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Tectonics in central Papua and the adjoining part of New Guinea.

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Pitt, Rodney Philip Brown 1966 , 'Tectonics in central Papua and the adjoining part of New Guinea.', PhD thesis, University of Tasmania.

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Abstract

Detailed stratigraphic and structural analysis has shown that
tectonic development in the central Papua region can be divided into
three stages.

The first stage involved apparent eastward migration of zones
of deformation and sedimentation from the Palaeozoic to the late
Mesozoic. Pre-Permian, late Palaeozoic to Triassic, and mainly ?Jurassic
sediments were thickly deposited in three adjacent belts, with the east-
ern ?Jurassic belt probably formed on a floor composed of the rocks now
uplifted and exposed in parts of the Papuan Basic-Ultrabasic Belt.
Sedimentation may have been controlled by subsidence caused by crustal
tension. This eastwards, sedimentary prograding towards an oceanic
province was punctuated by phases of deformation and metamorphism before
the Permian, in the late Triassic, and in the early Cretaceous, each
event being restricted to the wedge of sediment built up just prior to
the deformation. The axial parts of the pre-Permian and late Triassic
belts of deformation are reflected in the trends of the Erave-Wana Swell
and the "Bismarck-Moresby high" respectively. Early Cretaceous deform-
ation included the initial westerly downthrow of the Owen Stanley Fault,
which is the western boundary of the Papuan Basic-Ultrabasic Belt.

The second stage involved westward migration of zones of late
Mesozoic to Middle Miocene deformation and sedimentation across a base-
ment of rocks formed and deformed during the first stage. Cretaceous,
Eocene, early and late Lower Miocene and Middle Miocene deep-water
marine sediments were thickly deposited in five adjacent belts parallel
to and west of the Owen Stanley Fault, each belt overlapping the western
margin of the preceding one. The sediments were affected by periodic
folding and uplift along trends parallel to the Owen Stanley Fault.
The most intense deformation during any one phase occurred within the
sedimentary belt formed just before the deformation. Thus, fold belts
which were the provenance of the deep-water sediments and troughs in
which they accumulated were closely related in space and time.
Migration in the late Cretaceous and in the late Palaeogene was caused
by periodic crustal compression accompanied by metamorphism. Further
westward migration was due to phases of compression, or to vertical
oscillation of crustal blocks with folding produced by surficial
gravity spreading.

The third stage involved Middle Miocene to Recent deformations
and zones of sedimentation trending NNW to west, both of which were
superimposed on; but mainly oblique to, the older tectonic features.
The broad anticline and syncline-like warpings of the Eastern Cordillera,
the Ramu-Markham Depression (an area of Pliocene to Quaternary sediment
ation) and the Lakekamu Embayment (Upper Miocene to Quaternary sediment
ation) were probably produced by compressive forces directed NE-SW.
WNW-trending sinistral transcurrent faults were also moving from the
Middle Miocene to the Recent and may have been caused by the same com-
pressive forces. Since there is also evidence of anticlockwise crustal
rotations in the area, the stress field may have involved an overall
sinistral shear couple acting about a vertically oriented intermediate
principal stress. Some of the Pleistocene folds in the Lakekamu
Embayment could have developed through gravity sliding of rocks off the
SW flank of the rising Eastern Cordillera.

Item Type: Thesis - PhD
Authors/Creators:Pitt, Rodney Philip Brown
Keywords: Geology, Structural, Geology
Copyright Holders: The Author
Copyright Information:

Copyright 1966 the author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (Ph.D.) - University of Tasmania, 1967. Includes bibliography

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