We present a set of six time-temperature (tT) histories, called benchmark paths, that can be used as a shared framework for evaluating the sensitivity of a thermochronologic system to the variables inherent in the interpretation of thermochronologic data (e.g., kinetics models, mineral compositions or geometries, etc.) . These benchmark paths span 100 Myr, include monotonic and nonmonotonic histories that represent plausible geologic scenarios, and have a range of cooling rates through different chronometer partial-retention/annealing temperatures. Here, we demonstrate their utility by presenting a method for tuning these paths to 11 different kinetics models for the apatite (U-Th-Sm)/He (n=5), apatite fission-track (n=2), and zircon (U-Th)/He (n=4) systems. These tuned tT paths provide a practical comparison of the kinetics models for each system and the data patterns they predict, thereby offering anyone performing thermal history analysis the ability to consider how their choice of kinetics model may impact their data interpretation. The adoption of benchmark paths for evaluating kinetics models and other variables provides a practical way for the thermochronology community to evaluate and communicate the decision making processes that are inherent in thermochronologic modeling and data interpretation.

Recent advances in low-temperature thermochronology enable the recovery of deep-time thermal histories from Precambrian crystalline rocks shaped by multiple tectonic events, offering unprecedented opportunities to test tectonic hypotheses and links to significant biologic and climatic episodes. In particular, the late Neoproterozoic breakup of supercontinent Rodinia profoundly shaped the western margin of Laurentia, leaving a geologic record along the Cordilleran hingeline that temporally associates continental rifting with biological change at the Ediacaran-Cambrian transition and may explain the unusual eastern extent of the Laramide orogeny. However, sedimentary evidence east of the Cordilleran hingeline is lacking, leaving postulated links untested. Here we interpret Neoproterozoic to recent tectonic histories from the Colorado Front Range using thermal history modeling of zircon (U-Th)/He (ZHe) ages (50-607 Ma), which vary with grain U-Th composition. These models are constrained by geologic records that place basement rocks near Earth's surface at ca. 700, 500, and 300 Ma, and they resolve late Neoproterozoic heating to 240-285 degrees C followed by cooling. Sensitivity tests confirm this heating signal depends on fitting Mesoproterozoic 40Ar/39Ar ages and a ZHe data set that includes high-U-Th grains with reproducible 61 +/- 7.5 Ma ages that correspond to Colorado Mineral Belt magmatism and Laramide exhumation. We interpret the Neoproterozoic heating as direct evidence that intracontinental rifting in the Front Range region drove kilometer-scale burial coeval with global glaciation and the fragmentation of Rodinia. The magnitude and duration of reheating are well constrained, but resolving subsequent cooling during Neoproterozoic-Paleozoic time strongly depends on surface constraints from the geologic record.

Advances in low-temperature thermochronology have made it applicable to a plethora of geoscience investigations. The development of modeling programs (e.g., QTQt and HeFTy) that extract thermal histories from thermochronologic data has facilitated growth of this field. However, the increasingly wide range of scientists who apply these tools requires an accessible entry point to thermal history modeling and how these models develop our understanding of complex geological processes. This contribution offers a discussion of modeling strate-gies, using QTQt, including making decisions about model design, data input, kinetic parameters, and other factors that may influence the model output. We present a suite of synthetic data sets derived from known thermal histories with accompanying tutorial exercises in the Supplemental Material1. These data sets illustrate the opportunities and limitations of thermal history mod-eling. Examining these synthetic data helps to develop intuition about which thermochronometric data are most sensitive to different thermal events and to what extent user decisions on data handling and model set -up can control the recovery of the true solution. We also use real data to demonstrate the importance of incorporating sensitivity testing into thermal history modeling and suggest several best practices for exploring model sensitivity to factors including, but not limited to, the model design or inversion algorithm, geo-logic constraints, data trends, the spatial relationship between samples, or the choice of kinetics model. Finally, we provide a detailed and explicit workflow and an applied example for a method of interrogating vague model results or low observation-prediction fits that we call the "Path Structure Approach." Our explicit examination of thermal history modeling practices is designed to guide modelers to identify the factors controlling model results and demonstrate reproducible approaches for the interpretation of thermal histories.

