Selenosis in north-western Queensland associated with a marine Cretaceous formation

Abstract

Selenosis in north-western Queensland was shown to be associated with the Tambo Formation of Cretaceous marine clay limestone shales.
This association was studied as a 3-stage programme. Stage 1 was a detailed investigation in a restricted 70-ac area. Stage 2 was an examination of adjacent areas. Stage 3 was a broad observational traverse of the northern portion of the incriminated Formation.
A highly selenized "poison strip" within a 70-ac enclosure was located on an extensive outcrop of the Tambo Formation. Disorders in livestock were associated with recent intensification of land use. The resultant redistribution of selenium-bearing soils made only a minor contribution to the increased toxicity of the whole enclosure. Cultivation for pasture improvement was the major contributor by encouraging the spread of both introduced and native selenium-accumulating plants to formerly barren but highly seleniferous localities. Neptunia amplexicaulis and Acacia cana were shown to be major selenium-accumulating species.
Despite other large areas of exposed seneliferous outcrops in this locality and significant selenium levels in almost every specimen, whether of rock, soil, plant or animal origin, disorders of livestock attributable to selenium excess were rare, outside the "poison strip", and of a most moderate nature.
Seleniferous outcrops of the underlying Formation were found at intervals throughout a 200-mile traverse but were extensive only in the Hughenden-Richmond area. Overlying soils representing vast areas of open grasslands were shown to be selenium-bearing. Under extensive grazing management no known endemic disorders occur that could be attributed to a dietary excess of selenium.