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Constraints on the vertical motion of eastern Australia during the Mesozoic
Author(s) -
Gallagher KERRY,
Dumitru TREVOR A.,
Gleadow ANDREW J. W.
Publication year - 1994
Publication title -
basin research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.522
H-Index - 83
eISSN - 1365-2117
pISSN - 0950-091X
DOI - 10.1111/j.1365-2117.1994.tb00077.x
Subject(s) - geology , cretaceous , fission track dating , detritus , mesozoic , subsidence , paleontology , structural basin , sedimentary rock , geomorphology , geochemistry , tectonics
Backstripping and apatite fission track analysis are used to constrain the Mesozoic vertical motion of the eastern Australian basins (Eromanga, Surat and Clarence‐Moreton). The backstripping results show that subsidence was linear during the Jurassic, and the rate of subsidence shows an overall increase (by a factor of about 2) towards the eastern margin. The Cretaceous section is well preserved only in the Eromanga Basin, and the backstripping results show that the apparent subsidence rate increased by a factor of 5–10 during the Early Cretaceous. The sediments show a lithological cyclicity which is the result of a variable influx of volcanogenic detritus from the convergent eastern margin. The rapid Cretaceous subsidence corresponds to a large influx of this volcanogenic material, resulting in progressively non‐marine deposition at a time when global sea‐level was rising. The apatite fission track data suggest that the Cretaceous section was probably deposited over the Surat and Clarence‐Moreton Basins but has since been eroded off. The exhumation‐induced cooling may have commenced earlier in the eastern region (Late Cretaceous to Early Tertiary) and slightly later to the west (Early to Middle Tertiary). Furthermore, the inferred total amount of removed section is greater (˜2.5 km) in the east than in the west (<1 km). The present‐day thermal regime in the Eromanga Basin is considered to be a relatively recent (<10Ma) phenomenon, as non‐zero fission track ages are maintained in sediments currently at temperatures of ˜120°C. Overall, the regional backstripping and apatite fission track results support a model of platform tilting, This is related to the inferred subduction along a convergent margin on eastern Australia during the Jurassic to Early Cretaceous. The cessation of subduction, and subsequent opening of the Tasman Sea in the Late Cretaceous, was accompanied by uplift on the eastern margin and the termination of widespread deposition on the platform.