Structural and kinematic history of the southeast margin of the Puna Plateau, northwest Argentina
The Altiplano-Puna of the central Andes -- 1500 km long, 250 km wide, and 4000 m high -- is one of the great continental plateaus of the world. The SE margin of the Puna over lies the shoaling of the subducted Nazca Plate and, because of its dynamic morphology and its superb exposures, illustrates the relations between structural shortening and plateau uplift. The authors mapped the relations between Upper Miocene-Recent strata and major faults along a --150 km long, NE-trending segment of the Plateau boundary between 28/sup 0/-26/sup 0/30' S latitude and used analysis of slip data from >400 minor faults to determine the kinematic evolution of the region. Deformation along this margin of the Puna occurred in two phases: 1) Between 10(.) Ma and <3.5 Ma, Ordovician granitoids were thrust over Tertiary strata on NE-striking faults, dipping 15/sup 0/-55/sup 0/NW. The NW-SE shortening and vertical extension produced the presently-observed morphologic edge of the Plateau. A widespread Lower Quaternary(.) boulder conglomerate unconformably overlies these rocks and structures, indicating the culmination and end of this earlier phase. 2) The boulder conglomerate was subsequently deformed by a diverse array of reverse faults, oblique-slip and dip-slip normal faults, and strike-slip faults; the geometric variation may be due to reactivation of basement foliation or of pre-conglomerate thrusts. Apparently, structures associated with continued uplift of the Puna have moved out of the region indicating that the morphologic boundary of the Puna may eventually migrate also. If the Plateau is related to a particular subduction geometry, then structural data may also indirectly record a lateral migration of subduction segments.
- Research Organization:
- Cornell Univ., Ithaca, NY (USA)
- OSTI ID:
- 7052175
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Vol. 17; Conference: 98. annual meeting of the Geological Society of America, Orlando, FL, USA, 28 Oct 1985
- Country of Publication:
- United States
- Language:
- English
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