A magnetotelluric survey in the northern Bolivian Altiplano

Journal Article · Fri Mar 01 00:00:00 EST 1991 · Geophysical Research Letters (American Geophysical Union); (United States)

DOI:https://doi.org/10.1029/91GL00518· OSTI ID:5399922

Ritz, M ^[1]; Bondoux, F ^[2]; Herail, G; Sempere, T ^[3]

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1. ORSTOM, Dakar (Senegal)
2. ORSTOM, Port Vila (Vanuatu)
3. ORSTOM, La Paz (Bolivia)

Magnetotelluric (MT) measurements were performed at 9 sites on the northern Bolivian Altiplano in an attempt to determine thicknesses of the Cainozoic sedimentary infill and to characterize the underlying crust. At some of the sites the MT soundings show complications due to static shift effects caused by local, surficial heterogeneities. Preliminary one-dimensional (1D) modeling of the data based on the impedance tensor determinant parameters was undertaken for sites considered to be free of static effects, and was followed by 2D modeling. The model obtained indicates, from the surface downward, three important geoelectrical units, namely (1) a very low-resistivity layer (1-6 ohm-m) consisting of late Cainozoic volcanic rocks and/or Tertiary-Cretaceous sedimentary rocks 1-4 km in thickness, (2) a crustal resistive zone (about 200 ohm-m), and (3) a lower crustal or uppermost mantle conductor (less than 10 ohm-m) at depths of 40-45 km which might be related to partial melting. This model is consistent with the geological model according to which the Altiplano formed as a synorogenic basin showing abrupt changes in depositional thicknesses across thrust faults.

• OSTI ID: 5399922
• Journal Information: Geophysical Research Letters (American Geophysical Union); (United States), Vol. 18:3; ISSN 0094-8276
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
BOLIVIA
GEOLOGIC FORMATIONS
MAGNETOTELLURIC SURVEYS
ANDES
CENOZOIC ERA
CONTINENTAL CRUST
CRETACEOUS PERIOD
DEPOSITION
DEPTH
ELECTRIC CONDUCTIVITY
GEOLOGIC MODELS
GEOLOGIC STRATA
ONE-DIMENSIONAL CALCULATIONS
SEDIMENTS
STRATIGRAPHY
TERTIARY PERIOD
THICKNESS
TWO-DIMENSIONAL CALCULATIONS
DEVELOPING COUNTRIES
DIMENSIONS
EARTH CRUST
ELECTRICAL PROPERTIES
ELECTRICAL SURVEYS
ELECTROMAGNETIC SURVEYS
GEOLOGIC AGES
GEOLOGIC STRUCTURES
GEOLOGY
GEOPHYSICAL SURVEYS
LATIN AMERICA
MESOZOIC ERA
MOUNTAINS
PHYSICAL PROPERTIES
SOUTH AMERICA
SURVEYS
580000* - Geosciences