LANDFORMS, SOILS, AND LAND- hydrologic mass balance equation and ranged SCAPES OF THE PETRIFIED FOREST from ~4 to ~7 inches/yr, representing between Abstracts NATIONAL PARK, ARIZONA, by Amy L. ~14% and ~26% of the total water budget on an Ellwein, 1997, MS thesis, Department of Earth annual basis. and Planetary Sciences, University of New A ground-water flow model of the alluvial New Mexico Geology recognizes the important Mexico, Albuquerque, NM 87131, 175 pp. system was constructed using Visual MOD- research of students working in post-graduate Quaternary eolian deposits provide one very FLOW®, which implements the U.S. Geological MS and PhD programs. In this issue we begin a important type of record of landscape evolution Survey’s three-dimensional finite-difference new series of abstracts, those of recently com- in the Petrified Forest National Park. The park ground-water flow code. Both steady-state and pleted MS theses and PhD dissertations that is located on the periphery of the Tusayan dune transient simulations were run. MODFLOW’s pertain to the geology of New Mexico and field, one of the largest North American dune drain package was used to simulate infiltration neighboring states. fields. Quaternary deposits were mapped to seepage from the system, while the hydrologic delineate the distribution, morphology, and soil budget analysis results constrained the characteristics of Quaternary deposits; this evi- recharge and evapotranspiration stresses. The dence, supplemented by other types of data, steady-state model was calibrated to well data University of New Mexico was used to interpret the Quaternary geologic by varying the drain conductances. The history of the study area. The relative timing of ZONEBUDGET and MODPATH codes were eolian activity was constrained through charac- also utilized, and results showed that infiltra- QUATERNARY VOLCANISM IN THE COL- terization of stratigraphic relationships and tion seepage dominated the loss components of ORADO PLATEAU−BASIN AND RANGE degree of soil development in eolian deposits. the modeled system’s water budget, represent- TRANSITION ZONE: ZUNI−BANDERA The landscapes of the study area are typical ing ~69% of the total losses, compared to ~28% AND NEARBY VOLCANIC FIELDS, by of the southern Colorado Plateau near the Little for evapotranspiration and ~3% for downgradi- Tracey E. Cascadden, 1997, PhD dissertation, Colorado River. Where easily erodable mud- ent flow, which was characterized with an aver- Department of Earth and Planetary Sciences, stones of the Triassic Petrified Forest Formation age advective velocity of 727 ft/yr. Results also University of New Mexico, Albuquerque, are exposed, badlands develop; where the more quantified enhanced infiltration seepage within NM 87131, 187 pp. resistant sandstone units outcrop, mesas and the Guaje Mountain fault zone. An error analy- Early (ca 700 ka) voluminous tholeiites in the buttes form. Development of the modern land- sis generally corroborated the model results, Zuni−Bandera volcanic field (ZBVF) were fol- scape is largely a result of post-Pliocene fluvial and a sensitivity analysis was conducted, which lowed by smaller volume alkalic, transitional, incision. The location and stability of eolian showed that the model was most sensitive to and tholeiitic basalts intermittently erupted landforms common to this region has been sig- errors in recharge and evapotranspiration. from ca 200 ka through 3 ka. In some cases, nificantly affected by the hydrologic character- lavas of different chemical characteristics were istics of Triassic-, Pliocene-, and Quaternary-age erupted from the same vent or from contempo- geologic materials. LITHO- AND BIOSTRATIGRAPHY OF THE raneous clusters of vents. El Calderon cinder Age estimates for eolian deposits were deter- LOWER CHINLE GROUP IN EASTERN cone erupted magmas derived from two differ- mined through integration of soils data and the ARIZONA AND WEST-CENTRAL NEW ent sources. Early alkalic eruptions, derived stratigraphic relationships between eolian MEXICO, WITH A DESCRIPTION OF A from a depleted (asthenospheric) source, were deposits and landforms such as fans and pedi- NEW THEROPOD (DINOSAURIA: followed by more voluminous tholeiitic flows ments. The eolian deposits associated with THEROPODA) FROM THE BLUEWATER derived from an enriched (lithospheric) source. well-developed soils are estimated to be of mid- CREEK FORMATION, by Andrew B. The tholeiite flow erupted at ca 80 ka during a dle Pleistocene age (100–500 ka), the eolian Heckert, 1997, MS thesis, Department of Earth high-amplitude excursion (possibly an aborted deposits with relatively moderate soil develop- and Planetary Sciences, University of New reversal) of the geomagnetic field, as indicated ment are probably