Headward retreat of streams in the Late Oligocene to Early Miocene Swiss Alps

Schlunegger, Fritz; Norton, Kevin (2013). Headward retreat of streams in the Late Oligocene to Early Miocene Swiss Alps. Sedimentology, 60(1), pp. 85-101. Blackwell Science 10.1111/sed.12010

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This study uses the widths, the spacing and the grain-size pattern of Oligo/Miocene alluvial fan conglomerates in the central segment of the Swiss Alpine foreland to reconstruct the topographic development of the Alps. These data are analysed with models of longitudinal stream profile development, to propose that the Alpine topography evolved from an early transient state where streams adjusted to rock uplift by headward retreat, to a mature phase where any changes in rock uplift were accommodated by vertical incision. The first stage comprises the time interval between ca 31 Ma and 22 Ma, when the Alpine streams deposited many small fans with a lateral spacing of <30 km in the north Alpine foreland. As the range evolved, the streams joined and the fans coalesced into a few large depositional systems with a lateral spacing of ca 80 to 100 km at 22 Ma. The models used here suggest that the overall elevation of the Alps increased rapidly within <5 Myr. The variability in pebble size increased either due to variations in sediment supply, enhanced orographic effects, or preferentially due to a change towards a stormier palaeoclimate. By 22 Ma, only two large rivers carried material into the foreland fans, suggesting that the major Alpine streams had established themselves. This second phase of stable drainage network was maintained until ca 5 Ma, when the uplift and erosion of the Molasse started and streams were redirected both in the Alps and in the foreland. This study illustrates that sedimentological archives of foreland basins can be used to reconstruct the chronology of the topographic development of mountain belts. It is suggested that the finite elevation of mountainous landscapes is reached early during orogeny and can be maintained for millions of years, provided that erosion is efficient.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geological Sciences
08 Faculty of Science > Institute of Geological Sciences > Exogenous Geology

UniBE Contributor:

Schlunegger, Fritz and Norton, Kevin

Subjects:

500 Science > 550 Earth sciences & geology

ISSN:

0037-0746

Publisher:

Blackwell Science

Language:

English

Submitter:

Fritz Schlunegger

Date Deposited:

11 Aug 2014 11:03

Last Modified:

06 Oct 2015 11:28

Publisher DOI:

10.1111/sed.12010

Additional Information:

Special Issue: Alpine Sedimentology

Uncontrolled Keywords:

Alluvial fans, alpine erosion, Alps, headward erosion, Molasse Basin

BORIS DOI:

10.7892/boris.47068

URI:

https://boris.unibe.ch/id/eprint/47068

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