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| Titel |
Unroofing of the Gangdese arc as documented in the Cretaceous succession of the Xigaze forearc basin (South Tibet) |
| VerfasserIn |
Wei An, Xiumian Hu, Jiangang Wang, Eduardo Garzanti |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250071954
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| Zusammenfassung |
| The Xigaze forearc basin formed in the Cretaceous, between the Yalung-Zangbo
suture zone to the south and the Gangdese arc to the north, during subduction of
Neo-Tethyan oceanic lithosphere under the Lhasa terrane (Einsele et al., 1994; Durr, 1996;
Wang et al., 1999, 2012; Wu et al., 2010). Well-preserved and superbly exposed
strata provide an excellent opportunity to study the evolution of a forearc basin. The
succession includes the Sangzugang, Chongdui, Ngmaring and Padana Formations
(from bottom to top). The Sangzugang Fm. accumulated as a carbonate platform
on the southern Lhasa margin in the Aptian- Early Albian (~120-107 Ma), while
cherts of the lower Chongdui Fm. were deposited on the continental rise. In the Late
Albian- Cenomanian (~107-98 Ma), turbiditic sandstones were deposited in distal-fan
(lower-middle Chongdui sandstones) to slope settings (lower Ngmaring Fm.). The
upper Ngmaring and Padana Fms. (Late Cenomanian- Early Campanian, 98-77 Ma)
document a shallowing-upward succession deposited in submarine-fan, shelfal and
finally deltaic environments, recording the transition from the underfilled stage
(Aptian-Coniacian; ~120-86 Ma), to the filled stage (Santonian-Campanian; 86-77
Ma).
Sandstone composition evolves from feldspatho-lithic arenite to litho-feldspatho-quartzose
and finally litho-quartzose, indicating a change from undissected to dissected arc and finally
mixed provenance. Detrital zircons from the upper Chongdui and lower-middle Ngmaring
Fms. yielded dominantly Mesozoic ages, passing upward from unimodal (peak age at 110
Ma) to bimodal distribution (peak ages at ~110 and ~158 Ma). Age patterns are more
complex in the upper Ngmaring and Padana Formations, with many pre-Mesozoic ages and
more clusters of Mesozoic ages. Our dataset indicates volcanic and next plutonic rocks of the
Gangdese arc as the main source of sediments in the early forearc-basin stage. Erosion of
the Lhasa block later on attested to the final unroofing stage of the Gandese arc. |
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