sea Level Fluctuations ◽  
Minimum Estimate ◽  
Underlying Mechanisms ◽  
Continental Ice Sheets

AbstractA review of short-term (<3 myr: c. 100 kyr to 2.4 myr) Cretaceous sea-level fluctuations of several tens of metres indicates recent fundamental progress in understanding the underlying mechanisms for eustasy, both in timing and in correlation. Cretaceous third- and fourth-order hothouse sea-level changes, the sequence-stratigraphic framework, are linked to Milankovitch-type climate cycles, especially the longer-period sequence-building bands of 405 kyr and 1.2 myr. In the absence of continental ice sheets during Cretaceous hothouse phases (e.g. Cenomanian–Turonian), growing evidence indicates groundwater-related sea-level cycles: (1) the existence of Milankovitch-type humid-arid climate oscillations, proven via intense humid weathering records during times of regression and sea-level lowstands; (2) missing or inverse relationships of sea-level and the marine δ18O archives, i.e. the lack of a pronounced positive excursion, cooling signal during sea-level lowstands; and (3) the anti-phase relationship of sea and lake levels, attesting to high groundwater levels and charged continental aquifers during sea-level lowstands. This substantiates the aquifer-eustasy hypothesis. Rates of aquifer-eustatic sea-level change remain hard to decipher; however, reconstructions range from a very conservative minimum estimate of 0.04 mm a−1 (longer time intervals) to 0.7 mm a−1 (shorter, probably asymmetric cycles). Remarkably, aquifer-eustasy is recognized as a significant component for the Anthropocene sea-level budget.

Ample and recurrent sea-level fluctuations during the Bajocian: A hint towards middle Jurassic glacio-eustatism

2020 ◽  
Author(s):  
Stéphane Bodin ◽  
Jan Danisch ◽  
Malte Mau ◽  
Francois-Nicolas Krencker ◽  
Alexis Nutz ◽  
...  
Keyword(s):  
Sea Level ◽  
Middle Jurassic ◽  
Sediment Supply ◽  
Medium Term ◽  
High Atlas ◽  
Sea Level Fluctuations ◽  
R Packages ◽  
Central High ◽  
Central High Atlas

&lt;p&gt;&lt;span&gt;Mesozoic sea-level fluctuations have been a matter of debate for several decades, especially the extend and origin of sea-level cycles that have a periodicity of about 1 Myr or less. The debate lies in the main driving mechanism for sequence development (global sea-level or sediment flux variations) as well as the reason behind water exchanges between the continents and the oceans (glacio- or aquifer-eustatism). In this study, we focus on the carbonate-dominated sedimentary record of the Bajocian (Middle Jurassic) in the Central High Atlas Basin of Morocco. Several aspects make this basin an appropriate location for discussing Middle Jurassic sea-level changes. Firstly, the outstanding exposures of the High Atlas Mountains, with continuous exposures for 10s of kilometres, allow to describe and track sedimentary packages and their bounding surfaces from proximal to distal settings. Moreover, a combination of ammonite and brachiopod biostratigraphy with carbon-isotopes chemostratigraphy allows to temporarily constrain their development, which permits to correlate and compare the Central High Atlas sedimentary record to other basins. Finally, due to high-subsidence rates, thick Bajocian sedimentary sequences have accumulated, minimizing condensation and hiatus that might prevail in other basins due to a lack of accommodation space creation. Two Bajocian long-term transgressive-regressive (T-R) packages are observed throughout the basin. They are modulated by several medium-term T-R packages, that have each an approximate duration of 1 Myr. These sequences can also be correlated on a basinwide scale. Combined with sedimentological and facies analyses, architectural evidence along proximal-to-distal transect illustrates that several of the medium-term sequences are characterized by the presence of a falling stage and lowstand systems tracts, demonstrating that medium-term T-R stacking patterns are not solely linked to fluctuation in sediment supply, but also to episodes of relative sea-level fall of at least 30m of amplitude. This is confirmed by backstripping analysis performed in a composite section from the center of the Basin. Comparison with Bajocian deposits from France and Scotland, where good biostratigraphic dating is also available, shows that similar contemporaneous sea-level fall can be observed, highlighting their potential global character. The two long-term Bajocian sequences are more difficult to correlate on a global scale, suggesting that they are rather primarily linked to fluctuation in regional sediment supply or dynamic topography processes. The exact cause of the Bajocian medium-term sea-level falls is currently unknown, but it is here interesting to note that a relatively cool globate climate has been postulated for the Middle Jurassic, suggesting that glacio-eustasy was their most likely driver.&lt;/span&gt;&lt;/p&gt;

scholarly journals Forecasting sea level fluctuations caused by storm winds at the ports in Odesa Region of the north-western part of the Black Sea

2020 ◽  
pp. 105-114
Author(s):  
Yu. S. Tuchkovenko ◽  
O. S. Matygin ◽  
V. Yu. Chepurna
Keyword(s):  
Sea Level ◽  
Black Sea ◽  
Lead Time ◽  
The Black Sea ◽  
Short Term ◽  
Sea Level Fluctuations ◽  
The North ◽  
Operational Forecasting ◽  
Forecast Lead Time ◽  
North Western

