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We discuss the evidence for frigid, strongly seasonal climates near sea level which preferentially existed in low palaeolatitudes during the Neoproterozoic. The Neoproterozoic glacialperiglacial palaeoclimate is one of the major paradoxes in contemporary earth science.

The evolution of the obliquity of the ecliptic (e), the Earth's axial tilt of 23.5°, may have greatly influenced the Earth's dynamical, climatic and biotic development. For e > 54°, climatic zonation and zonal surface winds would be reversed, low to equatorial latitudes would be glaciated in preference to high latitudes, and the global seasonal cycle would be greatly amplified. Phanerozoic palaeoclimates were essentially uniformitarian in regard to obliquity, with normal climatic zonation and zonal surface winds, circum-polar glaciation and little seasonal change in low latitudes. Milankovitch-band periodicity in early Palaeozoic evaporites impliese¯≈ 26.4 ± 2.1°at ∼ 430 Ma, suggesting that the obliquity during most of Phanerozoic time was comparable to the present value. By contrast, the paradoxical Late Proterozoic (∼ 800−600Ma) glacial environment— frigid, strongly seasonal climates, with permafrost and grounded ice-sheets near sea level preferentially in low to equatorial palaeolatitudes—implies glaciation with e > 54° (assuming a geocentric axial dipolar magnetic field). Palaeotidal data accord with a large obliquity in Late Proterozoic time. Indeed, Proterozoic palaeoclimates in general appear non-uniformitarian with respect to climatic zonation, consistent with e > 54°. The primordial Earth's obliquity is unconstrained by the widely-accepted single-giant-impact hypothesis for the origin of the Moon; an impact-induced obliquity ≳ 70° is possible, depending on the impact parameters. Subsequent evolution of e depends on the relative magnitudes of the rate of obliquity-increasee⋅t caused by tidal friction, and the rate of decrease e⋅p due to dissipative core-mantle torques during precession (e < 90° is required for precessional torques to move e toward 0°). Proterozoic palaeotidal data indicate e⋅t ≈ 0.0003−0.0006″/cy (seconds of arc per century) during most of Earth history, only half the rate estimated using the modern, large value for tidal dissipation. The value of e⋅p resulting from the combined effects of viscous, electromagnetic and topographic core-mantle torques cannot be accurately determined because of uncertainties in estimating, at present and for the geological past, the effective viscosity of the outer core, the nature of magnetic fields at the core-mantle boundary (CMB) and within the lower mantle, and the topography of the CMB. However, several estimates of e⋅p approximate, or exceed by several orders of magnitude, the indicated value of e⋅t. If e⋅p did indeed exceede⋅t in the past, then the obliquity would have decreased during Earth history. It is postulated here that the primordial Earth acquired an obliquity of ∼ 70° (54° < e < 90°) from the Moon-producing single giant impact at ∼ 4500Ma (approach velocity ≈ 5–20km/s, impactor/Earth mass-ratio ≈ 0.08−0.14). Secular decrease in e¯ subsequently occurred under the dominant influence of dissipative core-mantle torques. From 4500-650 Ma, e¯ slowly decreased to ≈ 60° (〈e⋅〉=−0.0009"/cy), e¯ then decreased relatively rapidly from ∼ 60° to ∼ 26° between 650 and 430 Ma ((〈e⋅〉=−0.0556"/cy)); climatic zonation changed from reverse to normal when e¯ ∼ 610 Ma, and 〈e˙〉 and the rate of amelioration of global seasonality were maxima for e¯= 45°at∼ 550Ma (the precessional rate Ω is maximum when e= 45°, and e⋅p varies as Ω2). Since 430 Ma, 〈e˙〉 has been ≲ −0.0025″/cy and e¯ has remained near its Quaternary range. The postulated relatively rapid decrease in e¯ between 650 and 430 Ma may partly reflect special conditions at the CMB which caused significant increase in dissipative core-mantle torques at that time. This inflection in the curve of e¯ versus time centred at = e¯ 45°also may be partly explained by the function e⋅p ∞ (Ω2/ω)(sin2e), where ω is the Earth's rate of rotation, and other dynamical effects on e⋅p. The Proterozoic-Phanerozoic transition may record profound change in global state caused by reduction in e¯ through the critical values of 54° and 45°. The postulated flip-over of climatic zonation at ∼ 610 Ma (e¯= 54°) coincides with the widespread appearance of the Ediacaran metazoans at ∼ 620−590Ma, and the interval of most rapid reduction of obliquity and seasonality at ∼ 550Ma (e¯= 45°) with the “Cambrian explosion” of biota at 550 ± 20Ma. These two most spectacular radiations in the history of life thus may mark the passage from an inhospitable global state of reverse climatic zonation and extreme seasonality (the Earth's Precambrian “Uranian” obliquity state) to a relatively benign state of normal climatic zonation and moderate seasonality. Further geological, palaeomagnetic and geochronological studies of Precambrian glaciogenic and aeolian deposits can test the predictions of a large obliquity (e > 54°) and reverse climatic zonation and zonal surface winds during the pre-Ediacaran Precambrian.

