Transcript geo-4840 tectonics-s04

GEO-4840 TECTONICS-S05
PART 1:
LECTURES [Wed 12-14 (16)]
19/1 - 09/3
PART 2:
STUDENT PROJECTS [Presentations]
PART 3:
FIELD TEACHING [Corsica]
PART 4:
FIELD REPORTS
PART 5:
EVALUATION [PROJECTS, REPORTS & EXAM]
13/4
end April
[Hand in]
11/5
14/6
GEO-4840 TECTONICS-S05
LECTURES:
Introduction and course content; Anatomy and tectonic processes
in mountain belts.
Main themes:
1) Material balance and properties
Uplift and subsidence.
Topography, crustal and lithospheric thicknesses/structure
2) Wilson cycle tectonics,
Ocean-continent transition,
Oceanic complexes, exotic terranes.
Ophiolite obduction, (Oman, Caledonian and Appalachian).
Andean margins,
Incipient continental collision, Australia - Banda Arc collision.
Continental collision
LECTURES (continued):
3) Examples of Continental collision zones:
The Himalayan-Tibetan region
The Caledonides, with emphasis on Scandinavia
Mediterranean
4) From collision to extension,
Dynamics of orogenic wedges,
Exhumation,
Renewed rifting.
Student projects (written and oral presentation):
All projects are related to the field-course/work/excursions.
The student seminar day will be Wed. 13. April
1) The Herzynian basement of Corsica ()
2) The main tectonic units of the Alps and their correlation
with Alpine Corsica. ()
3) The structural geology of Alpine Corsica, an overview ()
4) The high-pressure metamorphism of Alpine Corsica ()
5) Exhumation of high-pressure rocks in the transect from
Corsica to the Apennines in Italy ()
6) The Alpine ophiolitic rocks of Corsica ()
7) Formation of Pseudotachylytes ()
8) Formation of Olistostromes ()
MOUNTAIN CHAINS ARE THE MOST IMPRESSIVE
VISIBLE TOPOGRAPHIC FEATURES ON THE
EARTH´S SURFACE
The anatomy of mountain belts:
The product of complex interactions of thrusting and extension
accompanied by pro- and retrograde metamorphic reactions and
erosional denudation
MOUNTAIN BELTS, OLD (at least from Mid Proterozoic) and YOUNG,
HAVE VERY SIMILAR INTERNAL STRUCTURES:
• FORELAND
• CONTINENTAL BASEMENT-CORED NAPPES
• SUTURE WITH OCEANIC AND EXOTIC TERRANES
• HINTERLAND / PLATEAU REGIONS
• FORELAND
Various
stages of
orogenic
maturity
along strike
Andean
margins
Foreland
flexure
Common
internal
structure
of orogenic
belts (in
space and time)
Suture(s)
Hinterland orogenic plateau
Foreland
basin
Schematic view of stages in a classical Wilson cycle
5) Remnant stage
Continental collision, suture zones, deformation and metamorphism, mountain building
Extensional collapse, faulting and collapse
basins
4) Terminal stage
Near closure of ocean, mature arcs and
back-arc, accreationary wedges, HP-LT
metamorphic complexes
(Mediterranean See area)
3) Vaning stage: Intra-oceanic subduction
and island arcs transition to Andean margins.
(SE Asia and Western Passific)
2) Mature stage Passive margins with large
shelf-areas (Atlantic Ocean)
1) Embryonic to Young stage.
Rifts to small ocean basin with sea-floor
spreading. (East African rift and Red Sea)
Exact estimates of material present in the orogen
Le Pichon et al., 1993
ESTIMATES OF MISSING CONTINENTAL MATERIAL
Topography and erosional levels are taken into consideration:
Dewey et al. (1986) ca 1,2 x
India
104
km2
Present continental
crust
erosion
Tarim
Le Pichon et al (1993)
Linear shortening between 1850 - 2600 km
Surface loss during the past 45 myr from 57 to 62 x 105 km2
Rate of surface loss: ≈ 1,1 x 10 km2 x 10-6yr
Arial deficit in sections ≈ 33 - 52 x 105 km2 (max)
18 - 30 x 105 km2 (min)
(Depends on estimates of original surface elevation)
WHAT IS THE EXPLANATIONS FOR THE DEFICIT?
1) LATERAL TRANSPORT OF MATERIAL
The lateral extrusion model
For SE Asia
Tapponnier et al., 1982, 1986
Fournier
Jolivet et al.
2) VERTICAL TRANSPORT OF MATERIAL
(SUBDUCTION / EDUCTION)