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Table of Contents - Special Paper 400

Collisional Delamination in New Guinea: The Geotectonics of Subducting Slab Breakoff

by Mark Cloos, Benyamin Sapiie, Andrew Quarles van Ufford, Richard J. Weiland, Paul Q. Warren, and Timothy P. McMahon

Abstract		1
Chapter 1. Geology of the Central Range of Western New Guinea
Introduction		3
Geology of Western New Guinea		4
	Geologic Framework	4
	Cenozoic Plate-Tectonic Setting	4
	Active Tectonism	4
Magmatism in the Highlands		7
New Guinea Trench — A Reactivating Relict		9
Geologic Transect — Western Central Range		10
	Foreland Basin — Buried Continental Shelf	10
	Foothills — Leading Edge of Central Range Orogenic Belt	13
	Mapenduma Anticline — Thick-Skinned Deformation	13
	Folds in the Southern Central Range — Thin-Skinned Deformation	14
	Ruffaer Metamorphic Belt — Metamorphosed Passive Margin Strata	16
	Irian Ophiolite Belt — Accreted Oceanic Lithosphere	16
Shortening Estimates and Plate-Tectonic Rates		17
Chapter 2. Mechanics of Subducting Slab Breakoff by Collisional Delamination
Lithospheric Delamination		19
Rupture of the Lithosphere		20
	Fracture and Flow	20
	Plastic and Viscous Flow	21
	The Lithosphere: Brittle/Plastic Behavior	22
	The Asthenosphere: Viscous Response	22
Peak Strength in the Crust and Mantle		23
Force Transmission		24
Plate Bending during Subduction		25
Buoyancy of the Lithosphere		26
Chapter 3. Palinspastic Reconstruction of Collisional Delamination in New Guinea
Collisional Delamination — Scaled Cross Sections		29
	25 Ma: Intraoceanic Subduction	31
	15 Ma: Emergence of Isolated Islands	32
	12 Ma: Beginning of the Central Range Orogeny	33
	10 Ma: Thin-Skinned Deformation	34
	8 Ma: Collisional Delamination Begins	35
	6 Ma: Thick-Skinned Deformation and Magmatism	37
	4 Ma: Collisional Delamination Is Complete	37
	2 Ma: Postcollision	39
	Present Day	40
Collisional Delamination and Induced Magmatism		40
Collisional Delamination and Sedimentation		42
Time-Transgressive Orogenesis: Propagating Tear		42
Along-Strike Variations in Structural Style		44
Lithospheric Healing after Delamination		45
Plate Tectonic Changes Related to the Collision Forming New Guinea: Nearby and Transoceanic		45
Conclusions		46
Acknowledgments		46
References Cited		46