Geological timescale | ScienceGate

During the late Miocene, meridional sea surface temperature gradients, deep ocean circulation patterns, and continental configurations evolved to a state similar to modern day. Deep-sea benthic foraminiferal stable oxygen (&#948;18O) and carbon (&#948;13C) isotope stratigraphy remains a fundamental tool for providing accurate chronologies and global correlations, both of which can be used to assess late Miocene climate dynamics. Until recently, late Miocene benthic &#948;18O and &#948;13C stratigraphies remained poorly constrained, due to relatively poor global high-resolution data coverage.Here, I present ongoing work that uses high-resolution deep-sea foraminiferal stable isotope records to improve late Miocene (chrono)stratigraphy. Although challenges remain, the coverage of late Miocene benthic &#948;18O and &#948;13C stratigraphies has drastically improved in recent years, with high-resolution records now available across the Atlantic and Pacific Oceans. The recovery of these deep-sea records, including the first astronomically tuned, deep-sea integrated magneto-chemostratigraphy, has also helped to improve the late Miocene geological timescale. Finally, I will briefly touch upon how our understanding of late Miocene climate evolution has improved, based on the high-resolution deep-sea archives that are now available.

Download Full-text

DO PERIODICITIES IN EXTINCTION—WITH POSSIBLE ASTRONOMICAL CONNECTIONS—SURVIVE A REVISION OF THE GEOLOGICAL TIMESCALE?

The Astrophysical Journal ◽

10.1088/0004-637x/773/1/6 ◽

2013 ◽

Vol 773 (1) ◽

pp. 6 ◽

Cited By ~ 17

Author(s):

Adrian L. Melott ◽

Richard K. Bambach

Keyword(s):

Geological Timescale

Download Full-text

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

Geological Society London Special Publications ◽

10.1144/sp498-2019-156 ◽

2019 ◽

Vol 498 (1) ◽

pp. 1-8 ◽

Cited By ~ 2

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.

Download Full-text

The CA-IDTIMS Method and the Calibration of Endemic Australian Palynostratigraphy to the Geological Timescale

10.1190/ice2015-2210718 ◽

2015 ◽

Cited By ~ 1

Author(s):

John R. Laurie* ◽

Simon Bodorkos ◽

Tegan E. Smith ◽

Jim Crowley ◽

Robert S. Nicoll

Keyword(s):

Geological Timescale

Download Full-text

Astronomical calibration of the geological timescale: closing the middle Eocene gap

Climate of the Past Discussions ◽

10.5194/cpd-11-1665-2015 ◽

2015 ◽

Vol 11 (3) ◽

pp. 1665-1699 ◽

Cited By ~ 3

Author(s):

T. Westerhold ◽

U. Röhl ◽

T. Frederichs ◽

S. M. Bohaty ◽

J. C. Zachos

Keyword(s):

Time Scale ◽

Middle Eocene ◽

Age Dating ◽

Geological Time ◽

Geological Time Scale ◽

Sedimentary Sequences ◽

Climate Reconstructions ◽

Thermal Maximum ◽

Astronomical Time ◽

Geological Timescale

Abstract. To explore cause and consequences in past climate reconstructions highly accuracy age models are inevitable. The highly accurate astronomical calibration of the geological time scale beyond 40 million years critically depends on the accuracy of orbital models and radio-isotopic dating techniques. Discrepancies in the age dating of sedimentary successions and the lack of suitable records spanning the middle Eocene have prevented development of a continuous astronomically calibrated geological timescale for the entire Cenozoic Era. We now solve this problem by constructing an independent astrochronological stratigraphy based on Earth's stable 405 kyr eccentricity cycle between 41 and 48 million years ago (Ma) with new data from deep-sea sedimentary sequences in the South Atlantic Ocean. This new link completes the Paleogene astronomical time scale and confirms the intercalibration of radio-isotopic and astronomical dating methods back through the Paleocene-Eocene Thermal Maximum (PETM, 55.930 Ma) and the Cretaceous/Paleogene boundary (66.022 Ma). Coupling of the Paleogene 405 kyr cyclostratigraphic frameworks across the middle Eocene further paves the way for extending the Astronomical Time Scale (ATS) into the Mesozoic.