The Late Ordovician-Early Silurian Mallowa Salt of the Carribuddy Group, Canning Basin, north-west Australia, is the largest halite deposit known in Australia, attaining thicknesses of 800 m or more within an area of approximately 200 000 km2. Study of 675 m of drill core from BHP-Utah Minerals’ Brooke No. 1 well in the Willara Sub-basin indicates that the Mallowa Salt accumulated within a saltern (dominantly subaqueous evaporite water body) that was subject to recurrent freshening, desiccation and exposure. Textures and bromine signatures imply a shallow water to ephemeral hypersaline environment typified by increasing salinity and shallowing into evaporitic mudflat conditions toward the top of halite-mudstone cycles (Type 2) and the less common dolomite/anhydrite-halite-mudstone cycles (Type 1). The borate mineral priceite occurs in the capping mudstones of some cycles, reinforcing the idea of an increasing continental influence toward the top of mudstone-capped halite cycles. The rock salt in both Type 1 and Type 2 cycles typically comprises a mosaic of large, randomly orientated, interlocking halite crystals that formed during early diagenesis. It only partially preserves a primary sedimentary fabric of vertically elongate crystals, some with remnant aligned chevrons. Intraformational hiati, halite karst tubes and solution pits attest to episodic dissolution. Stacked Type 2 cycles dominate; occasional major recharges of less saline, perhaps marine, waters in the same area produced Type I cycles. The envisaged saltern conditions were comparable in many ways to those prevailing during the deposition of halite cycles of the Permian Salado Formation in New Mexico and the Permian San Andres Formation of the Palo Duro Basin area in Texas. However, in the Canning Basin the cycles are characterized by a much lower proportion of anhydrite, implying perhaps a greater degree of continental restriction to the basin. The moderately high level of bromine in the Mallowa Salt (156·5 ± 43·5 ppm Br for primary halite, 146·1 ± 54·7 ppm Br for secondary halite) accords with evolved continental brines, although highly evaporative minerals such as polyhalite and magnesite are absent. The bromine levels suggest little or no dissolution/reprecipitation of primary halite and yet, paradoxically, there is little preservation of the primary depositional fabric. The preservation of early halite cements and replacement textures supports the idea of an early shutdown of brine flow paths, probably at burial depths of no more than a few metres, and the resultant preservation of primary bromine values in the secondary halite.

Previous palaeomagnetic study of a ∼ 10 m thick rhythmite member of the Elatina Formation, part of the Late Proterozoic (∼ 650 Ma) Marinoan glacial succession in South Australia, argued strongly for a low palaeolatitude (∼ 5°) of deposition. However, a fold test was thwarted by the approximate alignment of the remanence with the axis of tectonic folding. Here we report results of a fold test on soft-sediment slump folds with a wavelength of 14–22 cm in the Elatina rhythmites, the axes of which are approximately perpendicular to the direction of remanence. Fifty-one standard palaeomagnetic specimens sampled across the slump structure gave α95 = 3.7° prior to unfolding, α95 = 1.8° with 67% unfolding, and α95 = 2.4° with 100% unfolding. The results indicate that the remanence was acquired very soon after deposition; apparently it was acquired prior to soft-sediment slumping and then slightly sheared by the disturbance. The Elatina pole must be considered a virtual geomagnetic pole because the tidal rhythmite member studied represents only 60–70 years of deposition. However, the mean pole position is similar to other Late Proterozoic poles for South Australia, which implies that the very low inclination (< 10°) for the Elatina rhythmites does not record a geomagnetic excursion or reversal but does indeed indicate deposition in low palaeolatitudes. The similarity of many of the Late Proterozoic pole positions is evidence also that inclination error is not significant. The low palaeolatitude of Late Proterozoic glaciation is one of the major enigmas in contemporary Earth science, raising questions concerning the nature of the geomagnetic field, climatic zonation, and the Earth's rotational parameters in Late Proterozoic time.

