Genesis of podzols on coastal dunes in southern Queensland. V. Chemistry and mineralogy of the non-opaque heavy mineral fraction

Abstract

Eight podzols on coastal dunes from the Cooloola chronosequence, and an associated pedon from North Stradbroke Island (Amity), were studied to establish (i) the degree of homogeneity of the parent material between and within profiles, (ii) the extent of heavy mineral weathering, and (iii) whether the parent sediments of each pedon had a common proximate source. The pedons are Quartzipsamments and Troporthods with ages ranging from Holocene to Pleistocene. On the basis of ratios zircon : rutile, zirconium : titanium, and non-magnetic : very magnetic heavy minerals in the fine sand fraction (53–125 µm), we concluded that the parent materials of the Cooloola pedons were mineralogically similar. By using zirconium in the non magnetic heavy mineral fraction as an index for zircon, it is evident that there has been considerable pedogenetic weathering of the heavy mineral fraction. There is a statistically insignificant difference in hafnium concentrations of zircons which implies that parent sediments of the soils at Cooloola and North Stradbroke Island were derived from a common immediate source.

Nutrient retention by tropical ecosystems: soil adsorption and plant absorption as synergistic processes

“…The dune system comprises a quartzitic sand mass in which a system of podzols have formed that vary from incipient to giant podzols > 20 m deep and c. 730 000 y old (Tejan-Kella et al 1990, Thompson 1981. Parent material of all soils in the system is similar (Chittleborough et al 1998) and consists of quartz sand grains of marine origin with thin sesquioxide coatings. During soil formation these coatings are mobilized and translocated to B horizons at progressively greater depths, leaving behind an A2 horizon of bleached quartz grains that gradually deepens to 12-20 m (Thompson 1983).…”

Soil organic matter turnover over decadal to millennial timescales

“…Rocky headlands in South-East Queensland may have acted as natural groynes where the sands have deposited at different stages during marine transgressions (Roy and Thorn, 1981 After deposition, aeolian processes pushed the sands further inland, forming parabolic dunes (Panel 1) which are still recognisable today (Coaldrake, 1960;Thompson, 1983). While it is implied in earlier publications, it was confirmed later on, based on a constant Zr/Hf ratio of the zircons, all the sands derive from the same parent material (Chittleborough et al, 1998;Fitzpatrick and Chittleborough, 2002). The overlapping systems that are a result of the dune-building process have formed a sequence of varying aged dunes, collectively termed a "chronosequence".…”

“…deposited from yet uncertain offshore sources during marine transgressions (see review by Miot da Silva and Shulmeister, 2016) but is of consistent origin amongst all dune systems (based on Xr:F ratio; Chittleborough et al, 1998).…”

“…It was initially believed (Brewer and Thompson, 1980) that SOM interacted with Fe ions to give rise to the podzol B horizons at Cooloola, however sequential extractions by Skjemstad et al (1992b) released from the sand grain, they interact to form disordered aluminosilicates that leach from the surface and precipitate as short-range ordered (SRO) proto-imogolite further down the profile to initiate the B horizon (Skjemstad et al, 1992b). This accumulation then adsorbs translocating DOM and other SRO minerals (such as Fe, Ti and Mn in their poorly-crystalline phases) being leached down the profile which further progresses B horizon development (Chittleborough et al, 1998;Fitzpatrick and Chittleborough, 2002).…”