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| Titel |
Biostratigraphic evidence for dramatic Holocene uplift of Robinson Crusoe Island, Juan Fernández Ridge, SE Pacific Ocean |
| VerfasserIn |
P. Sepúlveda, J. P. Roux, L. E. Lara, G. Orozco, V. Astudillo |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 6 ; Nr. 12, no. 6 (2015-03-27), S.1993-2001 |
| Datensatznummer |
250117883
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| Publikation (Nr.) |
 copernicus.org/bg-12-1993-2015.pdf |
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| Zusammenfassung |
| Hotspot oceanic islands typically experience subsidence due to several
processes related to migration of the oceanic plate away from the mantle
plume and surface flexural loading. However, many other processes can
interrupt subsidence, some of which may be associated with catastrophic
events. A study of the biostratigraphy and sedimentology of Holocene deposits
on Robinson Crusoe Island (RCI) on the Juan Fernández Ridge (JFR) indicated
that dramatic uplift has occurred since 8000 years BP, at a rate of about
8.5mm yr-1. This is evidenced by supratidal flats with tepee
structures and sand layers containing marine gastropods (mostly
Nerita sp.) that are now exposed ca. 70 m a.s.l. The active
hotspot is located 280 km further west and the last volcanic activity on RCI
occurred at ca. 800 000 years BP. Long-term subsidence is evidenced by deep
submerged marine abrasion terraces at RCI. As no direct evidence was found
for the existence of a compensating bulge generated by the present hotspot
upon which RCI would be situated, it must be concluded that subsidence in the
wake of the mantle plume beneath the migrating plate was interrupted by very
rapid uplift, but on a scale that did not fully compensate for the previous
subsidence. This can be attributed to large-scale landslides followed by
isostatic rebound, although this is only vaguely reflected in the
low-resolution bathymetry of the area. To determine if this mechanism
produced the uplift, a detailed bathymetric survey of the area will be
required. If such a survey confirms this hypothesis, it may have implications
for the short-term dynamics of vertical variations of oceanic edifices and
their related effects on ecosystems and human population. |
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