scholarly journals Exhumation and erosion of the Northern Apennines, Italy: new insights from low-temperature thermochronometers

2021 ◽  
Author(s):  
Erica D. Erlanger ◽  
Maria Giuditta Fellin ◽  
Sean D. Willett
Keyword(s):  
Temporal Pattern ◽  
Fission Track ◽  
Vitrinite Reflectance ◽  
Kinematic Model ◽  
Northern Apennines ◽  
Burial Depth ◽  
Apatite Fission Track ◽  
Erosion Rates ◽  
Orogenic Wedge ◽  
Reflectance Data

Abstract. Analysis of new detrital apatite fission-track (AFT) ages from modern river sands, published bedrock and detrital AFT ages, and bedrock apatite (U-Th)/He (AHe) ages from the Northern Apennines provide new insights into the spatial and temporal pattern of erosion rates through time across the orogen. The pattern of time-averaged erosion rates derived from AHe ages from the Ligurian side of the orogen illustrates slower erosion rates relative to AFT rates from the Ligurian side and relative to AHe rates from the Adriatic side. These results are corroborated by an analysis of paired AFT and AHe thermochronometer samples, which illustrate that erosion rates have generally increased through time on the Adriatic side, but decreased through time on the Ligurian side. Using an updated kinematic model of an asymmetric orogenic wedge, with imposed erosion rates on the Ligurian side that are a factor of two slower relative to the Adriatic side, we demonstrate that cooling ages and maximum burial depths are able to replicate the pattern of measured cooling ages across the orogen and estimates of burial depth from vitrinite reflectance data. These results suggest that horizontal motion is an important component of the overall rock motion in the wedge, and that the asymmetry of the orogen has existed for at least several million years.

THERMAL MODELLING IN THE EASTERN OTWAY BASIN

1993 ◽  
Vol 33 (1) ◽  
pp. 205 ◽  
Author(s):  
G.T. Cooper ◽  
K.C. Hill ◽  
M. Wlasenko
Keyword(s):  
Lower Cretaceous ◽  
Fission Track ◽  
Rapid Heating ◽  
Vitrinite Reflectance ◽  
Seismic Profile ◽  
Thermal Maturity ◽  
Apatite Fission Track ◽  
Fission Track Analysis ◽  
Reflectance Data ◽  
Track Analysis

Vitrinite reflectance data across the Otway Ranges yield a thermal maturity map that indicates the presence of a broad NE-SW trending anticline with strong vergence to the southeast. Surface Rv max values for the central part of the ranges are >1.5 whilst those on both limbs decrease to Apatite fission track analysis of seven Eumeralla (Lower Cretaceous) samples from the coast around Wye River yields an AFTA age of 90±5 Ma, consistent with similar cooling ages measured around most of the SE Australia margin. Modelling of the data is consistent with a stratigraphic age of -100 Ma, rapid heating to −80°C for −5 Ma followed by cooling from 95–80 Ma and further cooling in the Miocene.Geologically the very large asymmetric anticline can be explained by inversion of a thick rift sequence along a major, listric northwest-dipping fault, perhaps soling at mid-crustal levels. This is consistent with structures observed offshore in the Torquay Embayment and is being tested by the AGSO deep seismic profile BMR 920T1. Observed gravity highs in the Otway Ranges may be associated with inverted high density sediments. Fission track analysis indicates that the major cooling was at −90 Ma, which is therefore likely to be the time of inversion. However, this implies compression during continental breakup, the mechanisms of which are not fully understood.

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