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A drastic lower Miocene regolith evolution triggered by post obduction slab break‐off and uplift in New Caledonia
Author(s) -
Sevin Brice,
Cluzel Dominique,
Maurizot Pierre,
RicordelProg Caroline,
Chaproniere George,
Folcher Nicolas,
Quesnel Florence
Publication year - 2014
Publication title -
tectonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.465
H-Index - 134
eISSN - 1944-9194
pISSN - 0278-7407
DOI - 10.1002/2014tc003588
Subject(s) - geology , marine transgression , conglomerate , paleontology , late miocene , moraine , neogene , middle miocene disruption , peridotite , obduction , geomorphology , oceanic crust , subduction , glacial period , sedimentary rock , mantle (geology) , tectonics , structural basin
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.