obduction

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obduction

[əbduk′shən]
Etymology: L, obductio, a covering
a forensic medical autopsy.
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These paleomagnetic data involve a rather unrealistic scenario: a 1000 km northward migration of the obducted ophiolite with its Upper Cretaceous "cover.
This model is preferred to one that involves widespread uplift of the Gander margin and removal by erosion of the uppermost strata of the Miramichi Group (plus any or most obducted Penobscot Arc rocks).
Erosion of a possibly uplifted Gander margin during the Tremadoc-early Arenig may have removed extensive Miramichi strata and obducted arc before deposition of the middle to late Arenig conglomerate and volcanic rocks of the Napadogan and Lunksoos areas.
The volcanic clasts and detritus in these two localities may have been derived from three possible sources: from volcanic rocks intercalated in the upper layers of the Miramichi-Grand Pitch strata (a possible local source only, given the general absence of such volcanic rocks in present-day strata, but probably not in these two localities); from obducted Penobscot Arc rocks lying structurally above the Miramichi-Grand Pitch strata (quite plausible but the age and tectonic setting of the volcanic clasts must be determined by isotopic and geochemical analyses); and from hypothetical volcanic rocks formed along the rifts and essentially the same age as the conglomerate (theoretically possible but judged improbable because volcanic strata are lacking in the conglomerate units).
The lack of volcanic clasts suggests that possible obducted Penobscot rocks were removed by erosion before deposition of the quartz sandstone gravel, or they did not exist in the vicinity.
The ultrabasic-basic rocks of the Vizcaino Peninsula, above the so-called Puerto Nuevo melange, had been considered as a single obducted slab of an Upper Triassic oceanic lithosphere and that so-called melange of Puerto Nuevo as a Lower Cretaceous unit of Franciscan affinity (Rangin, 1977).
1995) and it also suggests that other similar ultrabasicbasic occurrences, axiomatically related to a rifting, and therefore considered as obducted oceanic lithosphere, could be in reality autochtonous bodies, generated by a magma underplating of the crust of an active margin.
2003) required for the Myanmar continental margin obducted over the western half of the IMR basin.
The ophiolite was intially obducted at 90 Ma within an intraoceanic setting (Gnos et al.
1998) supported the idea that it is an obducted island arc turned on end during the Himalayan orogeny.
The Kohistan sequence: Crust and mantle of an obducted island arc.
Petrology of the obducted mafic and ultramafic metamorphites from the southern part of the Kohistan island arc sequence.