Earth and Space Science Open Archive Society Material ReportOpen AccessYou are viewing the latest version by default [v1]Report from the 17th International Conference on ThermochronologySocieties & AuthorsRichard AKetchamiDMarissaTremblayiDAlyssaAbbeyJaclynBaughmaniDEmilyCooperdockiDGilbyJepsoniDKendraMurrayiDMargaretOdlumJessicaStanleyiDOliviaThurstoniDSee all authors American Geophysical UnionCorresponding AuthorAmerican Geophysical Unionhttps://www.agu.orgview email addressThe email was not providedcopy email addressRichard A KetchamiD• Submitting AuthorUniversity of Texas at AustiniDhttps://orcid.org/0000-0002-2748-0409view email addressThe email was not providedcopy email addressMarissa TremblayiDPurdue UniversityiDhttps://orcid.org/0000-0001-9984-9554view email addressThe email was not providedcopy email addressAlyssa AbbeyCalifornia State University, Long Beachview email addressThe email was not providedcopy email addressJaclyn BaughmaniDCalifornia State Polytechnic University, HumboldtiDhttps://orcid.org/0000-0003-1728-2481view email addressThe email was not providedcopy email addressEmily CooperdockiDUniversity of Southern CaliforniaiDhttps://orcid.org/0000-0002-0154-8719view email addressThe email was not providedcopy email addressGilby JepsoniDUniversity of ArizonaiDhttps://orcid.org/0000-0003-0151-3062view email addressThe email was not providedcopy email addressKendra MurrayiDIdaho State UniversityiDhttps://orcid.org/0000-0003-4008-1645view email addressThe email was not providedcopy email addressMargaret OdlumUniversity of Nevada, Las Vegasview email addressThe email was not providedcopy email addressJessica StanleyiDUniversity of IdahoiDhttps://orcid.org/0000-0001-8463-9271view email addressThe email was not providedcopy email addressOlivia ThurstoniDIndiana University at BloomingtoniDhttps://orcid.org/0000-0003-3928-0858view email addressThe email was not providedcopy email address

Establishing the timing of surface uplift in the Central Andes is essential for evaluating the geodynamic mechanisms responsible for mountain building and their role in the development of dry conditions along the western coasts of Peru and Chile. Here, we present new stable hydrogen isotopic values from stream waters and hydration water in volcanic glass from northern Chile (18.5–19.5°S) that show that the Western Cordillera was already elevated by the early Miocene. The hydrogen isotopic values of reconstructed surface waters obtained from ancient and modern volcanic glass indicate that the Western Cordillera in northern Chile attained modern elevations by at least 22.8 Ma. When combined with paleoaltimetric records from the Altiplano and northwestern Puna, these results demonstrate that surface uplift of the Andean plateau was a time-transgressive process that varied not just from west to east but also from north and south along the strike of the orogen. Our paleoaltimetry reconstruction also suggests that the Western Cordillera has blocked moisture coming from the east since at least the early Miocene, consistent with previously published evidence of arid-semiarid conditions in the Atacama Desert. However, hyperaridity on the western Andean slope developed later and appears to correspond with the timing of uplift in the Eastern Cordillera and Altiplano. Our results suggest that the growth of the Central Andean rain shadow relied not only on the elevation of the Western Cordillera but also on the widening of the plateau.

Earth and Space Science Open Archive PosterOpen AccessYou are viewing the latest version by default [v1]Navigating the modelling puzzle: Using forward and inverse models to make clear decisions when exploring and interpreting cooling ages in both HeFTy and QTQt.AuthorsAlyssa LangfordAbbeyiDKendraMurrayAndreaStevens GoddardiDMarkWildmanSee all authors Alyssa Langford AbbeyiDCorresponding Author• Submitting AuthorCalifornia State University Long BeachiDhttps://orcid.org/0000-0002-0617-4859view email addressThe email was not providedcopy email addressKendra MurrayIdaho State Universityview email addressThe email was not providedcopy email addressAndrea Stevens GoddardiDIndiana University BloomingtoniDhttps://orcid.org/0000-0001-9405-7953view email addressThe email was not providedcopy email addressMark WildmanUniversity of Glasgowview email addressThe email was not providedcopy email address

Earth and Space Science Open Archive PosterOpen AccessYou are viewing the latest version by default [v1]Know (all!) your assumptions, investigate the sensitivities: Towards more rigorous thermal history modeling practicesAuthorsKendraMurrayiDNathanNiemiiDSee all authors Kendra MurrayiDCorresponding Author• Submitting AuthorIdaho State UniversityiDhttps://orcid.org/0000-0003-4008-1645view email addressThe email was not providedcopy email addressNathan NiemiiDUniversity of MichiganiDhttps://orcid.org/0000-0002-3380-3024view email addressThe email was not providedcopy email address

Inverse thermal history modeling is an effective tool to explore plausible time-temperature (t-T) histories that can be used to describe the geologic history of a sample. Although in some inverse m...