The Acraman structure, located in the Gawler Range Volcanics, Gawler Craton, South Australia, is the largest probable meteorite impact structure known in Australia; it is notable also as the likely source of volcaniclastic ejecta within the Late Proterozoic Bunyeroo Formation located ∼ 300 km east of the impact site and within the correlative Rodda Beds in the Officer Basin ∼ 450 km to the northwest of the impact site. Conventional K/Ar analyses and 40Ar/39Ar total fusion and step heat experiments were performed on two samples of meltrock from the centre of the Acraman structure in an attempt to directly constrain the age of the impact event. The two samples of devitrified meltrock consist primarily of albite microlites in a hematitic devitrified matrix of cloudy K‐feldspar and quartz. Electron microprobe analyses of the samples reveal that the albite + potassium feldspar have nearly pure end‐member compositions (Ab99 and Or97) indicating they are likely low‐temperature authigenic phases. K/Ar, 40Ar/39Ar ...

Palaeomagnetic data for meltrock from the Acraman impact structure, South Australia, indicate a stable magnetization and a virtual geomagnetic pole that is in close agreement with the palaeomagnetic pole for the Late Proterozoic (∼ 600 Ma) Bunyeroo Formation in the Adelaide Geosyncline. The palaeomagnetic data are therefore consistent with the correlation of the Acraman impact event and deposition of the widespread impact ejecta horizon in the Bunyeroo Formation.

Fourteen obligate tetrahedral tetrads, assigned to Tetrahedraletes medinensis Strother & Traverse 1979, have been identified in a palynological assemblage derived from a core of the Mallowa Salt, the principal rock salt formation of the Carribuddy Group, Canning Basin, Western Australia. This is the first record of the genus and species in Australia, and is the earliest known occurrence of land plant spores in Australia. The species is a typical element of Gray's (1985) Microfossil Assemblage Zone 1 of mid‐Ordovician (Caradocian) to mid‐late Early Silurian (Llandovery) age, and is known currently from North America, Europe, Africa and South America. The mean dimensions of the specimens from the Mallowa Salt are within the range of specimens from assemblages of Late Ordovician to earliest Silurian age. These findings provide the firmest age yet determined for the Mallowa Salt of the Carribuddy Group.

The Mallowa Salt of the early Palaeozoic Carribuddy Group, Canning Basin, Western Australia, is a halite-mudstone-anhydrite-dolomite evaporite sequence of Late Ordovician to Early Silurian age deposited in barred marginal-marine to ephemeral saltpan and saline mudflat environments. BHP-Utah Minerals' potash exploration well Gingerah Hill No. 1 obtained drill core of a 477 m stratigraphic interval of the Mallowa Salt, which permitted the study of geochemical variations in a thick halite sequence contemporaneous with Late Ordovician-Early Silurian glaciation on other continents. A strip of uniform width was continuously ground from the core and the powdered rock bagged at 1 m intervals for geochemical assay. The resulting geochemical stratigraphic series display conspicuous cyclicity: several orders of cycles ranging from ∼ 3 m to100 + m stratigraphic thickness are discernible in the plots of minor constituents Br, MgO and K2O in extracted soluble salts and also in the plots of Na2O and total salts content. Fast Fourier transform (FFT) of the Br, MgO and K2O series gives principal spectral peaks in the 0.00–0.10 cycles/m frequency band at ∼ 250, 113, 35.4, 22.1 and 19.7 m, as well as peaks at ∼ 65 m and between 2.8 and 13.5 m. FFT of the Na2O and total salts series shows dominant spectral peaks at 220–259 and 109–114 m. If the strongest spectral peak at 113 m is taken to represent the relatively stable eccentricity period of 100 ka and a constant net rate of accretion assumed for long sections, the other main periods in the Mallowa Salt as exemplified by the Br spectrum would be31.3 ± 3.0,19.6 ± 1.1 and17.4 ± 1.1 ka. These figures are consistent with predicted Late Ordovician-Early Silurian (440 Ma) periods for obliquity (30.5 ka) and precession (19.3 and 16.4 ka) based on evolutionary change in the Earth-Moon system. Additional spectral peaks identified with implied periods of approximately 206–233, 57.5, 8–12 and 2.5–3.5 ka also may be of palaeoclimatic relevance. The relative amplitudes and structure of spectral peaks in the 0.00–0.10 cycles/m frequency band support the identification of climatic oscillations forced by orbital cycles. The data indicate a precession-eccentricity-dominated pattern, which accords with the know low palaeolatitude (

