Maximizing Inverse Thermal History Model Results as a Strategy for
Effective Geologic Interpretations
Abstract
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 modeling
exercises the input thermochronology data is consistent with a single
set of t-T histories with similar heating and cooling trends, more
commonly inverse models identify a range of paths with different and
distinct heating and cooling histories but similarly good fits to the
data. Each set of these “path families” typically requires a different
geologic interpretation to explain the observed heating and cooling
trend, so it is important to identify and consider all possible path
families consistent with the regional geology that fit the modelled
dataset before selecting a preferred geologic interpretation. Although
the inverse model results are always consistent with measured data, a
model’s ability to detect all possible path families is partly
controlled by the model design – for example the choice of initial
conditions, monotonicity settings, and forced time-temperature windows.
In this exercise using the thermal history modeling program HeFTy, we
illustrate the effects of model design on the inverse model results of a
set of multi-chronometer datasets from the southern Patagonian Andes. We
use model design to maximize the number of path families identified
through inverse modeling. Once individual paths are classified according
to path families, we use independently constrained regional geology to
discriminate among the diverse plausible set of path families and
evaluate different available geologic scenarios. Our exercise
illustrates that models restricting exploration of all path families may
not identify the true cooling history of the sample. Initially, it may
appear challenging to interpret inverse model results that include
multiple path families, but we argue that iterating between independent
geologic data and modeling provides an effective tool to test the
geologic plausibility of alternative heating and cooling histories.
Although this exercise is executed using HeFTy, maximizing the
identification of all possible path families should be an important
component of model design in inverse modeling exercises using all
inverse modeling programs.