Download Full-text

Prosets: making continued use of fossil fuels compatible with a credible transition to net zero

10.21203/rs.3.rs-240578/v1 ◽

2021 ◽

Author(s):

Eli Mitchell-Larson ◽

Myles Allen

Keyword(s):

Fossil Fuels ◽

Clear Definition ◽

Carbon Offsetting ◽

Net Zero ◽

Continued Use ◽

New Form ◽

Near Term ◽

Definition Of ◽

Geological Timescale

Abstract Interest in carbon offsetting is resurging among companies and institutions, but existing offerings fail to make continued use of fossil fuels compatible with a credible transition to sustainable net zero emissions. A clear definition of what makes an offset net-zero-compliant is needed. We introduce the ‘proset’, a new form of composite offset in which the fraction of carbon allocated to geological-timescale storage options increases progressively, reaching 100% by the target net zero date, generating predictable demand for effectively permanent CO2 storage while making the most of the near-term opportunities provided by nature-based climate solutions, all at an affordable cost to the offset purchaser.

Download Full-text

Patterns of family extinction depend on definition and geological timescale

Deep Sea Research Part B Oceanographic Literature Review ◽

10.1016/0198-0254(85)94094-4 ◽

1985 ◽

Vol 32 (12) ◽

pp. 1059

Keyword(s):

Geological Timescale

Download Full-text

Customising the geological timescale for use in Australasia

The APPEA Journal ◽

10.1071/aj08019 ◽

2009 ◽

Vol 49 (1) ◽

pp. 301

Author(s):

John R Laurie ◽

Daniel Mantle ◽

Robert S Nicoll ◽

James Ogg

Keyword(s):

Sea Level ◽

Northern Hemisphere ◽

Time Scale ◽

Software Package ◽

Lookup Table ◽

International Commission ◽

Extensive Literature ◽

Literature Searches ◽

Geological Timescale ◽

The Web

The global standard geological timescale (GTS 2004) is largely built around northern hemisphere datasets. Consequently, a large proportion of the biozones used in Australia were not included, thus hampering its implementation in the region. Previously, most of the Australasian biozonal schemes had been tied to the Australian Geological Survey Organisation timescale (AGSO 1996) but each of these needed to be recalibrated to tie with the updated and globally standardised GTS 2004. This process was complicated by the fact that several of the local biozonal schemes have been revised in the intervening period. The updates of Australian biozones to GTS 2004 compliance were accomplished using extensive literature searches as well as targetted reviews of some biozonal schemes. These recalibrated and amended schemes have now been included in Geoscience Australia’s Timescales Database, which acts as a core lookup table for numerous databases across the organisation. In 2010, GTS 2004 will be replaced by an updated standard timescale. To facilitate this transition and other future revisions, Geoscience Australia’s Timescales Database is being revised to store the relationships between biozones and the geological timescale in a format that will allow essentially automatic, rather than protracted manual, updates. A public visualisation software package, Time Scale Creator, is available on the web from the International Commission on Stratigraphy (ICS) to display user-selected intervals from an ICS database suite of over 20,000 biological, geomagnetic, sea-level, and other events with ages consistent with GTS 2004. Geoscience Australia (GA) has compiled a customised datapack for Time Scale Creator which includes most Australian biozonal schemes. In addition, Geoscience Australia is using the lithostratigraphic capabilities of this software package to generate basin biozonation and stratigraphy charts, which supersede those published nearly a decade ago.

Download Full-text

Dynamical mechanism of the poleward intensification of the Southern Hemispheric Westerlies due to sea ice extent change

10.5194/egusphere-egu2020-15627 ◽

2020 ◽

Author(s):

Hyeong-Gyu Kim ◽

Joowan Kim ◽

Sang-Yoon Jun ◽

Seong-Joong Kim

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Ocean Circulation ◽

Atmospheric Temperature ◽

Sea Ice Extent ◽

Dynamical Mechanism ◽

Antarctic Sea Ice ◽

Crucial Component ◽

Ice Conditions ◽

Geological Timescale

Paleoclimate data shows a good correlation between the concentration of CO2 and atmospheric temperature in the geological timescale. Many studies compare the Last Glacial Maximum (LGM) and the Pre-Industrial era (PI), to understand the coupling processes. A popular mechanism explaining this coupling process is a modulation of the ocean circulation and related CO2 emission over the Southern Ocean due to atmospheric westerly. The atmospheric westerly plays an important role in driving ocean circulation; however, the related processes are not fully understood for the LGM period.In this study, we examine physical processes determining the characteristics of the atmospheric westerly focusing on the Southern Ocean. Atmospheric states for LGM and PI are reproduced using a coupled earth system model with different sea ice conditions. A poleward intensification of the Southern Hemispheric Westerlies is observed for the LGM experiment. A comparison to PI shows that the meridional temperature gradient largely determines this intensification, and the enhanced meridional gradient is observed due to decreased heat flux from the subantarctic ocean in the LGM experiment. This result suggests that the Antarctic sea ice is a crucial component for understanding the Southern Hemispheric Westerly.

Download Full-text