New Mexico graduate student abstracts New Mexico Geology recognizes the important research of graduate students working in M.S. and Ph.D. programs. The following abstracts are from M.S. theses and Ph.D. dissertations completed in the last 12 months that pertain to the geology of New Mexico and neighboring states.
New Mexico Institute of Mining USING HEAT AS A TRACER TO QUANTIFY quantify mixing relationships and identify sta- and Technology DAILY SURFACE WATER-GROUNDWATER tistically significant differences between water EXCHANGE IN THE EAST FORK JEMEZ types and data sets. RIVER, VALLES CALDERA, NM Multiple lines of evidence supported a close SOIL CHRONOSEQUENCE STUDY OF Paulino Céspedes, Eva R., M.S. connection between groundwater supplying LONG VALLEY, NEW MEXICO: INSIGHTS domestic wells and anthropogenic recharge INTO THE DEVELOPMENT OF SOILS Studying the temporal and spatial variations derived from acequias. Groundwater mounding ON PLEISTOCENE AND HOLOCENE of flow is critical to understand the fate and around the ditches produces a seasonal move- MORAINE CATENAS transport of solutes within hyporheic environ- ment of the groundwater table, corresponding Feldman, Anthony D., M.S. ments. Exchange fluxes can vary with time due with the yearly groundwater recharge cycle. to hydrologic drivers such as seasonal variability Water level variations observed in the alluvial The history of glacial advance and retreat cycles in regional groundwater flow and discharge aquifer varied significantly with the logarithm in mountain watersheds is recorded in glacial changes due to snowmelt and precipitation of distance from acequia, the well depth, landforms. The Sangre De Cristo mountain range events. From an observational perspective, and seasonal applications of flow allotments. in northern New Mexico contains some of the exchange fluxes and their dynamics can be Surface waters low in TDS and high in bicar- southernmost expansion of glacial activity in the estimated with the analysis of temperature time bonate are broadly distributed at these times, Southwest during the Quaternary but there have series collected within the stream sediments. In driven by infiltration of seasonal snowmelt and been few studies correlating its glacial chronol- this work, we explore the strengths and lim- peak streamflow. Geochemical mixing analysis ogy to the Rocky Mountain glacial record. itations of two analytical methods to estimate suggested that about 27% of the domestic Glacial deposits within Long Valley, a glaciated vertical exchange fluxes from temperature supply control-volume was mixed with water valley in the Sangre de Cristo Mountains, were time series. Both methodologies were sensitive recharged recently from the surface, and this correlated with the glacial history of the south- to sensor spacing, instrument resolution, and should be regarded as a minimum estimate. ern Rocky Mountains and Wind River Range magnitude and direction of the flux which Likewise, the heterogeneity of higher utilizing soil and landform properties. A soil resulted in overestimation, underestimation, or tritium values in the alluvial aquifer reflects profile development index (PDI) was calculated incorrect estimation of the velocity. The meth- that the groundwater recharge to the domestic utilizing soil texture, structure, consistency, and ods were used to estimate fluxes in the Jemez well supply derives significantly from vertical color data. Organic carbon, hydroxalamine River located in The Valles Caldera Natural infiltration out of the acequia system. Some extractable (FeO) and dithionite extractable Preserve, NM, which served as an example of wells access mixtures more strongly supplied (FeD) iron oxides, and clay accumulation were a typical low-gradient, meandering mountain by long-residence time recharge from the also utilized to differentiate moraine age correla- stream where temporal and spatial variability mountain block that has flowed across the tions. Soil development is observed to increase of vertical exchange fluxes were analyzed along Sangre de Cristo Fault (SDCF). Groundwater with age between soil catenas and at individual a riffle-pool-riffle sequence reach. Vertical fluid signatures of the endmembers show that solutes catenary positions. Utilizing the calculated PDI velocities varied from –1 to 1 m/d and ground- derived from primary chemical weathering of values, chemical and physical proxies, as well water-surface water exchange was attributed to the Latir Peak Volcanic Field have the largest as field and DEM observations of moraine pressure gradients due to the topography of the mixing fraction just west of the SDCF. Calcium morphology, four Pleistocene glacial periods streambed, local groundwater flow systems, and is associated with high sulfate in the ambient are observed within the Long Valley moraine localized small lateral flow paths originated at geological system, reflecting the presence of sequence as well as two smaller rock glacier and the meander bends. gypsum in the caldera source watershed. The peri-glacial periods during the Holocene. These