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| Titel |
Sea level reconstructions and non-marine sedimentation at the Triassic-Jurassic boundary: southwestern margin of the Neotethys in the Salt Range, Pakistan |
| VerfasserIn |
Shahid Iqbal, Michael Wagreich |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250122261
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| Publikation (Nr.) |
 EGU/EGU2016-1249.pdf |
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| Zusammenfassung |
| The environmental changes during the Triassic-Jurassic boundary interval and the associated
mass extinction event are still strongly debated. Sea-level reconstruction records during this
interval reveal an end-Triassic global regression event. Erosion and karstification at the top of
Triassic sediments, and Lower Jurassic fluvial channels with reworked Triassic clasts
indicate widespread regression in the European basins. Laterite at the top of the
Triassic, and quartzose conglomerates/sandstones at the base of the Jurassic indicate a
fluvial/terrestrial onset in Iran and Afghanistan. Abrupt emergence, erosion and facies
dislocation, from the Triassic dolomites (Kingriali Formation) to Lower Jurassic
fluvial/continental quartzose conglomerates/pebbly sandstones (Datta Formation) occur in the
Tethyan Salt Range of Pakistan. Sedimentological analyses indicate marine regression
and emergence under tropical-subtropical conditions (Greenhouse conditions) and
negates the possibility of glacial influence in this region. Field evidences indicate the
presence of an undulatory surface at the base of the Jurassic and a high (Sargodha
High) is present south of the Salt Range Thrust, the southern boundary of the basin.
Furthermore, geophysical data (mostly seismic sections) in different parts of the basin
display normal faults in the basement. These features are interpreted as horst and
graben structures at the Triassic-Jurassic boundary in the Kohat-Potwar Plateau.
The Lower Jurassic Datta Formation appears to have been deposited in an overall
graben fill settings. Similar normal faults and graben fill geometries are observed on
seismic sections in Tanzania, Mozambique, Madagascar and other regions of the
southeastern margin of the African Plate and are related to the Karoo rift system. To
summarize, the basement normal faults and the graben fill features at the Triassic-Jurassic
boundary in the Kohat-Potwar Plateau can be correlated to similar features common
in the Karoo rift area. Regional sea-level fall associated with this rift produced
erosional and reworking features similar to those occur at the Triassic-Jurassic
boundary in the European basins, Iran and Afghanistan. The tectonic correlation
with the European basins and sedimentological evidences for the globally present
Jurassic-Triassic boundary in the Salt Range of Pakistan encourage a detail work in this
regard. |
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