 |
| Titel |
Craton Heterogeneity in the South American Lithosphere |
| VerfasserIn |
S. Lloyd, S. Van der Lee, M. Assumpcao, M. Feng, G. S. Franca |
| Konferenz |
EGU General Assembly 2012
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250070451
|
|
|
|
|
|
| Zusammenfassung |
| We investigate structure of the lithosphere beneath South America using receiver functions,
surface wave dispersion analysis, and seismic tomography. The data used include recordings
from 20 temporary broadband seismic stations deployed across eastern Brazil (BLSP02) and
from the Chile Ridge Subduction Project seismic array in southern Chile (CRSP). By jointly
inverting Moho point constraints, Rayleigh wave group velocities, and regional S and
Rayleigh wave forms we obtain a continuous map of Moho depth. The new tomographic
Moho map suggests that Moho depth and Moho relief vary slightly with age within
the Precambrian crust. Whether or not a correlation between crustal thickness and
geologic age can be derived from the pre-interpolation point constraints depends
strongly on the selected subset of receiver functions. This implies that using only
pre-interpolation point constraints (receiver functions) inadequately samples the spatial
variation in geologic age. We also invert for S velocity structure and estimate the
depth of the lithosphere–asthenosphere boundary (LAB) in Precambrian South
America. The new model reveals a relatively thin lithosphere throughout most of
Precambrian South America (< 140 km). Comparing LAB depth with lithospheric
age shows they are overall positively correlated, whereby the thickest lithosphere
occurs in the relatively small Saõ Francisco craton (200 km). However, within the
larger Amazonian craton the younger lithosphere is thicker, indicating that locally
even larger cratons are not protected from erosion or reworking of the lithosphere. |
|
|
|
|
|
|