The C/C ratio in pedogenic carbonate (i.e., CaCO3 formed in soil) is a significant tool for investigating C4 biomes of the past. However, the paleoecological meaning of dC values in pedogenic carbonate can change with the scale at which one considers the data. We describe studies of modern soils, fossil soils, and vegetation change in the Chihuahuan Desert of North America and elsewhere that re...

A 4.5 Ma record of fluvial and lacustrine deposits is well exposed at Gona, in the Afar Depression of Ethiopia. We use isotopic values of pedogenic carbonate and fossil teeth to reconstruct Plio^Pleistocene environmental change at Gona. An increase in N13C values of pedogenic carbonates since 4.5 Ma points to a shift from woodlands to grassy woodlands in the early Pliocene, 310.4 to 33.9x (VPDB...

Late Quaternary soils in southern New Mexico support previous work that suggested pedogenic gypsum accumulates in successive stages as a function of time, similar to pedogenic carbonate. However, gypsum also occurs as small (0·5}1 mm), powdery spheres that we term snowball morphology. The snowball morphology represents one of the initial stages of pedogenic gypsum development. Scanning electron...

Soils overlying two porphyry Cu deposits (Spence, Gaby Sur) and the Pampa del Tamarugal, Atacama Desert, Northern Chile were collected in order to investigate the extent to which saline groundwaters influence ‘‘soil’’ chemistry in regions with thick Miocene and younger sediment cover. Soil carbonate (calcite) was analyzed for C and O isotopes and pedogenic gypsum for S isotopes. Soil calcite is...

Oxygen isotope ratios of pedogenic carbonates were analyzed along a climatic gradient in the Palouse region of eastern Washington State to evaluate changes in their isotopic composition with changing climate. A modern analog approach was used to assess the relationship between the istotope ratios in the pedogenic carbonates with those in soil water (measured in June when we anticipated carbonat...

Carbonate oxygen isotope paleoaltimetry is based on analysis of the dO value of carbonate precipitated from surface water. Deciphering the diagenetic history is important for establishing whether particular carbonates are accurate recorders of paleosurface waters, which reflect paleoelevation. This study provides examples from southern, east–central, and northeastern Tibet of approaches aimed a...

the micromorphology of pedogenic carbonate features in calcareous soils of arid and semiarid regions of kohgilouye province, southwestern iran, has been studied to determine their genesis and distribution in different climatic regions. eight representative pedons (from a total number of 24 pedons) were studied in aridic-ustic (minimum rainfall), ustic and xeric (maximum rainfall) soil moisture ...

Coeval !!"C shifts recorded in buried soils at both piedmont slope and basin floor sites in the northern Chihuahuan Desert indicate a major shift from C # grasses to C " desert-scrub between 7 and 9 ka. The age assignments are based on stratigraphic correlations to charcoal dates and carbon-14 dates of carbonate. This shift is synchronous with a period of cooling in the North Atlantic that may ...

Analysis of 171 samples taken from the Neogene cohesive soils of the Southeastern edge of the Granada basin shows inverse correlation between carbonate content and dispersion index and swelling behaviour and direct correlations between carbonate content and shear strength. This paper shows that carbonate content and clay fraction activity have a great influence on the compaction characteristics...