of middle Holocene age (2–8 Mexico, Albuquerque, NM 87131, 278 pp. by a paleomagnetic direction with declination = ka), and the eolian deposits that exhibit only Lower Chinle Group strata in west-central 271°, inclination = –17° (N = 10, α95 = 4.4°, κ = very weakly developed soils have been deposit- New Mexico and eastern Arizona comprise a 124). This tholeiite has higher K2O, TiO2, MgO, ed within the last millennia (<1 ka). The study 70–150-m-thick succession consisting of, in Co, Nb, Sr, Zr, and LREE contents than other area has experienced episodic eolian activity ascending order, the “mottled strata,” ZBVF tholeiites. The Candelaria Cluster com- throughout the Quaternary and is very close to Shinarump Formation, the Bluewater Creek prises four volcanoes within 4 km2 area that the threshold for eolian activity in the modern Formation and equivalents, and the Blue Mesa erupted alkalic and transitional lavas from an climate. Member of the Petrified Forest Formation. This asthenospheric source and tholeiitic lavas from succession rests disconformably upon the a lithospheric source. Lavas from all four vents Moenkopi Formation and is disconformably record moderate-amplitude paleomagnetic sec- HYDROLOGIC BUDGET ANALYSIS AND overlain by the Sonsela Member of the Petrified ular variation (declination = 32°, inclination = NUMERICAL SIMULATIONS OF Forest Formation. Stratigraphic data indicate 56°, N = 17, α95 = 2.8°, κ = 189) indicating erup- GROUND-WATER FLOW IN LOS ALAM- that as much as 100 m of stratigraphic relief was tion within a very short time span, conceivably OS CANYON NEAR LOS ALAMOS, NEW generated during development of the Tr-4 less than 100 yrs. MEXICO, by Robert Norman Gray, 1997, MS unconformity on the Blue Mesa Member. The ZBVF is located within the Basin and thesis, Department of Earth and Planetary Detailed lithostratigraphic work in the study Range/Rio Grande rift−Colorado Plateau tran- Sciences, University of New Mexico, area reveals that Adamanian (latest Carnian) sition zone, where extension has thinned the Albuquerque, NM 87131, 485 pp. localities are separated by as much as 100 m of crust and lithosphere with respect to the A hydrologic budget analysis for the Los stratigraphic section and that most of the strati- Colorado Plateau but not as much as in the Alamos Canyon watershed was prepared graphic succession here is of latest Carnian age. more highly extended Basin and Range. including annual budgets for the 1993, 1994, Numerous dinosaurs, including a new thero- Contemporaneous eruption of magmas from and 1995 water years and detailed budget cal- pod, from the Bluewater Creek Formation different mantle sources is consistent with a culations for the upper basin and demonstrate that dinosaurs were both diverse model in which transition-zone alkalic magmas middle/upper canyon areas covering nine sep- and derived in the latest Carnian. are generated at the boundary between arate stress periods from 7/10/94 to 11/2/95 upwelling depleted asthenosphere and residual corresponding to varying alluvial aquifer enriched lithosphere, and tholeiitic magmas are behaviors. Data sources included daily mea- PROTEROZOIC METAMORPHIC AND derived from the lithosphere. The lack of coher- surements of precipitation and snowpack TECTONIC EVOLUTION OF THE ent chemical trends among flows erupted from depths, streamflow discharge, and latent heat NORTHERN COLORADO FRONT different vents is interpreted to indicate that energy flux from which evapotranspiration RANGE, by Meghan Hodgins, 1997, MS the- each volcano erupted lavas evolved within sep- rates were determined. Average annual precip- sis, Department of Earth and Planetary arate magma chambers. Chemical variation itation rates over the watershed varied from Sciences, University of New Mexico, within each flow can be explained by fractiona- ~23 to ~31 inches during the analyzed periods. Albuquerque, NM 87131, 120 pp. tion of less than 5% each olivine and plagioclase The annual evapotranspiration component was The Proterozoic was a time of rapid crustal and less than 2% ilmenite, accompanied by less determined to represent between ~71% and accretion in southwestern North America fol- than 3% assimilation of local basement rocks. ~84% of the total budget. Annual infiltration lowed by an approximately 300 m.y. history of QUATERNARY EVOLUTION OF EOLIAN rates were calculated as residuals to the basic metamorphism and deformation. The accretion 72 August 1999 New Mexico Geology began approximately 1.75 b.y. ago along the nels and adjacent floodplains on an alluvial Tapicitos Member. Cheyenne Belt suture zone in southern slope. The Almagre and Largo faunas were corre- Wyoming. The region to the south of the suture Granulometric analyses were conducted for lated against