New evidence for mid-Pliocene-early Pleistocene glaciation in the northern Patagonian Andes Argentina

Conference · Tue Jan 01 00:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6323076

Stephens, G C; Evenson, E B; Rabassa, J

Mount Tronador is an extinct, glacially eroded strato-volcano located in the northern Patagonian Andes. With a summit elevation of 3556 m, Mount Tronador lies mostly above the present regional snowline (2000 m) and is largely covered by extensive snow fields and glaciers. The rocks of Mount Tronador comprise the Tronador Formation, a 2000 m thick sequence of interlayered basalts, andesites, ignimbrites, agglomerates, volcanic mudflows and lahars. This volcanic edifice is built on an erosional land surface of Tertiary age. Three K-Ar dates from the Tronador Formation yield radiometric ages of 3.2, 0.34 and 0.18 m.y. Striated clasts have been found included in several large glacial boulders derived from volcanic mudflows and lahars of the Tronador Fm. These boulders have been eroded by the Rio Manso Glacier and deposited in its Neoglacial moraines. The lahar boulders themselves contain pebbles and boulders of andesitic rocks in a vitroclastic matrix of pyroclastic origin. The striated clasts are well-rounded, shaped and polished, and the striations can be traced beneath the volcanic matrix. Thus these striated clasts represent a pre-Holocene cycle of glaciation. Mercer (1976) and Ciesielski (1982) document glaciations from southern Patagonia (2.1-3.5 m.y.) and from the southwestern Atlantic (2.1-3.9 m.y.) respectively. The discovery of striated clasts in lahars and mudflows of the Tronador Fm. indicates the existence of a heretofore undocumented Pliocene-Pleistocene glaciation in northern Patagonia.

• Research Organization: George Washington Univ., Washington, DC (USA)
• OSTI ID: 6323076
• Report Number(s): CONF-8510489-
• Journal Information: Geol. Soc. Am., Abstr. Programs; (United States), Vol. 36; Conference: 98. annual meeting of the Geological Society of America, Orlando, FL, USA, 28 Oct 1985
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
ARGENTINA
PALEOCLIMATOLOGY
VOLCANOES
VOLCANIC ROCKS
ISOTOPE DATING
ARGON ISOTOPES
GEOLOGIC FORMATIONS
GEOMORPHOLOGY
GLACIERS
MORAINES
PLEISTOCENE EPOCH
PLIOCENE EPOCH
POTASSIUM ISOTOPES
AGE ESTIMATION
ALKALI METAL ISOTOPES
CENOZOIC ERA
DEVELOPING COUNTRIES
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGY
IGNEOUS ROCKS
ISOTOPES
LATIN AMERICA
PALEONTOLOGY
QUATERNARY PERIOD
ROCKS
SOUTH AMERICA
TERTIARY PERIOD
580100* - Geology & Hydrology- (-1989)