• Publications
  • Influence
Intercalibration of standards, absolute ages and uncertainties in 40Ar/39Ar dating
The 40Ar/39Ar dating method depends on accurate intercalibration between samples, neutron fluence monitors, and primary 40Ar/40K (or other external) standards. The 40Ar/39Ar age equation may beExpand
Synchronizing Rock Clocks of Earth History
This calibration of tephras in marine deposits in Morocco to calibrate the age of Fish Canyon sanidine provides tight constraints for the astronomical tuning of pre-Neogene successions, resulting in a mutually consistent age of ∼65.95 Ma for the Cretaceous/Tertiary boundary. Expand
Joint determination of 40K decay constants and 40Ar∗/40K for the Fish Canyon sanidine standard, and improved accuracy for 40Ar/39Ar geochronology
Abstract 40Ar/39Ar and K–Ar geochronology have long suffered from large systematic errors arising from imprecise K and Ar isotopic data for standards and imprecisely determined decay constants forExpand
A test for systematic errors in 40Ar/39Ar geochronology through comparison with U/Pb analysis of a 1.1-Ga rhyolite
Important sources of systematic error in 40Ar/39Ar dating arise from uncertainties in the 40K decay constants and K/Ar isotopic data for neutron fluence monitors (standards). The activity dataExpand
2.5-million-year-old stone tools from Gona, Ethiopia
The artefacts show surprisingly sophisticated control of stone fracture mechanics, equivalent to much younger Oldowan assemblages of Early Pleistocene age, which indicates an unexpectedly long period of technological stasis in the Oldowan. Expand
Age and Timing of the Permian Mass Extinctions: U/Pb Dating of Closed-System Zircons
Zircons from nine ash beds within the Shangsi and Meishan sections (China), pretreated by annealing followed by partial attack with hydrofluoric acid, result in suites of consistent and concordant uranium/lead (U/Pb) ages, eliminating the effects of lead loss. Expand
Environment and behavior of 2.5-million-year-old Bouri hominids.
The combined evidence suggests that behavioral changes associated with lithic technology and enhanced carnivory may have been coincident with the emergence of the Homo clade from Australopithecus afarensis in eastern Africa. Expand
2.6-Million-year-old stone tools and associated bones from OGS-6 and OGS-7, Gona, Afar, Ethiopia.
This poster presents a meta-anatomy of the determinants of infectious disease in response to the infectious disease coronavirus, which killed more than 20,000 people around the world between 1991 and 2002. Expand
On the ages of flood basalt events
Abstract We review available data constraining the extent, volume, age and duration of all major Phanerozoic continental flood basalts (CFB or traps) and oceanic plateaus (OP), together forming theExpand