CCT1 - Rationale and Goals


Rationale

Accurate chronologies of paleoenvironment and paleoclimate records are necessary in many aspects of paleoscience. First, detailed comparisons between different land, ocean and ice archives requires that records are brought onto a common absolute or relative timescale that resolves (at least) the timescale of interest. Second, meaningful comparison of paleoenvironmental datasets from different locations with modeling results requires high- resolution and accurate dating.

CCT1-chrono-Fig2.19
Late Quaternary depositional environments (ice caps, glacial moraine deposits, loess and sand dunes, trees, marine sediments, speleothems, lake sediments) and associated dating techniques. The lower part of the figure represents the effective dating ranges of the different techniques (Figure by S. Bertrand).

Finally, a growing interest in Earth System variability on centennial, decadal and interannual timescales, and in abrupt changes requires that the quality of chronological tools for paleoresearch keep pace with this demand.

The age model of paleorecords can be derived from a set of absolute (e.g. radiometric or layer counting) dates, or from the stratigraphic comparison with a well dated master record using (1) events not directly linked to climate (i.e. volcanic ashes, pollution peak, paleomagnetic variations) or (2) using climatic events detected in the proxy records (e.g. event stratigraphy). The major events of climate change are globally teleconnected but with leads and lags between regions, and in the environmental response. Therefore, any common master chronology that contains age references for these events needs to include the complexity of Earth System dynamics while at the same time providing satisfactory reliability.

PAGES strongly supports the numerous national and international projects, groups and commissions already working on solutions to the above issues and recognizes a need to integrate the different efforts.


Goals

Improve absolute dating:

Reduce the uncertainty of existing radiometric dating methods.

Improve calibration techniques, particularly for 14C calibration curves using tree rings, sediment varves, etc.

Develop new dating methods, e.g. for the time beyond the range of U/Th dating (before ~300 ka).

Improve chronostratigraphic dating:

Synthesize correlations of regionally occurring well-dated tephra on land and in the ocean with the ice core record.

Compile paleomagnetic master curves for all parts of the globe, including their millennial-scale variations.

Improve event stratigraphy:

Establish regional event stratigraphy master curves such as the NGRIP ice core.

Develop, as an update of the SPECMAP reference curves, a global network of high-resolution climate records from different regions and archives, with their time scales consistent between the records and relative to orbital solar insolation over at least the Mid-and Late Pleistocene.

Establish a high-resolution master curve of past global mean sea level change and spatial synopses of local changes.

The ultimate goal was to establish a set of regional master curves that are accurately dated with high-resolution age models that cover the Holocene, the Last glacial cycle, and the mid and late Pleistocene. These master curves should ideally be of annual resolution wherever possible, contain a good paleomagnetic and tephra record, and be sensitive to climate variations to enable event stratigraphic correlations.