Deciphering exhumation and burial history with multi‐sample down‐well thermochronometric inverse modelling

Abstract

The ability of thermochronometric data to shed light on the geologic history of samples and localities through thermal history inverse modelling is enhanced by the degree to which additional geological information can be incorporated into the modelling process. In this contribution, we describe a new set of methods and processes implemented in the HeFTy modelling software for specifying the stratigraphic relationships between samples down a well or borehole, allowing them to be modelled simultaneously, and demonstrate their use in bringing better definition to both predepositional and burial histories. Data from two wells in the Colombian Andes are examined, one in the Middle Magdalena Valley that experienced not only fast Miocene burial but also features a Mio-Pliocene unconformity, and one in the eastern foothills of the Eastern Cordillera in which burial was accomplished by a combination of sedimentation and overthrusting. Multiple-sample modelling in both wells considerably refines the results that are obtained from single-sample modelling. We also demonstrate how to use these methods to pose and evaluate distinct hypotheses concerning the geologic history. As a general rule, it is best practice to set up thermal history inverse models to pose specific geological questions while ruling out geologically impossible or inconsistent solutions.

Multiple Exhumation Phases in the Central Pontides (N Turkey): New Temporal Constraints on Major Geodynamic Changes Associated With the Closure of the Neo‐Tethys Ocean

“…To unravel the Cenozoic spatiotemporal pattern of fault‐related exhumation, we have combined low‐temperature thermochronology, including apatite fission track (AFT), zircon and apatite (U‐Th‐Sm)/He (ZHe and AHe, respectively), and geochronology (zircon U‐Pb) with thermal modeling using HeFTy (Ketcham, ; Ketcham et al, ). Thirty‐six samples were collected from five elevation profiles spanning 400 to 800 m of topographic relief along the Sinop Range (Sakarya Zone; Figures and ).…”

“…Inverse thermal modeling programs (e.g., HeFTy, Ketcham, ;s Ketcham et al, , ; and QTQt, Gallagher, ) offer the possibility to investigate time‐temperature paths that are consistent with thermochronology data and hence evaluate potential exhumation histories. In the newest version of HeFTy (v. 1.9.1, Ketcham et al, ), it is possible to perform thermal modeling of not only single samples but also elevation profiles of samples, considering the most elevated sample to be at 0‐m elevation (equivalent to the top of a well) and the lower samples as down‐well samples. Although thermal histories from inverse models do not directly consider perturbations of the geothermal gradient associated with topographic changes, variations in erosional efficiency, or shear heating and advection during faulting (e.g., Ehlers & Farley, ; Willett & Brandon, ), they appear to provide robust and consistent thermal histories (Ketcham et al, ).…”

Innovations in (U–Th)/He, Fission Track, and Trapped Charge Thermochronometry with Applications to Earthquakes, Weathering, Surface‐Mantle Connections, and the Growth and Decay of Mountains

“…FT and (U–Th)/He thermochronometry are now routinely applied to detrital minerals (e.g., Carter, , and references therein). Detrital apatite and/or zircon crystals can trace sediment sources in orogenic systems (Bernet & Garver, ; Glotzbach et al, ; Horton et al, ; Stock et al, ), quantify the basin burial and exhumation phases (Guenthner et al, ; Ketcham, Mora, & Parra, ; Schwartz et al, ), and track the source to sink evolution of sedimentary basins (Calzolari et al, ; Carter, ; Tranel et al, ; Zattin et al, ). Detrital thermochronometry from catchments also informs the timing and tempo of source area exhumation related to tectonism (e.g., Bernet et al, ; Bernet et al, ; Espurt et al, ; Filleaudeau et al, ; Gautheron, Espurt, et al, ), glacial processes (e.g., Ehlers et al, ; Enkelmann & Ehlers, ), or the interplay between the two.…”

Zircon, titanite, and apatite (U‐Th)/He ages and age‐eU correlations from the Fennoscandian Shield, southern Sweden

“…[]. This most recent version of HeFTy allows for the modeling of multiple samples separated by a vertical distance, like our borehole samples, and can be used to restrict the region of t‐T space that produces viable paths thereby improving the veracity of t‐T hypothesis testing [ Ketcham et al ., ]. In our data set, separating samples by depth, while also interrogating the observed age‐eU correlation, is difficult for reasons previously discussed in section 4.…”