Abstract

Metre-scale cyclicity is uncommon in siliciclastic sediments, unlike in carbonates. Fischer plots of shallow subtidal to intertidal siliciclastic cycles of Proterozoic age from Australia reveal systematic thickening and thinning patterns that, after correcting for tectonic subsidence, loading, and compaction, are compatible with a eustatic origin. Both 1.5 m.y. and 0.25-0.50 m.y. period sea-level changes are recognizable; the longer-period curves are asymmetric and indicate rapid rises followed by slow falls in sea level. Predictable facies and grain-size trends are associated with different slopes on the longer-period curve. Fischer plots provide an appropriate method for recognizing ecstatic effects in siliciclastic sediments that are less sensitive to sea-level changes than carbonates.

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