areas dominated by the two major background cycles were correlated to the Bull Lake, Pinedale, groundwater types, bicarbonate and sulfate, are Oldest Dryas, Youngest Dryas, and two periods HYDROGEOLOGY OF THE QUESTA AREA: found downgradient of the regions of recharge during the latter half of the Holocene. Among END MEMBER MIXING ANALYSIS OF through alkaline rock types and metaluminous moraine morphology parameters, summit width SHALLOW GROUNDWATER bodies respectively. This pattern requires signifi- and flank slope best distinguished moraines of Robinson, Kylian, M.S. cant subsurface connectivity across Quaternary different ages. Profile mass content of FeD iron normal faults of the eastern rift. and clays increased with age while FeO iron and In order to understand a pattern of seasonal In the volcanic aquifer, longer-residence organic carbon profile mass content decreased well failures at Questa, New Mexico, we devel- groundwater flow predominates. Small but with age. The soil PDI chronofunction had oped an endmember mixing analysis (EMMA) consistent declines in the head of the volcanic the highest correlation with the glacial age model that embraces the small scale geological aquifer amounting to 0.14 feet/ year were determinations, with chronofunctions for clay complexities of the northern Rio Grande Rift. measured over the course of our study. Head and the FeO/FeD ratio also representing good Geochemical measurements from multiple levels in this region do not respond significantly age discriminators. organic carbon, FeO, and datasets were compared to quantify the connec- to seasonal forcing, except where the aquifer FeD iron were not as useful in differentiation tion of surface water with the mountain block is overlain and partially confined by saturated of moraine ages. Chronofunctions for catenas aquifer with the alluvial aquifer, and the alluvial alluvium. Identification of the key distinguishing and moraine summits possessed the best age aquifer with the volcanic aquifer. tracer boron at the Dacite Fault Zone crosscut- correlations, while toeslope chronofunctions did Wells and springs were sampled once for ting Guadalupe Mountain establishes that the not correlate well with age. major ions, trace metals, water and sulfur volcanic aquifer receives measurable inflow isotopologues, and age tracers 14C and 3H, from a deep-circulating hydrothermal system. while hydraulic head was measured seasonally Groundwater flow converges on the volcanic throughout the course of three years. These data complex from northeast to east, as far north as were analyzed under the rubric of EMMA to Latir Creek West and as far east as the alluvial
Spring 2019, Volume 41, Number 1 44 New Mexico Geology valley where the Red River emerges at the SDCF. stratigraphy and 36Cl ages imply climatic con- Grande and routes through typical formations These cool and chemically variable waters mix trols on river incision from terraces that have found in the middle Rio Grande Valley. Two thoroughly with upwelling fluids, creating a surface-exposure ages of 26–29, 64–70, and 135 years of observations reveal a channel that geochemically homogeneous solute composition ka. Carbon-14 ages from detrital charcoal show floods 3–5 times a year from summer mon- in the volcanic aquifer. We conjecture that the that the most recent aggradation event persisted soon rains. Rainfall and water depth were observed aquifer head decline results from until at least 3 ka during the transition from gla- recorded continuously at two locations in the decreasing streamflow and watershed discharges cial to modern climate conditions. Our terrace watershed. According to these instruments, a observable at gaging stations that bracket the chronology supports existing climate-response minimum rainfall intensity of 3.5 mm/15min Red River Spring Zone (RRSZ). models of terrace formation in arid environ- is required to generate runoff, regardless of Contaminant loading from the tailings ments and links tributary responses to the axial location in the basin. Water depth, velocity, impoundment into the RRSZ and elsewhere Rio Grande system throughout the central Rio and vertically integrated suspended sediment within the groundwater system increased Grande rift. Soil characteristics from dated ter- samples were collected at the basin outlet. In in recent years (-2017) despite cutbacks in race surface provide rates of dust and carbonate total, 35 suspended sediment and 180 depth and mine-dewatering discharges to the tailings accumulation for durations of 0.5-800 kyrs. Soil velocity measurements were collected from nine impoundment. We identify two tailings leachate development in arid and semiarid regions of the events. A rating curve was developed using the endmembers, one oxidizing and rich in uranium, southwestern United States is predominantly discrete depth and velocity measurements and the other more reducing and high in molybde- controlled by influx of eolian dust. I use the the resulting calculated discharges are used to num, that correspond with samples from highly 36Cl and 14C soil ages