Cements phreatic

Fig. 15. Plot of 5 C versus 8 0, with individual points identified by cementation types. Vadose types include nodule, platy and rod concretions, as well as type 2 tabular units. Phreatic types include ovoid to elongate concretions as well as type 1 tabular units. In general vadose cements have heavier carbon values and lighter oxygen values than phreatic cements. Phreatic and type 3 (phreatic) units that plot with oxygen values greater than -10 are from the upper part of the Unnamed Member.

Chung GS, Swart PK (1990) The concentrahon of ttranium in freshwater vadose and phreatic cements in a Holocene ooid clay a method of identifying ancient water tables. J Sediment Petrol 60 735-746 Cliff RA, Spotl C (2001) U-Pb dahng of speleothems from the Spannagel Cave, Austria. XI EUG... 

A few experiments have been successfully performed at low temperatures to simulate carbonate diagenetic processes for example, cements have been precipitated on skeletal carbonate sands in experimental reaction chambers designed to mimic vadose and phreatic meteoric cementation (Thorstenson et al., 1972 Badiozamani et al., 1977). These cements are remarkably similar in composition and morphology to those found in rocks cemented in the meteoric... 

Figure 7.16. Different types of cements precipitated in the vadose (left) and phreatic (right) parts of the meteoric diagenetic environment. Epitaxial cements may be precipitated in either environment. (After James and Choquette, 1984.)...

Figure 7.42. Comparison between (A) an idealized plot of variation in 8180 and 813C for carbonates subjected to vadose and phreatic meteoric diagenesis (after Lohmann, 1988) with (B) the meteoric alteration trend observed for the Key Largo Limestone, Florida, U.S.A. (after Martin et al., 1986). The critical trend in isotopic composition is termed the meteoric calcite line. This trend may be modified at the water recharge surface where evaporation is an important process, caliche is formed and the diagenetic phases are depleted in 13C derived from soil-gas CO2. Another modification can occur distally to the recharge area where precipitating carbonate cements may have isotopic ratios nearly equivalent to dissolving phases.

Badiozamani K Mackenzie F.T. and Thorstenson D.C. (1977) Experimental carbonate cementation Salinity, temperature, and vadose-phreatic effects. J. Sediment. Petrol. 47, 529-542. 

Beckner J. R. and Mozley P. S. (1998) Origin and spatial distribution of early vadose and phreatic calcite cements in the Zia Formation, Albuquerque Basin, New Mexico, USA. In Carbonate Cementation in Sandstones. Distribution Patterns and Geochemical Evolution (ed. S. Morad). International Association of Sedimentologists, Oxford, vol. 26, pp. 27-52. 

Aeolianites that become submerged below the groundwater table may become cemented in the phreatic environment. In this zone, pore spaces between sand grains are completely filled with water and any cements derived from the interstitial waters are often isopachous in nature (Muller, 1971). Large solution volumes and longer residence times in the phreatic zone can result in coarser spar compared with the vadose zone. Increases in temperature, degree of supersaturation and NaCl content appear to result in larger cement crystal sizes (Badiozamani et al., 1977). 

Origin and spatial distribution of early vadose and phreatic calcite cements in the Zia Formation, Albuquerque Basin, New Mexico, USA... 

ES Aeolian sandsheet deposits Low angle cross-bedded sand (Sle) horizontally laminated sand (She) ripple cross-laminated sand (Sre) Tabular 1-2 m thick >1 km lateral extent Fine to medium moderately to poorly sorted sand/sandstone Coarser layers often form well cemented type 1 and type 3 (phreatic)... 

Thinly bedded type-3(phreatic) tabular unit. Coarser laminae are better cemented giving /unit a platy appearance. 

Fig. 7. Spatial distribution of cementation types in the Zia Formation. Note the association of laterally extensive phreatic units with sand lithologies. Laterally extensive vadose units are not associated with any particular depositional environment.

We have inferred the environments of cement formation in the Zia Formation by comparing microscopic and macroscopic characteristics with those of cements of known origin described in the literature. In this section we discuss known characteristics of vadose and phreatic cements, and use this as the basis for identification of cementation environments in the Zia Formation. 

Phreatic (ovoid and elongate concretions, and type-1 tabular units) Mixed type-3 (phreatic) tabular units A Fault cements... 

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