Phanerozoic sedimentary and volcanic rocks exposed in the Joyita Hills area (Socorro County, New Mexico) record structures that developed in response to three deformational episodes: ancestral Rocky Mountain, Laramide, and Rio Grande rift. Additional exposures of Proterozoic gneiss in the core of the Joyita Hills reveal three preferred orientations of high-angle to vertical, gneissic to mylonitic foliations. These strike north, northwest, and east-northeast. Proterozoic amphibolite dikes parallel the east-northeast foliations. Comparison of Phanerozoic fault and dike orientations with attitudes of Proterozoic structures indicates that reactivation of basement flaws was a factor common to each Phanerozoic orogenic event. Reactivation of Proterozoic foliations during ancestral Rocky Mountain tectonism resulted in basins and uplifts of north and northwest trend. Normal, left-oblique slip on north-striking faults and normal slip on northwest-striking faults, when combined with the orientation and spatial distribution of basins and uplifts, indicates that late Paleozoic deformation in central New Mexico was the result of north-trending, divergent, sinistral wrench faulting. Laramide tectonism reactivated Proterozoic structures in a strike-slip sense. North-striking (synthetic) and east-northeast-striking (antithetic) faults define a north-trending, dextral wrench fault system. Other dextral wrench faults strike northeast, and parallel the Montosa and Del Curto fault zones. Thrust faulting and associated folds were a lesser component of Laramide deformation, and were apparently related to Laramide wrench fault systems. Extensional reactivation of Proterozoic structures influenced the development of basins and uplifts of the Rio Grande rift. Northwest-striking and east-northeast-striking normal fault and dike systems paralleled Proterozoic foliations and amphibolite dikes. North-striking foliations and ancestral Rocky Mountain faults observed along the East Joyita fault influenced the development of this major, down-to-the-east normal fault (approximately 3 km stratigraphic throw). Moreover, north-striking foliations and ancestral Rocky Mountain structures (the north-trending Lucero basin and adjacent uplift) influenced the location and orientation of the Albuquerque Basin segment of the Rio Grande rift.

Abstract The Okefenokee swamp-marsh complex of southern Georgia is losing upward of 10 11 g per year of humic matter as a result of surface drainage.. The loss of these highly stable polymers amounts to ~50 g per m 2 per year. Because net accumulation of peat is <100 g per m 2 per year, this loss could have a significant effect on the eventual petrography of the coal which could result from Okefenokee eats. The waters leaving the swamp, notably those of the Suwannee River, carry a load of 70-100 mg/1 dissolved humic substances. These are characterized by high total acidity (>10 meq/g) and a high carboxyl content (<6 meq/g). Number average molecular weights range from ~S00 to ~5000. Elemental composition and spectral properties resemble those of soil humic substances. The organic matter contributes more than 0.4 meq/1 of acidic functional groups to the low ionic strength swamp effluents, thus controlling pH and providing anions for electrical charge balance. The presence of salicylic acid sites in the humic polymers allows the formation of strong metal chelates, in addition to other complexing reactions, which explains the linear correlation between organic carbon and iron. During periods of high discharge from the headwaters of the Suwannee, the effect of the dissolved humic matter extends to the mouth of the river, as evidenced by concentrations of 40 mg/1 organic carbon and a slow gradual increase of pH downstream to ~6.7. During periods of low discharge the karst waters from the downstream limestone terrains dominate. The organic carbon concentrations are as low as 10 mg/1, and pH values increase sharply from 4.2 to 7.2 immediately after entering the karst region.