presented in Chapter 2, compare the suspended sediment concentration productive and poorly productive extraction coupled with soil textures and the profile devel- (SSC) between samples. SSC ranged from 4,040 wells, respectively. The EMMA model tends opment index (PDI), to estimate rates of soil mg/L to 74,000 mg/L. Samples collected during to under-predict mixing ratios compared with development in the Socorro area. The silt-and- the falling limb of the hydrograph were well values derived from only the most mobile clay and profilemass carbonate contents of the correlated to discharge (r2 = 0.72) while samples tracers and molybdenum. Ongoing changes in soils increase with soil age and yield power-law collected during the rising limb were moderately contaminant levels at the monitoring sites result slopes of 0.33–0.34. The PDIs also increase at correlated (r2 = 0.39). from at least two independent causes. 1) Mixing rates of 0.33 with increasing soil age and can Prior to the third year of study, a new sed- relationships can be temporally variable because be used to roughly estimate the ages of undated iment monitoring station was completed near surfacewater infiltration varies each year soils. The rate of soil development in the Socorro the Piños watershed outlet. The new station with watershed yield. 2) Contaminant retar- area is less than that estimated for soils in higher includes seven different methods of measuring dation due to ion exchange reactions in the latitude regions of New Mexico, but is roughly bedload and three methods to measure sus- subsurface becomes exhausted at some point similar to that estimated for soils farther south. pended load. Direct measurements of bedload in the aquifer, allowing progression of This may be due in part to a regional climate are collected using Reid-type slots samplers contaminants downstream. gradient presently manifested by greater mean while direct measurements of suspended are col- Changes in the contaminant plume can annual precipitation and cooler mean annual lected using automated water samplers. These be more precisely mapped by including some temperatures at higher latitudes and/or slower direct measures are used to calibrate a host of additional selected constituents in the analytes rates of eolian dust accumulation into the soil surrogate technologies including microphones, of the monitoring program, such as water iso- profile. Rio Salado terraces preserved at the sur- geophones, seismometers, and hydrophones. topologues, boron, silica, and lithium. Sampling face and above the Socorro magma body (SMB) Few ephemeral channels are studied worldwide should be regularized to correspond with high provide paleo-geodetic markers to interrogate and no ephemeral channel has been studied and low infiltration seasons, in order to properly the longevity of magmatism in the Socorro area. more than the Nahal Eshtemoa in the Negev assess the different contributions of mixing and High-resolution elevations from Rio Salado desert in Israel. Sediment transport dynamics in retardation to our observations. With a larger terraces that cross surface-uplift contours the channel have been studied for over 25 years. sample size and better-constructed covariance document a prehistoric surface-uplift event Plate microphones, a surrogate technology groups to support the mathematics, background above the SMB. Longitudinal terrace patterns to measure bedload flux, are calibrated in the values and anthropogenic changes alike can be are consistent with an arching event that began Eshtemoa. Two methods of calibration were modeled with greater confidence. after 26 ka and ceased before 3 ka and cannot tested: a time-averaged method which has been be explained by tectonic or fluvial mechanisms. traditionally used, and a mass-averaged method This late Pleistocene-early Holocene surface which is new to calibration in the Eshtemoa. The GEOMORPHIC HISTORY AND uplift is related to a magma-emplacement mass-averaged method is shown to be better in CHRONOLOGY OF QUATERNARY event that predates modern magmatism and is almost every way. It is more robust, particularly ALLUVIAL DEPOSITS IN THE SOCORRO collocated with geodetic uplift. The two tempo- at lower transport rates, it is effective at all flood AREA, CENTRAL RIO GRANDE RIFT, NEW rally distinct surface-uplift events likely record stages (rise, max, and fall of the hydrograph), MEXICO episodic intrusion below the Socorro area since and it is more consistent across events. Sion, Bradley D., Ph.D. late-Pleistocene time. Magmatic activity may be rejuvinated via a stationary plumbing system Fluvial terraces in the central Rio Grande rift inferred from seismic data. This study shows INFLUENCE OF LITHOLOGY AND record important Quaternary climatic and that the magmatic source-feeder system is stable DIAGENESIS ON MECHANICAL AND tectonic signals. Age control among Rio Grande and active over timescales of 104 yrs and demon- SEALING PROPERTIES OF THE terrace sequences in central and southern New strates the utility of terraces as strain markers of THIRTEEN FINGER LIMESTONE AND