Puna: a source region for the Pampean loess

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

OSTI ID:6593476

Bloom, A L; Strecker, M R; Scoppa, C

The Quaternary Pampean loess of NE Argentina has the same texture and grain-size distribution as northern hemisphere loess, but a very different mineral composition. Unweathered calcic and intermediate plagioclase is the most abundant mineral in the sand fraction followed by quartz, orthoclase, volcanic glass, and fragments of volcanic rock. Glass shards make up more than one-half of the silt fraction in most samples, but their abundance is highly variable. Grain size increases toward the west and southwest, primarily by an increase in the proportion of sand. Most authorities infer a polygenetic source for the Pampean loess. Andean volcanoes and the Patagonian plains to the west and southwest are commonly mentioned, but there are almost no Quaternary volcanoes in the Andes between 28/sup 0/ and 34/sup 0/ S latitude, directly west of the main Pampean loess region. A previously unconsidered, mineralogically appropriate, and currently active source for the silt fraction of the Pampean loess is the Puna, the high plateau in NW Argentina where volcanism has been active throughout the late Cenozoic Era. Shuttle astronauts in September 1983 photographed streamers of dust blowing SE out of desert basins in the Puna, originating more than 3700 m above sea level. The dust was clearly visible above low clouds that covered the Pampas at the time, where surface winds were light and variable. Wind streaks and yardangs prove that eolian erosion is active in the Puna.

• Research Organization: Cornell Univ., Ithaca, NY (USA)
• OSTI ID: 6593476
• 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

Related Subjects

58 GEOSCIENCES
ARGENTINA
SOILS
GRAIN SIZE
MINERALOGY
TEXTURE
ANORTHOSITES
CALCITE
EROSION
QUARTZ
QUATERNARY PERIOD
VOLCANIC REGIONS
VOLCANISM
VOLCANOES
WIND
ALKALINE EARTH METAL COMPOUNDS
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATES
CENOZOIC ERA
CHALCOGENIDES
CRYSTAL STRUCTURE
DEVELOPING COUNTRIES
GABBROS
GEOLOGIC AGES
IGNEOUS ROCKS
LATIN AMERICA
MICROSTRUCTURE
MINERALS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PLUTONIC ROCKS
ROCKS
SILICON COMPOUNDS
SILICON OXIDES
SIZE
SOUTH AMERICA
580300* - Mineralogy
Petrology
& Rock Mechanics- (-1989)
580100 - Geology & Hydrology- (-1989)