ABSTRACT In this study, we determined the timing of burial and subsequent exhumation of Barrovian metamorphic rocks from the Chloride Cliff area of the Funeral Mountains in southeastern California by constraining the ages of different portions of a pressure-temperature ( P-T ) path. Using a split-stream laser-ablation inductively coupled plasma–mass spectrometry (ICP-MS) system, we analyzed 192 domains from 35 grains of monazite within five samples with a spot size of 8 µm to determine U-Pb ages and trace-element abundances from the same samples (same polished sections) that were analyzed to produce the P-T paths. Changes that took place within individual monazite grains reflect localized equilibrium and captured the changes in heavy rare earth element (HREE) abundances in the matrix reservoir that occurred as garnet grew, resorbed, and then regrew, thus constraining ages on different portions of the P-T path. The results show that garnet began growing ca. 168 Ma, began resorbing ca. 160 Ma, began retrograde regrowth ca. 157 Ma, and continued to regrow at least through ca. 143 Ma. The early garnet growth corresponds to a period of pressure increase along the P-T path. The subsequent partial resorption corresponds to the prograde crossing of a garnet-consuming reaction during decompression, and the retrograde garnet regrowth occurred when this same reaction was recrossed in the retrograde sense during further decompression. These results are consistent with previously determined ages, which include a Lu-Hf garnet age of 167.3 ± 0.72 Ma for the early pressure-increase portion of the P-T path, and 40 Ar/ 39 Ar muscovite cooling ages of 153 and 146 Ma in the lower-grade Indian Pass area 10 km southeast of Chloride Cliff. The 40 Ar/ 39 Ar muscovite ages document cooling at the same time as retrograde garnet regrowth was taking place at Chloride Cliff. The oldest monazite age obtained in this study, 176 ± 5 Ma, suggests that southeast-directed thrusting within the Jurassic retroarc was ongoing by this time along the California portion of the western North American plate margin, as a consequence of east-dipping subduction and/or arc collision. The Funeral Mountains were likely located on the east side of the northern Sierra Nevada range in the Jurassic, taking into account dextral strike-slip displacement along the Cretaceous Mojave–Snow Lake fault. The Late Jurassic timing of burial in the Funeral Mountains and its Jurassic location suggest burial was associated with the East Sierran thrust system. The timing of prograde garnet resorption during exhumation (160–157 Ma) corresponds to a change from regional dextral transpression to sinistral transtension along the Jurassic plate margin inferred to have occurred ca. 157 Ma. The recorded exhumation was concurrent with intrusion of the 148 Ma Independence dike swarm in the eastern Sierra Nevada and Mojave regions, which developed within a regime of northeast-southwest extension.

ABSTRACT This field trip is designed to highlight recent findings in regard to the tectonic history of the southern Death Valley region. During the first day, stops will take place in the Ibex Hills and adjacent Ibex Pass area. These stops were chosen to emphasize recent work that supports multiple phases of extension in the region, and is recorded by the interactions of complexly overprinted normal faults. Mapping of the Ibex Hills revealed an older set of normal faults that have a down-to-the-SW sense of movement and are cross-cut by down-to-the-NW style normal faults. Additionally, the Ibex Pass basin poses a number of questions regarding its stratigraphy and how it relates to the timing and kinematics of the region. Multiple stops within the basin will show the variation of volcanic and sedimentary units across Ibex Pass. The second day of the field trip is focused more so on the more recent transtensional and strike-slip history of southern Death Valley. In particular, recent mapping has correlated features in the Avawatz and Owlshead Mountains that indicate ~40k m of offset along the Southern Death Valley Fault Zone (SDVFZ). Stops will take place along traces of the SDVFZ in the Avawatz Mountains and the Noble Hills. The final stop of the trip is in the Mormon Point turtleback, where the implications of the SDVFZ offset are discussed, alongside the metamorphic rocks at the stop, suggesting the restoration of the Panamint Range partially atop the Black Mountains.