Geomorphology can have a strong influence on thermochronometer. In particular, the closure isotherm will tend to form a smoothed version of the surface topography, with greater topographic relief producing larger deflections of the isotherm. Also, erosion rate will influence the mean closure depth given that the faster erosion causes isotherms to migrate to shallower depths. We report on modeling here using the PECUBE software (Braun, 2003), in which we solved the heat transport equation in three dimensions by conduction and advection together with an evolving surface topography, to constrain the evolution of surface relief in the Northern Apennines. In particular, we wish to constrain the decrease in surface topography that may have occurred during the emergence of the orogen as it started interacting with the Apulian margin some 5-10 Myr ago. The Neighbourhood Algorithm (or NA) (Sambridge, 1999) is used to constrain the values of free parameters (i.e. time at which the relief starts to decrease, amount of topography decrease, crustal elastic thickness) by minimizing a misfit function derived from observed and modeled ages. We used a 128-node cluster of PCs to sample parameter space in a meaningful way. Dataset comprises zircon and apatite fission-track and zircon and apatite (U-Th)/He ages obtained through the Northern Apennine chain. The spatial distribution of ages shows a decrease eastwards, with the oldest apatite fisison-track ages of about 11 Ma to the west and the youngest of about 3 Ma along the central range. Results obtained by NA inversion indicate that the dataset can be equally explained with low values of the relief loss and elastic plate thickness or higher values of the relief loss and elastic plate thickness. However, beacuse many of He ages and the general pattern of younger ages near the central axis of the orogen are not well reproduced in the predictions, a detailed investigation of age-elevation relationships suggests that a model in which the denudation is solely driven by surface erosion and isostasy is not appropriate for this chain. The thermochronological dataset is better explained by a model in which relief reduction associated with the emergence of the wedge is accompanied by ongoing tectonic uplift.
Thermal-topographic modeling of the Northern Apennines
ZATTIN, MASSIMILIANO;
2004
Abstract
Geomorphology can have a strong influence on thermochronometer. In particular, the closure isotherm will tend to form a smoothed version of the surface topography, with greater topographic relief producing larger deflections of the isotherm. Also, erosion rate will influence the mean closure depth given that the faster erosion causes isotherms to migrate to shallower depths. We report on modeling here using the PECUBE software (Braun, 2003), in which we solved the heat transport equation in three dimensions by conduction and advection together with an evolving surface topography, to constrain the evolution of surface relief in the Northern Apennines. In particular, we wish to constrain the decrease in surface topography that may have occurred during the emergence of the orogen as it started interacting with the Apulian margin some 5-10 Myr ago. The Neighbourhood Algorithm (or NA) (Sambridge, 1999) is used to constrain the values of free parameters (i.e. time at which the relief starts to decrease, amount of topography decrease, crustal elastic thickness) by minimizing a misfit function derived from observed and modeled ages. We used a 128-node cluster of PCs to sample parameter space in a meaningful way. Dataset comprises zircon and apatite fission-track and zircon and apatite (U-Th)/He ages obtained through the Northern Apennine chain. The spatial distribution of ages shows a decrease eastwards, with the oldest apatite fisison-track ages of about 11 Ma to the west and the youngest of about 3 Ma along the central range. Results obtained by NA inversion indicate that the dataset can be equally explained with low values of the relief loss and elastic plate thickness or higher values of the relief loss and elastic plate thickness. However, beacuse many of He ages and the general pattern of younger ages near the central axis of the orogen are not well reproduced in the predictions, a detailed investigation of age-elevation relationships suggests that a model in which the denudation is solely driven by surface erosion and isostasy is not appropriate for this chain. The thermochronological dataset is better explained by a model in which relief reduction associated with the emergence of the wedge is accompanied by ongoing tectonic uplift.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
