The geologic interpretation of the detrital thermochronology record within a stratigraphic framework, with examples from the European Alps, Taiwan and the Himalayas

Abstract

Detrital thermochronology studies based on the lag-time approach are increasingly employed to investigate the erosional evolution of mountain belts and perform paleotectonic reconstructions starting from the analysis of sedimentary rocks. However, simple predictions of lag-time conceptual models are often in conflict with observations in sedimentary basins. In this review article, we discuss the major assumptions of the lag-time approach, and present conceptual models to illustrate the main factors that may influence the final complexity of the detrital thermochronologic record in a sedimentary basin. These factors include: (i) the original complexity of the thermochronologic age structure in the source region; (ii) mixing of detritus from multiple source regions characterized by different geologic evolution; (iii) modifications of the original thermochronologic fingerprint from source to sink; (iv) potential post-depositional annealing due to thick sedimentary burial. Based on this synthesis and discussion, we present a list of interpretive guidelines and fundamental criteria for the geologic interpretation of the detrital thermochronologic record derived from the erosion of single and mixed sources. These interpretive guidelines are then applied to published detrital thermochronology datasets from the European Alps, Taiwan and the Himalayas in order to illustrate benefits and pitfalls of the geologic interpretation of thermochronologic age trends through a stratigraphic succession. Results provide evidence for (i) non-steady-state exhumation of the European Alps, (ii) late Miocene onset of arc-continent collision in Taiwan, and (iii) late Miocene morphogenic phase of mountain building in the Himalaya. Concepts presented in this article reinforce existing approaches and provide new perspectives for the application of the detrital thermochronologic approach to tectonic settings where the geologic evolution may be poorly understood. As such, they are expected to guide geologists towards interpretations that are both consistent with evidence provided by different thermochronologic systems, and geologic evidence provided by the rock record.

Ongoing exhumation of the Taiwan orogenic wedge revealed by detrital apatite thermochronology: The impact of effective mineral fertility and zero-track grains

“…The lower part of the Plio-Pleistocene succession of the northern Coastal Range would thus reflect the early-stage removal of sedimentary cover rocks during the onset of arc-continent collision. The onset of fast erosion can be constrained as late Miocene, whereas the removal of the rock pile with a thermochronologic fingerprint acquired before the onset of arc-continent collision was likely completed by 2 Ma (Malusà and Fitzgerald 2020). In the southern Coastal Range, sediments from the 2-1 Ma stratigraphic interval are dominated by old ZFT age peaks (Kirstein et al 2014), which indicates that the rock pile with a thermochronologic fingerprint acquired before the onset of arc-continent collision was not completely removed 1 m.y.…”

“…In the late Miocene, fast erosion rates may have affected the accretionary wedge in front of the northern Coastal Range, followed 1 m.y. later by rapid erosion of the accretionary wedge in front of the southern Coastal Range (Malusà and Fitzgerald 2020),…”

“…The lesson learnt from detrital AFT analysis of Taiwan sediments can be applied to the interpretation of Bengal Fan AFT data recently published by Huyghe et al (2020). Bengal As suggested by Malusà and Fitzgerald (2020), this may be ascribed either to a fertility bias or to the underestimation of zero-track grains during analysis and subsequent data interpretation. Figure 9B shows, on the left, the mid-Bengal Fan lag-time diagram based on AFT central ages as proposed by Huyghe et al (2020).…”

Thermal record of the building of an orogen in the retro‐foreland basin: Insight from basement and detrital thermochronology in the eastern Pyrenees and the north Pyrenean basin (France)

“…Low‐temperature thermochronology (LTT) methods, such as apatite fission track and (U‐Th‐Sm)/He, provide important constraints when interpreting complex geological histories and when identifying the main phases of development of mountain belts throughout the erosion phase of the first 1–4 km of depth (e.g. Ault et al., 2019; Malusà & Fitzgerald, 2020). Detrital LTT applications, in particular, on syn‐orogenic sediments in foreland basins give us insight into the spatio‐temporal evolution from the source to the basin and the erosional processes responsible for sediment production (Filleaudeau et al., 2012; Odlum et al., 2019; Thomson et al., 2017; Whitchurch et al., 2011; Willingshofer et al., 2001).…”

Role of the Down-Bending Plate as a Detrital Source in Convergent Systems Revealed by U–Pb Dating of Zircon Grains: Insights from the Southern Andes and Western Italian Alps

“…These studies include a variety of tools whose choice depends on a number of factors like the expected lithology of eroded rocks, the grain size of eroded sediment (gravel vs. sand vs. mud), and so forth. Among these tools, spanning from pebble clast petrology to mudstone and isotope geochemistry (i.e., Sm-Nd and Rb-Sr systems, [7]), the geo-thermochronology of specific types of sand-size clastic heavy minerals has rapidly developed and is now a standardized procedure (see [8] for an up-to-date review).…”