Mexico is limited, so regional correlations low-amplitude, large-wavelength deformation UPPER MORROW SHALE, FARNSWORTH are unreliable and important process-related caused by mid-crustal magmatic activity. UNIT, OCHILTREE COUNTY, TEXAS questions about the mechanisms and rates Trujillo, Natasha Andrea, M.S. controlling terrace formation and deformation A TWO-YEAR STUDY OF FLASH FLOOD cannot be addressed. I present a terrace chronol- CHARACTERISTICS IN NEW MEXICAN This thesis focuses on an evaluation of the ogy from the central New Mexico Socorro AND ISRAELI EPHEMERAL CHANNELS caprock for a commercial-scale carbon storage Basin from 36Cl surface-exposure and 14C ages Stark, Kyle, M.S. project at the Farnsworth Unit (FWU) in Texas. to establish a firm foundation for Socorro Basin The FWU is currently in the injection phase of terrace stratigraphy, provide terrace correla- The Arroyo de los Piños has been chosen as a this Southwest Regional Partnership for Carbon tions to adjacent rift basins, and test climate prime location to study sediment flux in New Storage (SWP) project, and the goal is to inject response models of terrace formation. Terrace Mexico. It is a direct tributary of the Rio 1 million metric tons of anthropogenic CO2 into
Spring 2019, Volume 41, Number 1 45 New Mexico Geology the Morrow B sandstone reservoir. The main at the boundary between caprock and reservoir CRUSTAL DEFORMATION RELATED TO lithologies within the caprock are mudstone, is predicted to behave in a ductile fashion, and is EMPLACEMENT OF THE SOCORRO cementstone, and some coal. The mechanical therefore not conductive to creation of fracture MAGMA BODY properties of these lithologies, along with an bypass systems. Seal bypass from existing fault/ Yao, Shuoyu, M.S. understanding of the diagenetic history of each fracture reactivation is the largest threat to this lithology, help determine how the caprock caprock system. If the operator of FWU contin- The Socorro magma body is the second-largest will react to stress perturbation resulting from ues to stay below the fracture gradient for the known crustal magma body on Earth. It covers elevated pore pressure due to injection of super- caprock, then there should be no issue with loss 3400 square kilometers, has a thickness of critical CO2 into the underlying reservoir. of seal integrity. ~130 m, and is situated at 19 km depth below The principal objective of this work is the surface. The magma body is located within to understand the lithologic and diagenetic the Rio Grande rift zone, in the crust below the controls on mechanical attributes of the ESTIMATION OF FOCUSED RECHARGE southern Albuquerque basin, the Socorro basin, caprock. Important diagenetic processes that FOR NEW MEXICO USING A SOIL-WATER- and the accommodation zone connecting these have affected the rock include: carbonate pre- BALANCE MODEL: PYRANA two basins. Previous surface-leveling and InSAR cipitation, as concretions and possibly laterally Xu, Fei, M.S. studies suggest that the Socorro magma body is extensive cementstone layers, as well as fracture still active; causing surface uplift with a maxi- fills. The fracture fills are commonly fibrous -cal Determining the rate and distribution of mum rate of 2.5–3.0 mm/year centered around cite “beef” filling subhorizontal fractures. These groundwater recharge helps in water planning, San Acacia, New Mexico. The Socorro seismic may have formed during an overpressurization sustainable development in the future, and pre- anomaly is a seismically very active region of event and are found throughout the Thirteen venting contaminants from entering the aquifer. mainly upper crustal earthquakes above the Finger Limestone. The carbonate cementstone Regional statewide in-place groundwater diffuse magma body. lithology within the Thirteen Finger Limestone recharge estimation has been attempted by using In this study, Socorro magma body emplace- is largely authigenic and was sampled from the a distributed-parameter soil-water-balance ment processes are studied, constrained by the core in grid patterns to infer lateral continuity. model that simulates recharge on the daily sill-related surface uplift and seismicity patterns. Because most of the grids have an asymmetric time-step at a resolution of 250 x 250 m. The I use the general finite-element software package shape, the layers may be laterally extensive. model, which is called the Evapotranspiration Abaqus® to build models of crustal deforma- However, it cannot be ruled out that some of and Recharge Model (ETRM), used gridded tion. The fundamental analysis method used for the “layers” are part of larger concretions. The precipitation, reference evapotranspiration, and all experiments is a fully-coupled thermal-stress elastic properties of all the different lithologies soil property data as the main inputs. Because analysis, in which results from thermal analysis within the caprock can be used to determine focused recharge (i.e., transmission loss in depend upon displacement results and vice the brittle/ductile nature of these rocks. The ephemeral channels) is