The recent recognition of cyclically laminated tidal rhythmites provides a new approach to tracing the dynamic history of the Earth-Moon system. Late Proterozoic (-5650 Ma) elastic rhythmites in South Australia represent an unsurpassed palaeotidal record of -560 years' duration that provides numerous palaeorotational parameters. At -5650 Ma there were 13.1+-0.1 lunar months/year, 400+-7 solar days/year, and 30.5+-0.5 solar days/lunar month. The lunar apsides and lunar nodal cycles were then 9.7+-0.1 years and 19.5+-0.5 years, respectively. The indicated mean Earth-Moon distance of 58.28+-0.30 Earth radii at -5650 Ma gives a mean rate of lunar retreat of 1.95+-0.29 cm/year since that time, about half the present rate of lunar retreat of 3.7+-0.2 cm/year obtained by lunar laser ranging. The rhythmite data imply a substantial obliquity of the ecliptic at -5650 Ma, and indicate virtually no overall change in the Earth's moment of inertia, which militates against significant Earth expansion since -5650 Ma. Early Proterozoic (-52, 500 Ma) cyclic banded iron-formation in Western Australia, that may record submarine fumarolic activity triggered by earth tides, suggests -514.5+-0.5 lunar months/year and a mean Earth-Moon distance of -554.6 Earth radii at -52, 500 Ma. The combined rhythmite data suggest a mean rate of lunar retreat of -51.27 cm/year during the Proterozoic (-52, 500-650 Ma); the indicated increasing mean rate of lunar retreat since -52, 500 Ma is consistent with increasing oceanic tidal dissipation as the Earth's rotation slows. A close approach of the Moon during earlier time is uncertain. Continued study of tidal rhythmites promises to further illuminate the evolving dynamics of the Earth-Moon system.

Feeding problems occur in children who have normal development, who have failure to thrive, and who have developmental disabilities. This article focuses on the latter two groups. The characteristics and developmental concerns include family characteristics, parent-child interactions, cognitive development, and oral-motor development. The evaluation process for children with feeding problems should include an interdisciplinary approach with a medical, nutritional, occupational therapy, and behavioral evaluation. The behavioral treatments include the Premack principle, time-out plus reinforcement, and negative reinforcement. Future research should focus on the parent-child interaction process in both mealtime and nonmealtime situations, along with demonstrating parents' and teachers' ability to implement mealtime treatment protocols.

The research was designed to validate procedures to teach apartment upkeep skills to severely handicapped clients with various categorical disabilities. Methodological features of this research included performance comparisons between general and specific task analyses, effect of an impasse correction baseline procedure, social validation of training goals, natural environment assessments and contingencies, as well as long-term follow-up. Subjects were taught to perform upkeep responses on their air conditioner-heating unit, electric range, refrigerator, and electrical appliances within the context of a multiple-probe across subjects experimental design. The results showed acquisition, long-term maintenance, and generalization of the upkeep skills to a nontraining apartment. General task analyses were recommended for assessment and specific task analyses for training. The impasse correction procedure generally did not produce acquisition.

