Abstract Caliche is used as a genus of soil-mineral accumulations, including calcareous, siliceous, ferruginous, aluminous and nitrogenous varieties in young, mature, and aged stages. Calcareous caliche (some travertine, sinter or tufa), quartzite, chalcedony, opal, iron oxides and hydrated oxides, kaolinite, bauxite, and laterite occur as caliches. Prolonged leaching of the surface soil on young plains and peneplains, with deposition of leached minerals in a constantly descending zone 3–10 feet underground, forms horizontal layers of caliche minerals to produce a formation, the duricrust, of surficial, continental origin, transgressing older beds. Climatic zonation of caliches is noted. Soil carbonates accumulated in semi-arid, less soluble soil minerals in humid, zones. After strong leaching removes carbonates, less soluble caliches accumulate even in the arid zones. Desert caliches are tough, including the glazes. The Reynosa formation consists of 85 feet of upper caliches, alluvial sands, silts, and gravels formed on a post-Oakville or post-Lagarto plain, with several soil (caliche) beds. The Lower Reynosa is slightly thicker (not 600 or 1,500 feet, as some report), including gray sandstones, gray clays and conglomerates with gravel and tufa pisolites. Compact pisolitic tufa of the lower beds with land snails is of spring origin (associated with faults?). The Reynosa, including outliers up the dip, transgresses Lagarto to Cretaceous beds. The Pliocene-Pleistocene contact may separate the upper and lower divisions. The main body of the Reynosa, capped by caliche, holds up the Reynosa Plateau or cuesta, which has a mature karst topography of knolls and basins floored in the beds overlapped by the caliche. Few rivers cross the plateau. Porous sands and gravels of the Reynosa furnish water for wells and feed many streams which head in the plateau or at its east foot. The caliche obscures and confuses stratigraphy and interferes with geophysical prospecting. Karst basins ( palanganas ) are not diastrophic in origin but may be modified by "structure."

Abstract Approximately 2,000 samples were procured from 13 wells in the Gulf Coast area. As the content of organic matter in most of the samples obtained from these wells is very small, no attempt has been made to investigate the Gulf Coast area in detail. The location of the wells studied is indicated on Figure 61. A summary of the general nature of the stratigraphy in this area is given in Table 127 and in Figure 62. The sediments in the Gulf Coast region thicken southeastward and, in general, grade from continental to marine toward the Gulf; but the shore line apparently oscillated during the deposition of many of the formations, for marine and continental beds are intercalated in several places. The southwest part of the Gulf Coast area is occupied by a deep basin of Eocene deposits. The sediments exposed at the surface of the ground become progressively younger from southern Texas toward Louisiana. Near the Mississippi delta, the late Tertiary and Pleistocene formations are very thick. The Gulf Coast Tertiary section is characterized by very little limestone. The correlation of the stratigraphic units in the Gulf Coast region is attended by some uncertainty, as the exact stratigraphic equivalents of all the formations throughout the entire region can not yet be determined. This uncertainty is particularly true of the Pliocene and later formations. The Pliocene and Pleistocene units are classified under three heads: undifferentiated Pliocene, indicated by the symbol, Tp; Reynosa formation

Abstract The paper gives a general discussion of the surface formations and surface geology of the post-Fleming belt lying between the coast and the outcrop of the Fleming in southeast Texas and south Louisiana. Data and discussion are presented under four main heads, Physiography, Stratigraphy, Origin and History, and Structure. Under Physiography it is shown that the present physiography indicates the general features of the geology of the area, that is, the subdivision of the post-Fleming group into four formations, Recent, Beaumont, Lissie, and Willis, and the general structure and interrelations of these formations. Under Stratigraphy the present subdivision is correlated with earlier classifications. The formations are described. The Willis, which is a new formation roughly equivalent to the old Lafayette and Reynosa of this area, is named, subdivided into three members, and described in detail. Its relation to the Goliad formation of south Texas is discussed. Under Origin and History the deposition of these formations is credited to the ancestors of the present major streams of the coast. The peculiar stratigraphic and structural interrelations of the post-Fleming formations are attributed to cycles of deposition separated by tilting movements which affected this part of the coastal plain at intervals. Under Structure the regional structure of the formations, local irregularities, methods of mapping, and the relation of surface to subsurface structure are discussed.

Abstract The Driscoll pool is in central Duval County in southwest Texas. The surface is mantled by caliche and gravels of Recent age which makes surface geology unreliable. Sands and clays of the Reynosa or Lower Lissie formation of Pliocene age make up the surface exposures. Tests drilled in the area have penetrated Miocene, Oligocene, and as deep into the Eocene as the Cook Mountain formation. Production in the Driscoll pool is coming from the Oakville, Frio, and Fayette sands. Oil from the Fayette is 23°Bé. gravity of Mirando quality. The present three wells will produce approximately 500,000 barrels of oil, or a per-acre yield of 16,500 barrels. The pool should ultimately cover 640 acres. The structure is a sand lens controlled by folding. The Government Wells, Mirando, Pettus, and Yegua sands have not been tested but should be found in the area above 4,500 feet.