Paleoenvironmental Implications of Lacustrine Clay Minerals From the Double Lakes Formation, Southern High Plains, Texas
Published:January 01, 1994
Daniel M. Webster, Blair F. Jones, 1994. "Paleoenvironmental Implications of Lacustrine Clay Minerals From the Double Lakes Formation, Southern High Plains, Texas", Sedimentology and Geochemistry of Modern and Ancient Saline Lakes Models, Robin W. Renaut, William M. Last
Download citation file:
To investigate whether clay minerals reflect periodic variations in paleolake conditions, major-element chemical and X-ray diffraction analyses were done on ultrafine (<0.1 μm) fractions of Pleistocene-Holocene lacustrine sediments from the Double Lakes Formation, southern High Plains, Lynn County, Texas. Above a Cretaceous marine-shale substrate dominated by well-crystallized aluminous dioctahedral smectite, the clay-mineral assemblages of the younger lacustrine sediments show cyclic changes perhaps related to fluctuations in hydrologic environment and climate. The cycles apparently represent evaporatively induced salinity shifts from brackish to saline (perennial), or ephemeral-lake (playa) conditions, as inferred from the predominance of sepiolite, interstratified Mg-smectite, and palygorskite respectively. Two of at least four cycles show a complete sequence from low to high lake level and return to playa conditions. Between sediment units clearly dominated by a single clay-mineral species are intervals containing variable mixtures of chain-structure clays and smectite indicating change in the conditions of paleolake deposition. Chemically, the highest ratios of Si4+ to Al3+ are associated with sepiolite and the highest Mg2+ to Al3+ values are correlated with the abundance of interstratified smectite. Pulses of detritus associated with overland runoff and wind are indicated by high concentrations of illite and minor kaolinite, as evidenced by high K+ and Al3+ contents. Spring deposits (tufas) along a principal drainageway near the lake suggest inflow from groundwater has had a major effect on the nature of the clays.
Figures & Tables
Sedimentology and Geochemistry of Modern and Ancient Saline Lakes Models
Sedimentology and Geochemistry of Modern and Ancient Saline Lakes - This volume of papers grew out of a four-day symposium entitled ?Sedimentary and Paleolimnological Records of Saline Lakes? held at Saskatoon, Canada in August, 1991. The aim of this Special Publication is to bring together selected papers from this conference that deal specifically with the sedimentological, inorganic geochemical, and hydrological aspects of salt lakes and their stratigraphic records. This volume is divided into four sections. The first section contains papers that deal with modern saline lakes. The second section contains papers dealing with sedimentation and diagenesis of late Quaternary salt lakes. The third and fourth sections contain papers devoted to ancient (pre-Quaternary) Lacustrine sequences.