Sedimentary rhythmites of siltstone and fine sandstone from late Precambrian (c. 650–800 Ma) glaciogenic formations in South Australia are interpreted as distal ebb-tidal deposits that record variability in the velocity and range of palaeo-ebb tides. Variations in lamina thickness encode a full spectrum of palaeotidal cycles, including semidiurnal, diurnal, fortnightly and monthly tidal cycles as well as the lunar apsides (perigee) and nodal cycles. A half-yearly oscillation is attributable largely to a beat between the fortnightly tidal cycles of luni-solar conjunction and lunar declination; the lunar nodal cycle is discernible as an amplitude modulation of this beat oscillation. The data allow determination of the Earth9s palaeorotation and the past dynamics of the Earth-Moon system with an accuracy previously unattainable for the Precambrian. The late Precambrian (c. 650 Ma) year contained 13.1 (±0.5) lunar months and c. 400 (±20) days, and the late Precambrian lunar month c. 30.5 (±1.5) days. These values suggest an average equivalent phase lag near 3 ° since late Precambrian time rather than the present value of 6 ° . The period of 19.5 (±0.5) years determined for the lunar nodal cycle c . 650 Ma ago indicates a lunar distance 96.9 (±1.7)% of the present distance. The low rate of lunar recession since late Precambrian time revealed by the rhythmite data militates against a close approach of the Moon during the Proterozoic. Precambrian sedimentary rhythmites may hold a key to the early history of the Earth9s rotation.

The unconformity beneath the Torridonian (late Precambrian) sediments of northwest Scotland represents one of the most ancient of fossil landform assemblages. Cut across crystalline Lewisian rocks, it is highly irregular in most places, the relief locally reaching 1,000 m. This rugged surface is little weathered. In the extreme north, however, the unconformity generally parallels the major stratification of the sediments above. Before its burial, this planar surface was weathered to depths of several metres then partly stripped of its altered mantle. A solitary hill of gneiss represents the only major relief in the unconformity within this northern district. A piedmont alluvial fan environment is suggested by the overlying arkosic sediments. The planar, weathered surface and the solitary hill thus appear analogous to a pediment and knoll buried beneath alluvial fan deposits. Vertical variations in the sediments are consistent with the planar surface having formed contemporaneously with sedimentation as a ...

Synopsis The late-Precambrian Torridonian sediments of the Cape Wrath district, extreme north-west Scotland, unconformably overlie a planar, weathered Lewisian surface. The weathered profile present beneath the unconformity is regarded as Torridonian in age, and hence must rank with the oldest palaeosols in the world. This planar surface was partly stripped of its mantle of altered rock prior to burial beneath Torridonian alluvial fan deposits. Where developed on biotite-gneiss, the weathered profile has the chemical characteristics of a modern pedalfer. A pedocal-type soil developed on amphibolite. The chemical and mineralogical changes are suggestive of a warm, moderately humid climate, possibly with dry periods or a dry season. A similarly weathered Lewisian terrain could, in principle, have supplied the bulk of the overlying Torridonian sediments.

Between February 5 and March 8, 1967, central Australia received some of its heaviest rains on record. Derived from three separate southward intrusions of monsoonal weather, the rains gave total gaugings of 120–350 mm, with some stations receiving overnight falls of over 150 mm. The ensuing floods were the most devastating in the western Lake Eyre basin in living memory. Accurate hydrological data are available only for the Todd and Finke rivers. During the 1967 floods the Todd attained a maximum gauge height of 2.17 m and a mean velocity of 1.95 m/sec; the Finke, a maximum gauge height of 6.95 m. Other major streams flooded to depths of 3–5 m and locally spread to widths of several kilometres. On March 15, floodwaters were observed entering Lake Eyre by way of the Macumba and the Neales. Finke waters did not reach Lake Eyre, being absorbed by the sands of the Simpson Desert. Large-scale ripples (dunes) were preserved on most sand-bed channels at the recession of the floods, indicating that subcritical flow prevailed for most streams. By estimating the Froude number (F) and the Darcy-Weisbach resistance coefficient ( f ) for large-scale ripples, mean stream velocities of about 0.8–2.8 m/sec have been calculated for such channels. In contrast, flat-bedded sand with parting lineation was deposited in the middle reach of the Finke. It is estimated that there the Finke attained a mean velocity of about 3 m/sec and a peak discharge of about 1200 m 3 /sec.

