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Subsidence, sedimentation and sea‐level changes in the Eromanga Basin, Australia
Author(s) -
Gallagher KERRY,
Lambeck KURT
Publication year - 1989
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.1365-2117.1989.tb00030.x
Subject(s) - geology , cretaceous , sedimentary depositional environment , structural basin , subsidence , tectonic subsidence , paleontology , sedimentary rock , tectonics , back stripping , basin modelling , fluvial , sea level , sediment , sedimentary basin , geomorphology , sedimentary basin analysis , oceanography
The Jurassic‐Cretaceous subsidence history of the Eromanga Basin, a large intracratonic sedimentary basin in central eastern Australia, has been examined using standard backstripping techniques, allowing for porosity reduction by compaction and cementation. Interpretation of the results suggests that during the Jurassic the basin was subsiding in a manner consistent with the exponentially decreasing form predicted by simple thermally based tectonic models. By the Early Cretaceous, the rate of subsidence was considerably higher than that expected from such models and nearly half of the total sediment thickness was deposited over the final 20 Myr of the basin's 95 Myr Mesozoic depositional history. The Early Cretaceous also marks the first marine incursion into the basin, consistent with global sea‐level curves. Subsequently, however, the sediments alternate between marine and non‐marine, with up to 1200 m of fluvial sediments being deposited, and this was followed by a depositional hiatus of about 50 Myr in the Late Cretaceous. This occurred at a time when global sea‐level was rising to its peak. A model is presented which is consistent with the rapid increase in tectonic subsidence rate and the transgressive‐regressive nature of the sediments. The model incorporates a sediment influx which is greater than that predicted by the thermally based tectonic models implied by the Jurassic subsidence history. The excess sedimentation results in the basin region attaining an elevation which exceeds that of the contemporary sea‐level, and thereby giving the appearance of a regression. The present day elevation of the region predicted by the model is about 100–200 m above that observed. This discrepancy may arise because the primary tectonic subsidence is better represented by a linear function of time rather than an exponentially decreasing form.