an important contributor versa. The 2-D elastic models are composed cementstone is the most brittle lithology within to groundwater recharge in semiarid-to-arid of two parts: the crustal block, and the sill the caprock, whereas the mudstones are the environments, a stochastic rainfall-runoff gener- which is embedded into the crustal block at most ductile. Fracture analysis of the core from ation algorithm was developed to substitute for 19 km depth. Surface uplift above the Socorro the characterization wells constrain paleo-stress the original Hortonian overland flow scheme magma body is caused by thermal expansion of conditions and induced fractures from the core in the ETRM runoff generation procedure. the crustal material and/or a direct effect from helped determine current stress conditions The change in the core algorithm of the ETRM inflation of the sill (magma addition). The two within the subsurface. Determining the three made the model able to incorporate both diffuse effects, thermal and mechanical, are both also principal stress orientations and magnitudes recharge and transmission losses in the first-or- modeled separately to understand their individ- help predict critically oriented fractures and der basin scale into the statewide recharge esti- ual contributions, and combined in one model. faults that could reactivate from injection mation. Thus, Python Recharge Assessment for The models predict thermal evolution, crustal of CO2. New mexico Aquifers (PyRANA) is proposed to deformation, and associated stresses. Determining seal potential for the FWU be a more appropriate name for the new version The modeling results show the following involved evaluation of seal geometry, capacity, of the ETRM model. PyRANA results show crustal evolution upon sill emplacement: (1) A and integrity for the upper Morrow Shale and high recharge in the mountainous areas and the thermal aureole develops around the sill, result- the Thirteen Finger Limestone. The mudstone karst landscape of the state up to about 20% ing in thermal expansion. The uplift pattern lithologies overlying the fluvial reservoir facies of annual precipitation. The rest of the semiarid caused by thermal expansion during the sill are marine in origin and the cementstones are part of the state recharged around 4% of annual emplacement phase is wider, and the uplift rate of diagenetic origin. As the caprock covers the precipitation. Arid parts of the state received lit- is larger, than the observed uplift pattern; (2) sandstone reservoir, which is laterally restricted tle in-place recharge. PyRANA recharge results After cooling of the emplaced sill starts, surface by deposition in a paleo-valley, the caprock lith- are close to previous point studies conducted in uplift rates are at least an order of magnitude ologies are laterally extensive enough to form southern New Mexico. The amount of focused smaller than observed uplift rates, and are below an effective trap. Therefore, the principal issues recharge at larger scales (2nd to 3rd order streams InSAR detection limits; (3) Net uplift caused by related to the ability of the caprock to inhibit the and higher) can be calibrated on the watershed sill inflation is an approximately linear function upward migration of petroleum and CO2 are basis by comparing PyRANA runoff and flume of magma overpressure; (4) The temperature the sealing capacity of the caprock lithologies, records. The rainfall-runoff generation regime evolution suggests that the sill solidifies on and the likelihood of any seal bypass features, was developed using data from the Walnut a time scale of a few hundred years after an such as interconnected fracture networks. Gulch Experimental Watershed, which is under injection event; (5) Sill inflation causes crustal With the above constraints, I conclude that a semiarid to arid climate setting. Therefore, stresses, with a zone of horizontal compression the seal capacity is excellent for the principal future work should focus on validating PyRANA directly above the sill, and horizontal tension caprock lithologies. by adding statistical analysis of rainfall-runoff between ~13 km depth and Earth’s surface; (6) Understanding geomechanical properties of generation procedure in the mountainous areas. The average surface uplift rate during one heat- the caprock and attendant fracture gradients ing-cooling cycle of the sill emplacement due to help constrain the maximum injection pressure the combined effect of thermal expansion and possible without fracturing, as well as the inflation is similar to the observed uplift pattern. likelihood of seal bypass. The maximum pore Based on these results, I develop a new model pressure that can be attained at the reservoir/ for Socorro magma body emplacement. Because caprock interface without fracturing the caprock a newly emplaced sill cools down rapidly to is 6518 psi (44.9 MPa). The caprock lithofacies temperatures below those associated with