Mineral and chemical studies of muds samples (sidewall cores) from 4233 ft to 16,450 ft deep in the Gulf of Mexico (courtesy Chevron Oil Company) and from the surface to 24,003 ft in the Anadarko Basin, Oklahoma (courtesy Shell Oil Company) were studied in order to obtain information on the diagenesis of muds during deep burial. With depth the montmorillonite in these montmorillonite-rich shales is altered to mixed-layer illite-chlorite-montmorillonite; the regularity of the mixed-layer phase tends to increase with depth. Much of the interlayer hydroxy material is A1 and Fe, acquired before deposition. K is acquired from the river and seawater, and after deposition, from K-feldspar. Increased lattice charge in the montmorillonitic layers (largely beidellite) is due to the reduction of iron in the octahedral layer and the incorporation of additional Al in the tetrahedral layer. It is suggested that the latter phenomenon is caused by the migration of interlayer Al into the hexagonal holes in the oxygen sheet. Most of the loss of expandable layers occurs by 12,000 ft. As depth and temperature increase, kaolinite is destroyed, and the Al is deposited between the expanded layers as hydroxy-Al to produce layers of dioctahedral chlorite. Both discrete dioctahedral chlorite and mixed-layer illite-dioctahedral chlorite-montmorillonite (ultimately mixed-layer illite-chlorite) are formed. During regional metamorphism the sequence is kaolinite and mixed-layer illite-montmorillonite→mixed-layer illite-dioctahedral chlorite K , Mg , Fe → muscovite + chlorite. The Al 2 O 3 content of the bulk samples ranges from 9.94 to 17.47 percent. This is equivalent to approximately 55 to 75 percent clay minerals. The Al 2 O 3 /K 2 O, Al 2 O 3 /MgO, and Al 2 O 3 /Fe 2 O 3 values of the Chevron and Mississippian (except for Al 2 O 3 /MgO) samples indicate a deficiency of K, Mg, and Fe with respect to the Paleozoic and Precambrian shales. There is an indication that these cations increase with depth and may have migrated upward from the interval where granitization is taking place. These montmorillonite-rich clays cannot be converted to the typical illite-chlorite clay suite of the older shales without the addition of K, Mg, and Fe from external sources. Dioctahedral chlorite, both as discrete chlorite and as mixed-layer illite-chlorite, is present in most Paleozoic and Precambrian shales and will be even more abundant in deeply buried Tertiary shales unless cations are added from outside the system. The data indicate that, in areas where the conversion of montmorillonite-rich clays to illite-chlorite clays occurs, the geothermal gradient is relatively high, and K, Mg, and Fe are added from below. The possibility exists that geothermal gradients were higher in the Paleozoic and Precambrian, particulary preceding the middle Carboniferous break-up of the continents. The total exchange cations (Na + K + Mg + Ca) average 30 meq/100 g down to approximately 8000 ft; deeper samples average 20 meq/100 g. The C.E.C./Al 2 O 3 values decrease to 10,000 ft, then remain constant, confirming the X-ray interpretation. The more mobile Na replaces Mg to become the dominant exchangeable cation in the shallow samples. As the expandable layers are converted to nonexpanded layers, the weakly bonded Na is released to the pores, and Ca is selectively retained. Most of the exchangeable Mg is used to form dolomite or is flushed into the sands where it combines with montmorillonite to make chlorite. The pore water content decrease to 10,300 ft abruptly increases, as high pressures are encountered, and then systematically decreases. The cation concentration in these waters is two to three times that of seawater. The cation concentration increases to 10,000 ft, abruptly decreases by 20 percent, then remains relatively constant. Na and K are more concentrated than seawater; Ca and Mg are less concentrated. K and Mg increase with depth; this is presumably a function of the increase in temperature. In the shallow samples the Na concentration increases as the pore water decreases. In deeper samples the ratio remains relatively constant. The anion concentration is HCO 3 > SO 4 > Cl. Cl systematically decreases with depth and is one-fourth the concentration of seawater by 10,000 ft. Presumably, this is due to selective flushing. Over the same depth interval, SO 4 increases by a factor of 6 to 7, comparable to the decrease in pore water, suggesting concentration by selective filtering. HCO 3 increases in concentration to 10,000 ft and then remains constant. The high HCO 3 values are due to the decomposition of organic matter and calcite. Functional organic groups are released from the clay minerals as the temperature and Na concentration increase. During burial a physical permeability barrier is formed by the rapid dewatering of the top of the thick water-rich mud section. Upward migrating Ca precipitates as calcite increasing the effectiveness of the buried mud. Na diffuses through the barrier more easily than water; Cl diffuses through more easily than SO 4 and HCO 3 .

Illite/montmorillonite (in bulk and in mixed-layer clays) increases during diagenesis, indicating that montmorillonite is altered to illite. Altering average sedimentary montmorillonite layers to average diagenetic illite layers principally involves increasing tetrahedral Al from almost nil to ~ 20 percent. Regarding possible mechanisms: (1) Al probably cannot displace Si and occupy the same tetrahedron; (2) high-energy barriers undoubtedly exist at submetamorphic temperatures to a mechanism requiring disintegration; (3) during dehydration of montmorillonite, some exchangeable cations (with radius ≤ Na + ) apparently enter through the “ditrigonal” holes in basal oxygen planes into expanded tetrahedral sites (one hydroxyl ion, three basal oxygen ions); and (4) the expanded tetrahedral sites contract to normal 4 CN packing as tetrahedral rotation increases to the theoretical maximum (30°). The proposed mechanism involves: (a) migration of interlayer Al through ditrigonal holes; (b) increased tetrahedral rotation (attraction of basal oxygens toward the Al ions in the expanded tetrahedra); (c) creation of permanent Al tetrahedra at 30° rotation; (d) expulsion of an equal number of Si to the interlayer volume; (e) additional Si migration along easy paths to new (illite) tetrahedra; (f) hydrogen ion migration to nearest neighbors within the oxygen-hydroxyl planes; and (g) continued rotation to the illite configuration. Processes (c) through (f) occur simultaneously. This mechanism is sterically possible at each structural level. Inherited illite OH-OH angles within individual layers depend on the spatial relations between the sets of tetrahedra vacated in top and bottom sheets, and on the original montmorillonite OH-OH angles. Poor stacking order in montmorillonite predetermines the 1 Md illite polytype, as has been observed in early diagenetic illites. The (Al, Si) tetrahedra are ordered in the product, illite, within each single-layer domain.