Detrital zircon dating define antedating


08-Aug-2017 09:56

Through U–Pb dating of detrital zircons collected from six conglomerate samples from the dinosaur bone beds, we found that the youngest single grain age (YSG) of sample 090414-24-D was 77.3 Ma, representing the maximum depositional age of the dinosaur fossil beds and sediments.This also indicates that the Hongtuya Formation was deposited during the Campanian.► Detrital zircon U–Pb dating reveals younger depositional ages for the graywackes.► The Armantai ophiolite was emplaced prior to the Early Devonian.The mass burial of dinosaur bone fossils in the Late Cretaceous Wangshi Group in Zhucheng, Shandong Province has been a research focus in recent years.However, the provenance of the dinosaur bone fossils and the accurate depositional age of the bone beds remain ambiguous.

The results show that short-term rates for the Himalayas, which range from 0.70 ± 0.09 to 2.67 ± 0.40 km/Myr and average 1.75 ± 0.59 (1 ) km/Myr.

A U-Pb-He double-dating method is applied to detrital zircons with core-rim structure from the Ganges River in order to determine average short- and long-term exhumation rates for the Himalayas.

Long-term rates are calculated from the U/Pb ages of metamorphic rims of the grains that formed during the Himalayan orogeny and their crystallization temperatures, which are calculated from the Ti-in-zircon thermometer.

The differences between the long-term and short-term rates can be attributed to continuous exhumation of the host rocks in different mechanisms in continental collision orogen.

The U/Pb ages of 44.0 ± 3.7 to 18.3 ± 0.5 Ma for the zircon rims indicate a protracted episode of ∼25 Myr for regional metamorphism of the host rocks at deeper crust, whereas the (U-Th)/He ages of 42.2 ± 1.8 to 1.3 ± 0.2 Ma for the zircon grains represent a protracted period of ∼40 Myr for exposure of the host rocks to shallower crustal level.Dating results revealed an age peak of 120–110 Ma, which corresponds with the peak age of volcanic rocks of the Lower Cretaceous Qingshan Group.



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