Spring 2019, Volume 41, Number 1 46 New Mexico Geology the formation of a crystal mesh, the currently peak age of 1706 Ma with a secondary peak at minimal evidence for subduction contributions, imaged fluid sill must be younger than several 1451 Ma (northern Uncompahgre uplift). Two and instead represent decompression melts hundred years, or, if it is older, a significant samples in southern New Mexico exhibit no pri- of an enriched sub-arc mantle. Along the arc, magma injection event must have occurred mary peaks, but have a wide range of ages from subduction component contributions appear in the last few hundred years to maintain the 270–3106 Ma, and are both locally and distally to decrease from south to north. There is also molten status of the sill. The ongoing seismicity sourced (Pedernal, Uncompahgre uplifts). a change in mantle source enrichment along the above the sill is interpreted to result from injec- Data support a model in which the arc, with magmas from central Oregon deriving tion events, which stress the crust so that slip Uncompahgre, Sierra Grande, and Pedernal from a more enriched mantle than those from along favorably oriented faults occurs. If this is uplifts in New Mexico were actively contrib- northern California and southern Oregon. true, magma injection occurs every 5–10 years uting sediment during the Early Permian, while It also appears that subduction component or so, concurrent with seismic swarms. The cur- the Defiance-Zuni and Peñasco uplifts were contributions may have decreased over time, rent surface uplift above the sill results from sill inactive and onlapped before the end of Abo while mantle source enrichment, at least in inflation, and longer-term thermal expansion. deposition. Fluvial systems flowed from north central Oregon, may have increased. Although to south, and drainage networks were complex the Cascades are a “hot” subduction zone, this and interconnecting, transporting sediment thesis finds that both magmas with evidence for New Mexico State University from central Colorado to southern New Mexico subduction contributions (CAB, LKT) and those by the Early Permian. without (IPB) are erupted within the arc and that subduction contributions to CAB and LKT PROVENANCE AND SEDIMENT magmas decrease northward along the arc. DISPERSAL TRENDS FROM EARLY EVALUATING ALONG-ARC TRENDS IN PERMIAN (WOLFCAMPIAN) NONMARINE SUBDUCTION CONTRIBUTIONS TO THE STRATA OF THE ABO FORMATION (AND SOUTHERN CASCADES: INSIGHTS FROM INFLUENCE OF INHERITED CRUST ON AGE-EQUIVALENT STRATA) IN NEW BASALTIC MAGMA GEOCHEMISTRY THE MAZATZAL PROVINCE INTRUSIVE MEXICO Cole, Meredith, M.S. ROCKS: EVIDENCE FROM ZIRCON Bonar, Alicia L, M.S. XENOCRYSTIC CORE AGES AND ISOTOPE The Cascade arc is a continental volcanic arc, GEOCHEMISTRY The Early Permian (Wolfcampian) nonmarine, extending from northern California to British Howland, Colby R., M.S. clastic strata of the Abo Formation (and Columbia, formed by subduction of the Juan age-equivalent strata) record the final stage of de Fuca plate and the Gorda and Explorer U-Pb geochronology, zircon Hf isotope compo- synorogenic sedimentation associated with the micro-plates under the North American plate. sitions, whole-rock geochemistry, and geologic Ancestral Rocky Mountain orogeny (ARM) The traditional model for generating arc mapping were used to understand the formation in New Mexico. During this time, ARM magmas requires mantle melting resulting from of the Mazatzal province in southern New deformation was characterized by at least eight fluid-fluxing of the mantle with a “subduction Mexico and provide insight into lithospheric basement-block uplifts that exposed a number component” consisting of H O-rich fluids and/ crustal growth during the Paleoproterozoic. The of Proterozoic basement provinces throughout 2 or melts (e.g., Plank and Langmuir, 1993; Plank data indicate three pulses of Paleoproterozoic southwestern Laurentia. Sandstone modal et al., 2005). In a “hot slab” subduction zone, magmatism occurred in southern New Mexico composition trends and U-Pb detrital zircon such as Cascadia, the subducting slab is young at 1675 Ma, 1655 Ma, and 1630 Ma. These geochronology from these strata provide a basis and relatively hot, such that complete dehy- pulses of magmatism formed during different for constraining uplift history and detrital con- dration of the slab should occur in the forearc, tectonic regimes. 1675 Ma igneous rocks are tributions from basement blocks to create a new leading to a reduced capacity for fluid-flux pervasively deformed felsic gneisses with more sediment dispersal model for the Early Permian melting of the sub-arc mantle wedge (Syracuse evolved Hf isotopes ( Hf=+4.3) and contain stage of ARM orogenesis in New Mexico. ε et al., 2010). However, basalts with elevated xenocrystic (1737 ± 16 Ma and 1778 ± 13 Ma) Sandstone modal composition for the H O contents and trace element compositions zircon cores suggesting a component of recycling Abo Formation (and age-equivalent strata) is 2 consistent with subduction component contri- of Yavapai-age crust or sediment during their dominated by quartz and feldspar grains, with butions are associated with volcanoes in the formation. Through time, Mazatzal-age plutons rare lithic fragments (Q=56%, F=42%, L=2%). southernmost arc as well as monogenetic vents show an increase in their apparent 176Lu/177Hf Northern samples contain a majority of the in central Oregon (Grove et al., 2002; Leeman et ratios, indicating the progressive mixing of potassium feldspar grains (K=19%), and there al., 2005; Ruscitto et al., 2010; Ruscitto et al., juvenile lithosphere with older evolved crust. is an absence of potassium feldspar in southern 2011; Walowski et al., 2016). Segmentation of Field relationships and U-Pb ages suggest that samples (K
