Sedimentation of the Lower-Middle Devonian Tamworth Group, Northeastern New South Wales, Australia: A Synthesis
Titel:
Sedimentation of the Lower-Middle Devonian Tamworth Group, Northeastern New South Wales, Australia: A Synthesis
Auteur:
Ellenor, D. W.
Verschenen in:
Australian journal of earth sciences
Paginering:
Jaargang 22 (1975) nr. 3 pagina's 311-325
Jaar:
1975
Inhoud:
In contrast to recent interpretations it is here argued that the 2400+ m Lower-Middle Devonian Tamworth Group accumulated primarily in a slowly subsiding, open marine sublittoral (shelf) environment, near the western margin of the New England Geosyncline. Shallow marine or even terrestrial red arenites and breccias with concomitant spilitic intrusions characterize the lower Tamworth Group. Denudation of the southwesterly source area and relative sea level rise resulting in quiet marine conditions are suggested by the siliceous siltstones that conformably overlie the shallow marine sequence. Pebble conglomerates and arenites rest abruptly on the banded siltstones, indicating rejuvenation of the source area, and an accompanying fall in sea level. In situ coralline limestone lenses further indicate that part of the middle Tamworth Group was deposited in the photic zone. The upper Tamworth Group—banded siltstones, arenites, and bioclastic carbonate buildups—was deposited in a generally quiet sea, into which sand-size detritus was transported by gravity displacement. Where thick, though laterally impersistent, nrenites are prevalent, carbonate buildups are absent, reflecting the inhibiting effect the high terrigenous influx had on carbonate sedimentation.
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