Erosion rates in the source region of an ancient sediment routing system: comparison of depositional volumes with thermochronometric estimates

Abstract

Calculation of the total depositional volume of an ancient source-to-sink system, combined with estimates of the area of catchments acting as source regions using provenance methods, is used to evaluate average catchment erosion rates on a million year time scale. These rates are compared with values derived from thermochronological methods. Using the mid-to late Eocene (33.9-41.6 Ma) Escanilla palaeo-sediment routing system from the south-central Pyrenean orogenic wedge-top zone as an example, c. 3500 ± 300 km 3 of solid particulate sediment was derived from two catchments in the south-central Pyrenees over a 7.7 myr period, equivalent to a mean erosion rate of c. 0.15-0.18 mm a −1 . Average exhumation rates in contributing catchments over the same time interval are estimated at 0.2-0.3 mm a −1 based on apatite fission-track analysis of pebbles in proximal conglomerates, and 0.23-0.34 mm a −1 from fission-track analysis of detrital apatites sampling a wider range of grain size. Sediment supply progressively increased during the mid-to late Eocene time period, at least in part driven by catchment expansion deep into the Pyrenean Axial Zone at c. 39 Ma. The consistency of the rates of catchment-averaged erosion calculated from different methods builds confidence that source areas have been connected to depositional sinks correctly.

Mass-Balance Constraints On Stratigraphic Interpretation of Linked Alluvial-Coastal-Shelfal Deposits From Source To Sink: Example From Cretaceous Western Interior Basin, Utah and Colorado, U.S.A

“…(3) The mass-balance analysis has the potential to be integrated with first-order estimates of drainage area to constrain the sediment routing system from source to sink (e.g., Fig. 14) (e.g., Michael et al 2014b). Although this aspect is not explored fully here, we are able to estimate drainage-area sizes for the studied strata that are consistent with provenance constraints, using a variety of empirical relationships and measurements that are readily obtained from geologic data.…”

“…In a later section, we use our results to estimate catchment area using empirical geomorphic relationships derived from submodern routing systems (e.g., Sømme et al 2009a;Blum et al 2013). However, in this case study, we lack thermochronometric data that constrain longterm (Myr) average erosion rates of the catchment, which can be used as an independent check of depositional volumes and masses (e.g., Michael et al 2014b).…”

Are landscapes buffered to high-frequency climate change? A comparison of sediment fluxes and depositional volumes in the Corinth Rift, central Greece, over the past 130 k.y.

“…Sediment supply from source regions is a fundamental control on the stratigraphic record (Gawthorpe and Leeder, 2000;Allen, 2008a;Blum and Hattier-Womack, 2009;Armitage et al, 2011;Covault et al, 2011;Allen et al, 2013;Hampson et al, 2014;Michael et al, 2014;Romans et al, 2016). In areas of active extension, landscape and rift evolution models have all shown the importance of tectonics in driving the volume, grain size, and character-istics of sediment supply to depocenters (e.g., Humphrey and Heller, 1995;Allen and Densmore, 2000;Gawthorpe and Leeder, 2000;Densmore et al, 2003;Cowie et al, 2006;Backert et al, 2010).…”

Strata and time: probing the gaps in our understanding

“…Landscape evolution and the resultant mass flux of sediment towards the sink area must be reconstructed from a variety of proxies such as detrital heavy minerals, strontium isotope ratios, U -Pb and fission-track dating of detrital zircon crystals (e.g. Michael et al 2014).…”