 |
| Titel |
The extension discrepancy at rifted margins - evidence for a complex structural evolution |
| VerfasserIn |
T. Reston, K. McDermott |
| Konferenz |
EGU General Assembly 2009
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250026705
|
|
|
|
|
|
| Zusammenfassung |
| Across rifted margins, the prerift continental crust thins from ~ 30 km, reaching zero at the
continent-ocean transition (COT) beyond which either oceanic crust or unroofed mantle
forms top basement. However at most margins, the amount of extension measured from fault
geometries (βf typically < 1.25) is far less than that required to explain whole crustal and
lithospheric thinning, deduced from crustal thickness (whole crustal βc tending to -) and
subsidence. This is the extension discrepancy. The two end-member explanations are crustal
depth-dependent stretching (DDS) and unrecognised faulting. There are several problems in
explaining the extension discrepancy through DDS. First, excess thinning of the
lower 80% of the crust should somewhere be balanced by thickening of the same or
by excess thinning of the upper 20%. Neither is observed. Second, the seismic
velocity structure of conjugate margins provides no evidence for significant crustal
DDS. Finally, lower crustal rocks are present (i.e. not removed by DDS) at the
only deep margin where basement has been sufficiently sampled. An alternative
explanation for the extension discrepancy is that not all the extensional faulting has been
recognized (βf |
|
|
|
|
|
|