摘要:

The New Guinea Trench is a sparsely surveyed seafloor depression which runs parallel to the north coast of New Guinea for a distance of some 700 km. Its western end lies about 600 km east of the Philippine Trench; the intervening region is occupied by a complex series of north trending ridges and troughs, of which the Ayu Trough and the Tobi and Mapia ridges are the most prominent. It has been suggested and is now widely accepted that the trench marks a site of subduction, but the degree of present‐day activity is disputed. The western termination has recently been defined by combined single‐channel seismic and long range sidescan sonar surveys as lying at the ridge system which culminates in Mapia Island. The trench contains as much as 1 km of flat‐lying undisturbed sediments within the area surveyed, and the southern slopes are extensively channeled, suggesting a lack of recent deformation. The same survey has also shown that for a distance of some 400 km west of the western end of the trench, the north coast of New Guinea is flanked, at a distance of only a few tens of kilometers, by a deep trough. The sonar imagery of this “Manokwari Trough” suggests recent convergence as well as transcurrent movement. Both the existence of this trough and the abrupt termination of the New Guinea Trench are consequences of the seafloor spreading which took place in the Ayu Trough after subduction had ceased at t

ISSN:0278-7407    

DOI:10.1029/91TC01257

年代:1992

数据来源: WILEY

摘要:

Conventional thermobarometry and Gibbs' Method modeling have been used to obtain new information pertaining to the Mesozoic‐Tertiary thermal evolution of the Ruby Mountains‐East Humboldt Range and Wood Hills metamorphic complexes, northeastern Nevada. Kyanite‐grade assemblages from Clover Hill, in the extreme northeastern part of the East Humboldt Range, were produced at temperatures of 780–810 K and depths in excess of 35 km; previously published geochronologic data suggest an Early Cretaceous or Late Jurassic age for this event. The Clover Hill area subsequently experienced a major unroofing interval prior to Late Cretaceous time, during which it was brought roughly 20 km closer to the surface. The lack of stratigraphic evidence for substantial Cretaceous erosion in the region and the topology of the pressure‐temperature paths for the Clover Hill samples suggest that the unroofing mechanism may have been tectonic denudation related to the relaxation of large topographic gradients produced by crustal thickening in the hinterland of the Sevier orogen. Metamorphic rocks at Clover Hill and within the Wood Hills core complex equilibrated at 820–900 K and 500–640 MPa (18–24 km) in Cretaceous time, prior to 115 Ma. Other parts of the Ruby Mountains‐East Humboldt Range metamorphic complex, presently structurally separated from the Clover Hill sequence, were intruded extensively by Late Cretaceous granitic magmas and attained substantially higher temperatures than the Clover Hill‐Wood Hills block. Sillimanite‐grade assemblages from these areas apparently underwent roughly 10 km of unroofing and 130 K of cooling prior to final equilibration at 820–920 K and 360–430 MPa (13–16 km)

ISSN:0278-7407    

DOI:10.1029/91TC01879

年代:1992

数据来源: WILEY

摘要:

Fault and fold patterns in sedimentary rocks have been modeled using a computer code based on the distinct element method (DEM). This numerical method considers the relative motion of disconnected elastic elements governed by Newton's laws and frictional sliding criteria. Forces are transmitted between elements at contact points. By changing element size ratios, assemblages of elements can simulate different kinematic behavior from localized faulting to distributed flow. As an application of the method, we investigate folding and faulting patterns that develop in the sedimentary overburden above basement normal faults. The number, position, orientation, and sense of slip on faults as well as the fold geometry depend on the basement fault dip and basement rotation. The DEM model results have practical implications for predicting the evolving characteristics of structural traps and their petroleum potential.

ISSN:0278-7407    

DOI:10.1029/91TC02462

年代:1992

数据来源: WILEY

ISSN:0278-7407    

DOI:10.1029/92TC00001

年代:1992

数据来源: WILEY