The Cenozoic history of crustal deformation, surface uplift, and erosion of the central Colorado Plateau (southwestern USA) is distinct from and relatively poorly understood compared with surrounding regions in the North American Cordillera, including the Grand Canyon region and the southwestern Plateau margin. Here, we present new apatite thermochronologic results from Paleozoic-Mesozoic sandstones sampled in the Canyonlands region—the interior of the Colorado Plateau in southeastern Utah. The apatite (U-Th-Sm)/He (He) ages are highly dispersed, with both positive-slope and negative-slope age-effective U (eU) trends. Samples with apatite He results suitable for thermal history modeling are from the Abajo and La Sal mountains intrusive complexes and the Permian, Triassic, and Jurassic rocks sampled near the Colorado River at Lees Ferry, Arizona, and Hite, Utah. Samples with the richest thermal history information have positive-slope apatite He age-[eU] trends, with ages ca. 10 to 5 Ma at [eU] < 10 ppm and ca. 25 to 20 Ma at [eU] > 60 ppm. Modeled thermal histories that best predict this pattern require two periods of rock cooling: one during the middle Cenozoic ca. 30 to 20 Ma and the other since the latest Miocene ca. 6 Ma. The most recent cooling documents the transition from a slowly eroding Miocene landscape to recent rapid erosion that likely postdates 6 Ma and the integration of the modern Colorado River. Middle Cenozoic rock cooling can be attributed to either ∼1 km of erosion between ca. 25 and 15 Ma, as previous workers have suggested in other parts of the Colorado Plateau region, or relaxation of a geothermal gradient transiently doubled by magmatism associated with the vigorous magmatic flare-up that swept through the region ca. 34 to 20 Ma. The ambiguity of using middle Cenozoic rock cooling as a proxy for erosion in this region means that this event should be described using a nongenetic term: the Middle Cenozoic Cooling Event.

Flood basalt volcanism involves large volumes of magma emplaced into the crust and surface environment on geologically short timescales. The mechanics of flood basalt emplacement, including dynamics of the crustal magma transport system and the tempo of individual eruptions, are not well constrained. Here we study two exhumed dikes from the Columbia River Flood Basalt province in northeast Oregon, USA, using apatite and zircon (U-Th)/He thermochronology to constrain dike emplacement histories. Sample transects perpendicular to the dike margins document transient heating of granitic host rocks. We model heating as due to dike emplacement, considering a thermal model with distinct melt-fraction temperature relationships for basaltic magma and granitic wallrock, and a parameterization of unsteady flow within the dike. We model partial resetting of thermochronometers by considering He diffusion in spherical grains as a response to dike heating. A Bayesian Markov-Chain Monte Carlo framework is used to jointly invert for six parameters related to dike emplacement and grain-scale He diffusion. We find that the two dikes, despite similar dimensions on an outcrop scale, exhibit different spatial patterns of thermochronometer partial resetting away from the dike. These patterns result in distinct predicted emplacement histories. We extend previous modeling of a presumed feeder dike at Maxwell Lake in the Wallowa Mountains of northeastern Oregon, finding posterior probability distribution functions (PDFs) that predict steady heating from sustained magma flow over $1-6$ years and elevated farfield host rock temperatures. This suggests regional-scale heating in the vicinity of Maxwell Lake, which might arise from nearby intrusions. The other dike, within the Cornucopia subswarm, is predicted to have a $1-4$ year thermally active lifespan with an unsteady heating rate suggestive of magma low flow rate compared to Maxwell Lake, in a cool near-surface thermal environment. In both cases, misfit of near-dike partial resetting of thermochronometers by models suggests either heat transfer via fluid advection in host rocks or pulsed magma flow in the dikes. Our results highlight the diversity of dike emplacement histories within the Columbia River Flood Basalt province and the power of Bayesian inversion methods for quantifying parameter trade-offs and uncertainty in thermal models.