A drastic lower Miocene regolith evolution triggered by post obduction slab break-off and uplift in New Caledonia

A lower Miocene coarse conglomerate that crops out in the Népoui Peninsula does not represent the base of the marine transgression that followed obduction in New Caledonia. Instead, the conglomeratic alluvial fan that contains peridotite cobbles and reworked weathering products records a short‐lived...

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Bibliographic Details
Published in:Tectonics (Washington, D.C.) D.C.), 2014-09, Vol.33 (9), p.1787-1801
Main Authors: Sevin, Brice, Cluzel, Dominique, Maurizot, Pierre, Ricordel-Prognon, Caroline, Chaproniere, George, Folcher, Nicolas, Quesnel, Florence
Format: Article
Language:English
Subjects:
Alluvial fans
Earth Sciences
fluvial conglomerate
Geophysics
High pressure
Low temperature
Miocene
New Caledonia
peridotite
Plate tectonics
regolith
Sciences of the Universe
Sea level
Seismology
slab breakoff
Soil erosion
Subsidence
uplift
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Summary:A lower Miocene coarse conglomerate that crops out in the Népoui Peninsula does not represent the base of the marine transgression that followed obduction in New Caledonia. Instead, the conglomeratic alluvial fan that contains peridotite cobbles and reworked weathering products records a short‐lived episode of terrestrial erosion intercalated between two intervals of subsidence marked by marine carbonate deposition. Considering the Miocene sea level evolution reported in the literature, it is concluded that neither lower Miocene transgression nor erosion were driven by sea level variation. In contrast, a southeastward propagating slab tear that initiated at the latitude of the high pressure/low temperature metamorphic complex of northern New Caledonia likely generated east to west tilting of New Caledonia, subsidence along the West Coast and hence fringing reef development together with moderate erosion of older regolith. Coincidence between conglomerate deposition and hence prominent erosion that closely followed emplacement of postobduction granitoids influenced by a slab window suggests a genetic link. Therefore, it is concluded that short‐lived lower Miocene erosion was due to slab breakoff and subsequent uplift that occurred at ~ 22 Ma. Lower Miocene erosion profoundly dissected the Peridotite Nappe and in the northern half of New Caledonia only left isolated klippes along the West Coast. Key Points The Lower Miocene erosion was due to uplift subsequent to slab break‐offThe erosion of regolith and the Népoui conglomerate are influenced by upliftThe Népoui conglomerate is interpreted differently from previous authors
ISSN:0278-7407
1944-9194
DOI:10.1002/2014TC003588