This study investigates the deposits of sand-bed ephemeral streams within an area of 250,000 km2 in the western Lake Eyre basin, central Australia, being initiated after the record floods of February–March 1967. Large-scale ripples were the most common bed forms preserved in the majority of channels, covering 30–40% of the depositional area. Other bed forms included longitudinal, transverse and linguoid bars (20%), upper-regime plane beds (

The comparison of 14 C ages determined for pedogenic carbonate and coexisting organic carbon obtained from arid zone calcareous soils and paleosols indicates that the carbonate dates are on average at least 3600 radiocarbon years too old. This is attributed to an initial low 14 C content of soil carbonate and minimal secondary contamination by environmental 14 C within the arid zone.

Measurement of the cross-stratification in Moinian (Precambrian) psammitic rocks at Faraid Head, northwest Scotland, indicates a strong northerly component in the direction of currents within the Moinian depositional basin.

A major probable impact structure occurs in middle Proterozoic dacitic volcanics in the Gawler Ranges, central South Australia. The structure has an inner depressed area about 30 kilometers in diameter that contains the Lake Acraman salina, an intermediate depression or ring about 90 kilometers in diameter, and a possible outer ring approximately 160 kilometers in diameter. Outcrops of dacite in Lake Acraman are intensely shattered and contain shatter cones and multiple sets of shock lamellac in quartz grains. The Acraman structure is the largest probable impact structure known in Australia and is the likely source of dacitic ejecta found in late Precambrian marine shales some 300 kilometers to the east.

Large-scale lunate ripple marks are preserved on the dry, sandy bed of a channel crossing a piedmont plain in South Australia, Longitudinal and transverse sections through the channel bed reveal that the ripple marks have deposited typical large-scale trough cross-stratified cosets.

THE distribution pattern of australites (Australian tektites) should assist in solving the puzzle of their origin. It is, however, difficult to pinpoint localities, for most collections have been made by laymen with scant regard for the importance of location. Efforts have, nevertheless, been made to record and interpret australite distribution throughout Australia1–4, demonstrating that australites are concentrated in certain regions and that there is a fairly definite northern boundary to their occurrence (inset, Fig. 1). The concentrations do not result simply from favourable conditions of exposure, although locally such conditions certainly influence discovery. Further, the australites from various regions differ in size2, shape1,2 and specific gravity5.

Planar-tabular cross-stratified sets in the Torridonian sandstones (Precambrian) of northwest Scotland are described whose cross-strata are inclined at wide angles to local paleocurrent directions. Sedimentary structures within the sets suggest that they formed on the point bars of shallow streams. A braided stream environment seems likely, although similar structures have not as yet been observed in the deposits of modern braided streams. The preferred direction of migration of streams could be of great paleogeographic significance.

J. Goguel's suggestion (Eos, 63(17)) that the cyclic lamination of the late Precambrian Elatina Formation (see cover of Eos, 63(A)) records tidal rhythms on a tidal flat cannot be sustained for several reasons. 1. The cyclic portion of the Elatina Formation is composed mostly of vertically graded laminae ranging from very fine sand through clay grade. Sedimentological study of the sequence and adjacent formations indicates a periglacial lacustrine environment of deposition for the cyclic rocks. The graded laminae are best attributed to deposition by density underflows or turbidity currents, which is the dominant mechanism of deposition in many glacial lakes today. The lack of scouring, cross lamination, and shallow-water indicators in the Precambrian cyclic rocks indicates deposition below wave base in relatively deep water. A tidal flat origin for the cyclic lamination therefore can be rejected.

