DSpace Collection:
https://hdl.handle.net/2440/13593
2024-03-28T15:32:34ZCambrian Sauk transgression in the Grand Canyon region redefined by detrital zircons
https://hdl.handle.net/2440/140208
Title: Cambrian Sauk transgression in the Grand Canyon region redefined by detrital zircons
Author: Karlstrom, K.; Hagadorn, J.; Gehrels, G.; Matthews, W.; Schmitz, M.; Madronich, L.; Mulder, J.; Pecha, M.; Giesler, D.; Crossey, L.
Abstract: The Sauk transgression was one of the most dramatic global marine transgressions in Earth history. It is recorded by deposition of predominantly Cambrian non-marine to shallow marine sheet sandstones unconformably above basement rocks far into the interiors of many continents. Here we use dating of detrital zircons sampled from above and below the Great Unconformity in the Grand Canyon region to bracket the timing of the Sauk transgression at this classic location. We find that the Sixtymile Formation, long considered a Precambrian unit beneath the Great Unconformity, has maximum depositional ages that get younger up-section from 527 to 509 million years old. The unit contains angular unconformities and soft-sediment deformation that record a previously unknown period of intracratonic faulting and epeirogeny spanning four Cambrian stages. The overlying Tapeats Sandstone has youngest detrital zircon ages of 505 to 501 million years old. When linked to calibrated trilobite zone ages of greater than 500 million years old, these age constraints show that the marine transgression across a greater than 300-km-wide cratonic region took place during an interval 505 to 500 million years ago—more recently and more rapidly than previously thought. We redefine this onlap as the main Sauk transgression in the region. Mechanisms for this rapid flooding of the continent include thermal subsidence following the final breakup of Rodinia, combined with abrupt global eustatic changes driven by climate and/or mantle buoyancy modifications.
Description: Published online: 28 May 20182018-01-01T00:00:00ZOptically stimulated luminescence dating using quartz
https://hdl.handle.net/2440/139932
Title: Optically stimulated luminescence dating using quartz
Author: Murray, A.; Arnold, L.J.; Buylaert, J.-P.; Guérin, G.; Qin, J.; Singhvi, A.K.; Smedley, R.; Thomsen, K.J.
Abstract: Optically stimulated luminescence (OSL) signals from quartz can be used to determine when sedimentary archives were deposited. OSL dating uses the accumulation of energy stored in a crystal structure to measure time. This stored energy is absorbed from ionizing radiation, and is released (reset) by heat or daylight. The total specific energy (dose) absorbed since the last resetting is measured using OSL, and divided by the rate of storage (dose rate) to give the time elapsed from the last heating or daylight exposure. In this Primer, quartz OSL dating is introduced and the signal resetting processes outlined. We describe the origins and quantification of the dose rate and the daylight-sensitive OSL signal most appropriate to dose estimation. The most widely used dose measurement method is then discussed, together with quality-control procedures. A broad set of geological and archaeological studies are used to illustrate the wide range of potential applications, and we describe the challenges arising from different deposition environments and summarize evidence for the precision and accuracy of published ages. Uncertainties and minimum reporting are discussed together with methodological limitations, particularly when applied to young and old sediments. Finally, we highlight the anticipated future developments in the field.2021-01-01T00:00:00ZIn-situ Lu-Hf geochronology of calcite
https://hdl.handle.net/2440/139914
Title: In-situ Lu-Hf geochronology of calcite
Author: Simpson, A.; Glorie, S.; Hand, M.; Spandler, C.; Gilbert, S.; Cave, B.
Abstract: The ability to constrain the age of calcite formation is of great utility to the Earth science community, due to the ubiquity of calcite across a wide spectrum of geological systems. Here, we present the first in situ laser ablation inductively coupled tandem quadrupole mass spectrometry (LA-ICP-MS/MS) Lu–Hf ages for calcite, demonstrating geologically meaningful ages for iron oxide copper gold (IOCG) and skarn mineralisation, carbonatite intrusion, and low-grade metamorphism. The analysed samples range in age between ca. 0.9 and ca. 2 Ga with uncertainties between 1.7 % and 0.6 % obtained from calcite with Lu concentrations as low as ca. 0.5 ppm. The Lu–Hf system in calcite appears to be able to preserve primary precipitation ages over a significant amount of geological time, although further research is required to constrain the closure temperature. The in situ approach allows calcite to be rapidly dated while maintaining its petrogenetic context with mineralisation and other associated mineral processes. Therefore, LA-ICP-MS/MS Lu–Hf dating of calcite can be used to resolve the timing of complex mineral paragenetic sequences that are a feature of many ancient rock systems.
Description: Published: 8 June 20222022-01-01T00:00:00ZThermal history of the East Antarctic margin: Campaign-style apatite U-Pb and fission track study
https://hdl.handle.net/2440/139910
Title: Thermal history of the East Antarctic margin: Campaign-style apatite U-Pb and fission track study
Author: Mayer-Ullmann, F.; Glorie, S.; Mulder, J.; Hand, M.; Morrissey, L.; Verhaert, S.; Halpin, J.2023-01-01T00:00:00Z