Increasing the draught of ships that may be accepted by ports for loading at their loading berths is one of the main tasks aimed at development and freight turnover enhancement of sea trade ports located in Odesa Region of the north-western part of the Black Sea (cities of Chornomorsk, Odesa and Pivdennyi). An operational forecasting of short-term sea level fluctuations caused by storm winds presents a critical task for ensuring safe navigation across the ports’ water area and approach channels. The article is devoted to analysing and discussing the results of tests of a simplified 2D hydrodynamic model designed for forecasting such phenomena as upsurge and downsurge of the sea level caused by storm winds in the vicinity of sea ports in Odesa Region of the north-western part of the Black Sea. Spatio-temporal variability of wind conditions at the sea-to-atmosphere boundary was set based on the data retrieved from a 10-day synoptic forecast using global atmospheric prediction model GFS (Global Forecast System). The study analyses the results of forecast of significant (the ones exceeding 30 cm) short-term sea level drops and rises at the ports which were observed in 2016, 2017 and 2020. It was established that, in case of use of the GFS forecast data, the pattern of sea level denivellations caused by storm winds and their amplitude in the majority of events start approximating to the observed values provided the forecast has a 4-day lead time. Therefore the accuracy of wind conditions variability forecast with application of the GFS model having a longer lead advance time is not sufficient for forecasting the sea level fluctuations caused by storm winds.  The study made it possible to get an acceptable equivalence between the values of sea level denivellation amplitudes which were forecast with a 1-to-3-day lead time and the ones observed afterwards. In particular, when the forecast lead time is equal to »2 days, in relation to the expected storm conditions, the average absolute error for the forecast of sea level fluctuations amplitude constituted 7-8 cm, while its permissible value was defined as 15 cm, and the average relative error – 16-18%. It allowed making a conclusion that a hydrodynamic model option, applied alongside with the forecasting information on wind conditions variability retrieved with the help of the GFS weather prediction model, may be used for operational forecasting of short-term sea level fluctuations caused by storm winds with the forecast lead time of up to 4 days.

scholarly journals Short-Term Sea Level Changes of the Upper Cretaceous Carbonates: Calibration between Palynomorphs Composition, Inorganic Geochemistry, and Stable Isotopes

Minerals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1099
Author(s):  
Ahmed Mansour ◽  
Thomas Gentzis ◽  
Michael Wagreich ◽  
Sameh S. Tahoun ◽  
Ashraf M.T. Elewa
Keyword(s):  
Sea Level ◽  
Late Cretaceous ◽  
Upper Cretaceous ◽  
Freshwater Algae ◽  
Sea Level Changes ◽  
Short Term ◽  
Sea Level Oscillations ◽  
Rising Sea Level ◽  
Southern Tethys

Widespread deposition of pelagic-hemipelagic sediments provide an archive for the Late Cretaceous greenhouse that triggered sea level oscillations. Global distribution of dinoflagellate cysts (dinocysts) exhibited a comparable pattern to the eustatic sea level, and thus, considered reliable indicators for sea level and sequence stratigraphic reconstructions. Highly diverse assemblage of marine palynomorphs along with elemental proxies that relate to carbonates and siliciclastics and bulk carbonate δ13C and δ18O from the Upper Cretaceous Abu Roash A Member were used to reconstruct short-term sea level oscillations in the Abu Gharadig Basin, southern Tethys. Additionally, we investigated the relationship between various palynological, elemental, and isotope geochemistry parameters and their response to sea level changes and examined the link between these sea level changes and Late Cretaceous climate. This multiproxy approach revealed that a long-term sea-level rise, interrupted by minor short-term fall, was prevalent during the Coniacian-earliest Campanian in the southern Tethys, which allowed to divide the studied succession into four complete and two incomplete 3rd order transgressive-regressive sequences. Carbon and oxygen isotopes of bulk hemipelagic carbonates were calibrated with gonyaulacoids and freshwater algae (FWA)-pteridophyte spores and results showed that positive δ13Ccarb trends were consistent, in part, with excess gonyaulacoid dinocysts and reduced FWA-spores, reinforcing a rising sea level and vice versa. A reverse pattern was shown between the δ18Ocarb and gonyaulacoid dinocysts, where negative δ18Ocarb trends were slightly consistent with enhanced gonyaulacoid content, indicating a rising sea level and vice versa. However, stable isotope trends were not in agreement with palynological calibrations at some intervals. Therefore, the isotope records can be used as reliable indicators for reconstructing changes in long-term sea level rather than short-term oscillations.

Carbohydrate Metabolism in Fed and Fasted Rats Exposed to an Altitude of 12,470 Feet

1958 ◽  
Vol 193 (2) ◽  
pp. 415-424 ◽  
Author(s):  
Paola S. Timiras ◽  
Robert Hill ◽  
Alvin A. Krum ◽  
Adam W. Lis
Keyword(s):  
Sea Level ◽  
Heart Muscle ◽  
Glycogen Content ◽  
Level Control ◽  
Short Term ◽  
Filial Generation ◽  
Sugar Levels ◽  
And Control ◽  
Fasted Rats

Blood sugar levels and the glycogen content of liver, heart, skeletal muscle, diaphragm and kidney of both fed and fasted sea level control rats were compared with those of fed and fasted rats (P) born at sea level and then exposed to an altitude of 12,470 feet for various periods of time, and with those of fed rats (F2) of the second filial generation born and maintained at altitude. In the P animals after short-term (24 and 72 hr.) exposure, liver, heart, muscle and diaphragm glycogen was markedly decreased in the fed animals as compared with the fed sea level controls, and markedly increased in the fasted hypoxic animals as compared with the fasted sea level controls. In fed P animals after long-term exposure, liver, heart, muscle and diaphragm glycogen was the same as in fed controls after 2 and 6 months at altitude, and became markedly lower than in the controls after 10 months. In the F2 rats, liver and muscle glycogen was markedly decreased when compared with the controls; in contrast, cardiac glycogen content was significantly higher in these F2 rats than in the controls. Changes were not observed in kidney glycogen. Hyperglycemia was observed in all P rats after 24 hours, and hypoglycemia after 72 hours at altitude. In the long-term experiments glycemia was the same in experimental (P and F2) and control rats.

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