Paleotidal cycles ranging from semidiurnal to the lunar nodal cycle apparently are recorded by late Precambrian (∼650 Ma) rhythmically laminated sedimentary rocks (rhythmites) of postulated ebb-tidal origin in South Australia. The rhythmites may provide unique information on paleotidal periods and Earth's paleorotation: the late Precambrian year contained in ∼13.1 (±0.5) lunar months and ∼400 (±20) days, and the late Precambrian lunar month ∼30.5 (±1.5) days; the periods of the lunar apsides and lunar nodal cycles were then 9.7 (±0.3) and 19.5 (±0.5) years respectively. These values suggest that since late Precambrian time the average equivalent phase lag [the angle between the Earth-Moon axis and Earth's tidal bulge, derived from the response of the solid and ocean tides; Lambeck, 1980] was near 3° rather than the present value of 6°. Precambrian sedimentary rhythmites may record much valuable information on the early history of Earth's rotation and the lunar orbit.

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Field study and radiocarbon dating of authigenic carbonate in arid-zone paleosols and calcretes have been carried out in Australia to determine the reliability of this method of soil dating. Three calcareous paleosols of late Quaternary age are developed within alluvial and eolian deposits on the Lake Torrens plain in arid South Australia. Dates for organic carbon obtained from the sediments show that soil-forming episodes took place shortly after 30,000 yrs B.P., between about 16,000 and 12,000 yrs B.P., and between 6,000 and 1,500 yrs B.P. Respective mean radiocarbon ages determined for pedogenic carbonate are (with approximate scatter) 27,450 (± 7,000) yrs B.P., 13,900 (± 2,000) yrs B.P., and 7,750 yrs (± 1,000) B.P. Although the great majority of the individual carbonate dates and the three mean dates are sound as relative ages, they are less reliable as absolute ages. A review of the literature reveals that most carbonate dates for arid-zone paleosols and calcretes which have been dated by coexisting organic carbon are from about 500 to 7,000 radiocarbon years too old. This is attributed to an initial low C 14 /C 12 ratio in soil carbonate, reflecting low C 14 content of source carbonate. Postformation contamination with C 14 commonly appears to be minimal in the arid zone, where dates for micritic carbonate from well-drained sites should approximate to or be up to several thousand years older than true ages of soil formation. Age correction based on δC 13 values for soil carbonate is invalid.

Sediments of three major basins occur in the Simpson Desert region of central Australia:Cambro -Ordovician dolomites and sandstones, and Siluro- Devonian conglomerates, sandstones and shales, related to the Amadeus Basin:Permian conglomerates, sandstones, shales and coals of the Simpson Desert Sub-basin, the extensive eastern lobe of the Pedirka Basin:Mesozoic sandstones and shales of the Eromanga Basin.Principal petroleum exploration interest is presently directed toward the Permian sediments, which have many features in common with the petroleum producing Permian section of the neighbouring Cooper Basin.Lower Permian sediments known from drilling in the Simpson Desert Sub-basin comprise glaciofluvial conglomerates and sandstones overlain by fluvial and lacustrine sandstones, silt-stones, shales and coals. The maximum thickness encountered in wells is 1,479 ft (448 m) in Mokari 1.Recent seismic exploration 50 to 100 mi (80-160 km) west of Poeppel Corner in the deeper part of the Simpson Desert Sub-basin indicates that an additional sediment package up to 1,500 ft (350 m) thick occurs at depths of 6,500 to 7,500 ft (2,000-2,300 m) between Lower Permian and Lower Jurassic sections. This sediment package, nowhere penetrated by drilling, may be Middle to Upper Permian and/or Triassic in age. It is of great significance to petroleum exploration in the sub-basin and substantially upgrades the hydrocarbon prospects of the region.Permian sediments in the Simpson Desert Sub-basin thin by onlap, wedge out and stripping over the crests of anticlinal growth structures. Crestal sediments probably comprise mainly porous sandstones, grading off-structure into thicker sequences containing carbonaceous shales and coals. Such carbonaceous potential source rocks are probably best developed in the deepest part of the sub-basin, where Triassic cap rock may also be present. Two particularly promising drilling targets—the Colson Anticline and the East Colson Anticline—have been revealed by recent geophysical surveys in this portion of the sub-basin. Wells drilled on these structures may intersect Permo-Triassic sediments up to 2,200 + ft (670 in) thick which are comparable in age and type with producing sections in the Cooper Basin.