IGA LECTURE!
Galway - Tuesday 29th October, 2013 Dublin - Tuesday 5th November, 2013
Dr. Dave Chew (TCD) will present a lecture:
Measuring time in Palaeozoic sedimentary sequences by geochronology
VENUE: Galway – University College Galway
Dublin - TBC
TIME: 6:30pm
Measuring time in Palaeozoic sedimentary sequences by geochronology
Abstract
Precise absolute age dating of sedimentary sequences is extremely important in establishing the timing and duration of many geological processes, including climatic fluctuations or rates of evolutionary change. This presentation will consist of two case studies from Carboniferous sequences in NW Europe (Ireland, England and Belgium). The first case study employs precise U-Pb TIMS zircon dating of Carboniferous volcanic layers. These volcanic layers are interbedded within sedimentary sequences which exhibit evidence for substantial sea level fluctuations. These sea level changes are attributed to the advance and retreat of the Gondwana ice cap which was situated over the South Pole in Carboniferous times. The geochronology data demonstrate that Milankovitch forcing (c. 100 ka cycles) was important during Carboniferous times. The second case study involves dating sedimentary rocks by two relatively new isotopic methods (Re-Os dating of black shales and U-Pb dating of diagenetic xenotime). These methods are applied to the same sequences dated by the U-Pb zircon method, and allow us to determine the suitability of the Re-Os black shale and U-Pb diagenetic xenotime chronometers to dating older, fossil-free sedimentary units.
Dr. Dave Chew
David Chew is a Lecturer in the Department of Geology in the School of Natural Sciences. David studied geology at University College Dublin, obtaining his B.Sc. in 1996 and his Ph.D. in 2001. He then took up a temporary lectureship in Trinity before moving to the University of Geneva in 2003 as a post-doctoral fellow. He returned to Trinity in late 2005 to take up a lectureship. His research interests involve applying state-of-the-art analytical techniques in geochronology and isotope geochemistry to various problems in the field of tectonics. This has included investigating the timing of deformation and metamorphism in orogenic belts (the Caledonides and the Andes), and the formation of continental rift zones such as the East African rift. He has also led two SFI-funded projects on isotopic dating of sedimentary rocks. He is currently applying these techniques to investigating the age and duration of ancient glacial deposits in the geological record.