Revisit of Caliche Profile Classification: Case Studies from Texas
Idealized caliche profiles are composed of a sequence of facies that reflect the pathway through which the caliche accumulated over geological time. Currently, two general types of caliche profiles, which are characterized by either the growth of nodules or gravel coatings in their initial stages, have been widely recognized (Gile et al., 1966, Esteban and Klappa, 1983; Machette, 1985). However, these two classifications do not represent all caliche development on variable substrates around the world.
A four-fold classification scheme is proposed based on the investigation of 51 caliche profiles that developed on various host rocks (including limestone, alluvium, eolian, igneous, and metamorphic) and across 900 km from humid east Texas to arid west Texas. Profiles A, B, C, and D differ in their lower parts, and are characterized by nodular, friable massive, gravel coating, and fracture-fill facies, respectively. These are products of calichification in their youthful stages, which are, in general, successively overlain by caliche hardpans, laminar crusts, and pisoids when the profiles evolve to more mature stages. The type of caliche profile is not strictly bedrock lithology specific. Instead, the complex relationship between bedrock and caliche profile is mainly controlled by two factors: (1) intrinsic, mainly texture (i.e., grain size, induration, and clay content), and (2) extrinsic (i.e., weathering intensity).
The differentiation of four types of caliche profiles is more comprehensive than previous schemes and includes the development of caliches on various substrates and under different climatic conditions.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009