Spring 2019, Volume 41, Number 1 47 New Mexico Geology University of New Mexico spacing makes it possible to detect these arrivals, arrival of the Virgin River across the Virgin which likely occur due to the strong impedance Mountains to a maximum depositional age NEW GEOCHEMICAL AND ISOTOPIC contrast between the rift basin sediments and of 5.9 Ma. Incision magnitudes and rates of APPROACHES TO SHALLOW CRUST bounding basement-cored fault blocks. the Virgin River show a stair-step increase in LANDFORM EVOLUTION bedrock incision as the river crosses multiple Decker, David, Ph.D. N-S trending normal faults. Average calculated A SPELEOTHEM RECORD OF CLIMATE rates are 23 m/Ma in the Lake Mead block, Many researchers have studied the Guadalupe VARIABILITY IN SOUTHWESTERN 85 m/Ma in the combined St. George and Mountains in detail and starting with King NORTH AMERICA DURING MARINE Hurricane blocks, and 338 m/Ma in the Zion (1948), many of them have speculated about ISOTOPE STAGE 3 block. Block-to-block differential incision adds the timing of the uplift of the Guadalupe block. Peinado, Justin G., M.S. cumulatively such that the Zion block has been There are several competing hypotheses includ- deeply incised ~1 km (~315 m/Ma) over 3.6 ing Laramide, Basin and Range, and Rio Grande During Marine Isotope Stage 3 (MIS-3) of the Ma relative to the Colorado River confluence. Rifting uplift scenarios. Using uranium-lead last glacial period, there were rapid transitions We test two hypotheses: 1) observed differential dating of scalenohedral spar found in small vug between warm and cold climates referred incision magnitudes and rates along the Virgin caves throughout the study area, I have dated the to as Dansgaard-Oeschgerr (DO) events. In River system are a measure of mantle-driven dif- episodes of spar formation to two major phases, Southwestern North America (SWNA), two ferential uplift of the Colorado Plateau relative 36 to 33 Ma and 30 to 27 Ma. These two epi- speleothem paleoclimate records document to sea level over the past ~5 Ma. 2) Observed sodes of spar formation are in good agreement changes in moisture source delivery in response differential river incision relates to river inte- with the time frame of the ignimbrite flare up to DO-events during MIS-3, but do not gration across previously uplifted topography during the formation of the Basin and Range. address potential changes in effective moisture and differential rock types with no post 5 Ma I have also dated several older phases, all the for the region. In this study, we introduce a uplift. Strong correlations exist between high way back to ~180 Ma, which all correspond to new high-resolution speleothem paleoclimate channel steepness (ksn) and low mantle veloci- nearby (<100 km) known volcanic activity and record from Carlsbad Cavern in the Guadalupe ties throughout the Virgin River drainage while provide a good argument for the hydrothermal Mountains. The speleothem, sample BC-5, grew weaker correlations exist between high ksn and genesis of the spar. By determining the depth of continuously from 46–31 kya during the latter resistant lithologies. Basaltic volcanism, which formation of the spar through a new speleoge- half of MIS-3, based on U-Th dating. We also has migrated at a rate of ~18 km/Ma parallel tied stable isotope (δ18O and δ13C) and trace to the Virgin River between ~13 and 0.5 Ma netic model (supercritical CO2), age dating the cave spar through U-Pb dating techniques, and element (Sr/Ca, Mg/Ca, and Ba/Ca) analysis to suggests a possible mantle-driven mechanism finding the temperature of formation of the spar the U-series chronology to produce multiple for the combined observations of differential through a newly calibrated δ88Sr thermometer high-resolution time-series. Our data further uplift across faults and additional young and fluid inclusion assemblage analysis, I have strengthens the shifting westerly storm-track Colorado Plateau epeirogenic uplift tracked by been able to develop a thermochronometer in a hypothesis and suggest that DO-events led to headward river propagation. Thus, we interpret region that has not had the typical apatite fis- changes in effective moisture. The stable isotope the Virgin River to be a <4.5 Ma disequilibrium sion track and apatite thorium-helium methods time-series displays DO-events and are clearly river system responding to ongoing upper man- available. Using this new method, along with tied to other speleothem records from SWNA tle modification and related basalt extraction, U-Pb dating of calcite vein spar from the Border and the NGRIP ice core record. When compared which is driving ~1 km of young uplift of the Fault Zone, I have constrained the timing of the to a Holocene speleothem record (BC-11) and a western Colorado Plateau. uplift of the Guadalupe block to between 27 and speleothem Asian Monsoon record, it becomes 16 million years. apparent that δ13C is a record of local changes in effective moisture and vegetation. δ13C also GLOBAL SEAWATER REDOX TRENDS
