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| Titel |
New terrace ages better constrain the uplift history for the Mejillones Peninsula, northern Chile |
| VerfasserIn |
Ariane Liermann, Tibor Dunai, Steven Binnie, Stefan Heinze, Alfred Dewald, Pia Victor, Gabriel Gonzalez |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250077541
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| Zusammenfassung |
| The Mejillones Peninsula is a promontory extending spectacularly from the northern Chilean
coastline. The peninsula is marked by well preserved marine terraces extending from just
above sea-level to greater than 400 m. These staircased planar expressions result from a
combination of glacioeustatic sea-level fluctuation and tectonic uplift. It has been shown by
several studies that such terraces are formed during interglacial marine high-stands and are
preserved because of abandonment in intervening sea-level low-stands. Post Mid Pleistocene
transition high-stands (MIS 1 to 19) were within 10 m of the current sea-level (Siddall et al.
2006). We present cosmogenic 10Be exposure ages from marine pebbles deposited on the
surface of the terraces when they were at sea-level in order to constrain the uplift history of
the northwestern highland part of the peninsula. Based on the mean age (n=10) of the oldest
terrace measured (~140 m) we obtain an average uplift rate of ~0.3 m/ka for the last
~465 ka. This average uplift rate can be subdivided into a recent slower and an
older, more rapid rate. The average uplift rate between ~465 and ~280 ka was
~0.6 m/ka, and based on the observed linear increase in age with altitude the uplift
was steady throughout this period. However, for the last ~280 ka we calculate
a slower uplift rate of ~0.1 m/ka. Tracing the surface expressions of the marine
terraces northwards we observe an anomalous increase of >100 m elevation over
length-scales of ~2 km. This suggests different amounts of tectonic uplift for adjacent
regions within the northern part of the peninsula. From a single terrace surface
(288m) in the more elevated region we measured an exposure age of ~405 ka,
compatible with the temporal framework of uplift defined by the lower elevation ages.
However, the higher altitude of this terrace, in comparison to the adjacent, lower region
suggests a more rapid rate of uplift (~0.7 m/ka) and thus differential uplift within the
northern part of the peninsula in recent times. The ~0.1 m/ka rate of uplift we
measure over the last ~280 ka is similar to other estimates for the regional uplift
rate of the north Chilean coastline (~0.2 m/ka). However, the high uplift rates of
the northern tip of the Mejillones peninsula, ~0.7 m/ka, significantly exceeds this
value.
Siddall, M., J. Chappell and E.-K. Potter (2006). Eustatic Sea Level During Past
Interglacials. The climate of past interglacials. F. Sirocko, M. Claussen, T. Litt and M. F.
Scanchez-Goni. Amsterdam, Elsevier. 7: 75-92. |
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