Rain and dry deposition were sampled together for 28-day periods throughout 1974-75 at 27 stations, all but three being in the Murray-Darling Drainage Division (1.06 x 106 km2). Samples were analysed for calcium, magnesium, potassium, sodium, chloride and sulfate. Similar procedures continued during 1975-77 for six stations used previously and a new one. Rainfall records and the mean ionic concentrations, including estimates of HCO3 + NO3, indicate that the mean aggregate concentration for eight ions in 1974-75 ranges from 3 to 35 mgL-1 for 24 stations in the drainage division and from 14 to 23 mgL-1 for three stations near the South Australian coast. Higher concentrations in the drainage division refer principally to stations in a semi-arid district and are associated with relative abundance of calcium and HCO3 derived from the calcareous soils there. Terrestrial and oceanic sources of the ions are considered. Oceanic input of chloride is estimated using mean annual concentrations to give a maximum value and concentrations for the most rainy periods to give a minimum value. These estimates are compared with discharge of chloride by the Murray and Darling Rivers, with the conclusion that in 1974-75 the oceanic input of chloride to the Darling catchment was mostly retained there, but amounts equal to the accessions to the Murray catchment were probably all flushed out. Details are given in an appendix of NO3 concentrations determined by others at two stations in frequent samples of rain.

No abstract

The problems inherent in the conversion of stacking velocities to true vertical velocities have been studied by nonzero offset raypath tracing of primary P‐waves through a suite of varied geologic sections. It is shown that conversion errors can be caused by timing errors as a result of migration and also by raypath distortions due to complex overburdens. The raypath modeling shows that (1) the customary assumption that stacking velocities approximate root‐mean‐square velocities is erroneous in areas of geologic complexity. (2) Essential velocity information from horizons overlain by geologic irregularities is often difficult to recognize and is apt to be ignored or misidentified. (3) Standard fitting of hyperbolic curves to produce normal moveout traces is erroneous in areas of geologic complexity. Consequently there is a need for correct migration, which takes into account all overburden complexities, of all traces in a common‐depth‐point gather prior to velocity determination so that realistic velocities can be obtained.

Profiles from mound and depression at two apparently comparable gilgai sites provided samples for 82 radiocarbon measurements and other studies of profile variation, including micromorphology and swelling capacity. Comparable trends of apparent mean residence time (AMRT) of soil humus with depth were found for both profiles at Miram, with gradual increase to approximately 8500 years at 2 m. This contrasts with results for Lillimur, where the maximum AMRT for the mound profile is almost 6000 years but that for the depression profile is only 2000 years. Interpretation of the AMRT values is complicated by evidence of layering and the probability of a buried soil at each site. Downward movement of soil is shown by micromorphological features and by AMRT values taken in conjunction with evidence of layering. Evidence was sought on churning with a marked lateral component and on fossil gilgai, but without firm conclusions. It is probable that at both sites gilgai formation involved the upward movement of the mass of soils constituting the mound, at a time when it still retained relatively sandy top soil. Leaching of carbonate may have increased the microrelief.

Difficulties in using granulometry to characterize the non-clay fraction of the presumed aeolian sediments known as parna are considered by reference to the results of repeated analyses of samples. Incomplete dispersion of clap accounted for different results with two samples, one being from material identified as subplastic. Bimodal size frequency distributions were detected for several samples, a condition which should invalidate modal diameter as the measure of average grain size. Mean diameter is regarded as an appropriate measure for the samples. The more accurate results obtained for the samples do not upset the earlier conclusions regarding distribution of Widgelli parna, but they suggest an important distinction between the western and eastern samples of the material. Suggestions are made concerning determination of particle size for parna samples.