suggests an atmospheric ρCO2 control on veg- DURING THE LATE DEVONIAN MASS DENSE-ARRAY TELESEISMIC IMAGING OF etation and speleothem calcite during the last EXTINCTION DETECTED USING THE SOUTHERN ALBUQUERQUE BASIN glacial as has been suggested in other studies. U ISOTOPES OF MARINE CARBONATES Finlay, Tori S., M.S. Trace element analysis of BC-5 further supports White, David A., M.S. the stable isotope interpretations. Sr/Ca, Mg/Ca, The southern Albuquerque basin is a complex and Ba/Ca all strongly covary, indicating that The Late Devonian extinction ranks as one of the area of high extension, multiple orogenies, they are controlled by similar processes, and are ‘big five’ Phanerozoic extinctions affecting up to and ongoing uplift from a midcrustal magma likely connected to changes in effective moisture 80% of marine species and occurred during five body in which geophysical coverage is sparse. and local karst processes. distinct pulses spanning /or widespread marine In this thesis, I capitalize on recent innovations anoxia. We test the marine anoxia hypothesis in dense-array processing techniques to create by analyzing uranium isotopes (δ238U) across a virtual source reflection profiles from five BIRTH AND EVOLUTION OF THE VIRGIN ~7 My interval of well-dated Upper Devonian teleseismic events during the deployment of RIVER: ~1 KM OF POST-5 MA UPLIFT OF marine carbonates from the Devil’s Gate the Sevilleta array. The Sevilleta array consisted THE WESTERN COLORADO PLATEAU Limestone in Nevada, USA. of ~800 vertical component nodes with ~300 Walk, Cory J., M.S. The measured δ238U curve shows no m spacing deployed for 10 days in February co-variation with local anoxic facies, water- of 2015. Virtual source reflection profiles are The uplift history of the Colorado Plateau has depth dependent facies changes, redox-sensitive created by using the free surface of the earth been debated for over a century with still no uni- metals, TOC, or diagnostic elemental ratios as a virtual seismic source, yielding profiles fied hypotheses for the cause, timing, and rate indicating the δ238U curve was not controlled by that mimic active source seismic surveys. From of uplift. 40Ar/39Ar dating of semi-continuous local depositional or diagenetic processes and the seventeen virtual source reflection profiles basaltic volcanism over the past ~6 Ma within represents global seawater redox conditions. created, I am able to resolve mapped and buried the Virgin River drainage system, southwest Two negative δ238U shifts (indicating more geologic structures throughout much of the Utah and southern Nevada, provides a way to reducing seawater) are observed with durations southern Albuquerque and northern Socorro calibrate differential river incision and compare of ~3.8 My (late Frasnian) and ~1.1 My (early basins. Furthermore, I present a unique case of patterns of basaltic migration, mantle velocity Famennian), respectively. Steady-state modeling teleseismic P-wave to Rayleigh wave conversion, structure, channel steepness, lithology, incision of the observed -0.2 to -0.3‰ shifts in δ238U which is a dominating feature along the western history and the birth and evolution of the Virgin points to a ~5–15% increase in the total area margin of the two basins. The dense instrument River. New detrital sanidine ages constrain the of anoxic seafloor during these excursions. The
Spring 2019, Volume 41, Number 1 48 New Mexico Geology late Frasnian negative shift is broadly coincident with the first extinction pulse (late rhenana Zone or lower Kellwasser event), whereas the early Famennian negative shift (lower-middle triangularis zones) does not coincide with the most intense Frasnian-Famennian boundary (F-F) extinction pulses (upper Kellwasser event). Compilations of local sediment redox condi- tions from Upper Devonian marine deposits with conodont zone-level age control indicates that the extinction pulses were coincident with widespread anoxic deposits accumulating in subtropical epeiric sea and some open-ocean settings supporting previous interpretations that widespread marine anoxia had an important influence on the Late Devonian extinction. The temporal relationships between global ocean redox trends represented by the δ238U curve and the newly compiled subtropical marine redox sediment trends indicates Late Devonian global oceans and epeiric seas were in relatively good redox communication for the majority of the study interval except for a brief interval (<500 ky) spanning the F-F boundary.
Spring 2019, Volume 41, Number 1 49 New Mexico Geology