A new calibration curve for the conversion of radiocarbon ages to calibrated (cal) ages has been constructed and internationally ratified to replace IntCal98, which extended from 0–24 cal kyr BP ...(Before Present, 0 cal BP = AD 1950). The new calibration data set for terrestrial samples extends from 0–26 cal kyr BP, but with much higher resolution beyond 11.4 cal kyr BP than IntCal98. Dendrochronologically-dated tree-ring samples cover the period from 0–12.4 cal kyr BP. Beyond the end of the tree rings, data from marine records (corals and foraminifera) are converted to the atmospheric equivalent with a site-specific marine reservoir correction to provide terrestrial calibration from 12.4–26.0 cal kyr BP. A substantial enhancement relative to IntCal98 is the introduction of a coherent statistical approach based on a random walk model, which takes into account the uncertainty in both the calendar age and the 14C age to calculate the underlying calibration curve. The tree-ring data sets, sources of uncertainty, and regional offsets are discussed here. The marine data sets and calibration curve for marine samples from the surface mixed layer (Marine04) are discussed in brief, but details are presented elsewhere. We do not make a recommendation for calibration beyond 26 cal kyr BP at this time; however, potential calibration data sets are compared in another paper.
Annually laminated (varved) sediments are a valuable resource for studies of global climate change. High-resolution paleoclimate records show that the climate system is capable of changing rapidly. ...Well-dated records are crucial to determining the relative timing of events in distant locations, and therefore to identifying lead-lag relationships and possible forcing mechanisms of abrupt climate changes. In this thesis, well-dated high-resolution records are produced from varved sediments in two disparate environments-tidewater lakes on southern Baffin Island in the eastern Canadian Arctic, and the tropical marine Cariaco Basin off the coast of Venezuela. For these studies, multiple, independent dating techniques are used to demonstrate that paired-laminae couplets are annually deposited varves. In addition to providing annual chronologies for other paleoenvironmental proxy records, varved sediments themselves are sensitive recorders of paleoclimate. For example, dark laminae thickness from Upper Soper Lake, measured independently from light laminae, is shown to correspond to average June temperature, and used to create a record of paleotemperature variability on southern Baffin Island for the last 500 years. Annually resolved light laminae thickness and relative reflectance (grey scale) records from the Cariaco Basin show the same patterns, timing, and rates of change during the last deglaciation as records from Greenland ice cores. These records show close agreement at time scales of decades to millennia, providing evidence for strong linkages between climate systems of the high and low latitude North Atlantic regions. Cariaco Basin varves are also applicable to studies involving radiocarbon variability. A 5500 year-long floating varve chronology was constructed and anchored to absolute calendar time. The resulting data set extends high-resolution $\sp{14}$C calibration 3000 years prior to the tree ring calibration, and resolves century-scale features not seen in coral U/Th data sets. The Cariaco Basin data also provide a record of past atmospheric radiocarbon concentration, or $\Delta\sp{14}$C. Paleoclimate and $\Delta\sp{14}$C records from the same core, together with geochemical box model experiments, provide insight into ocean circulation changes during the Younger Dryas cold event. At that time, North Atlantic Deep Water formation ceased and was gradually replaced by ocean ventilation elsewhere, possibly by the formation of North Atlantic Intermediate Water.
The American Association of Petroleum Geologists (AAPG) announced in February that the group had given novelist Michael Crichton its 2006 Journalism Award for his novels Jurassic Park and State of ...Fear. AAPG states that the Journalism Award is intended to acknowledge those who have contributed to the public understanding of geology.
The Council of the American Quaternary Association (AMQUA),a professional organization of scientists who study the recent (Quaternary) period of geologic time in which mankind has flourished, feels it was inappropriate for AAPG to give a journalism award for State of Fear for two reasons. The novel is not journalism. Furthermore, it is fiction that presents a distorted view of global warming as a scientific hoax, and Crichton is using his prominence as a novelist and movie director to push his views into the scientific debate on global warming and its consequences.
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