Geochemistry Commons^™

Adaptive Management In Native Grasslands Managed By The U.S. Fish And Wildlife Service—Implications For Grassland Birds, Lawrence D. Igl, Welsey E. Newton, Todd A. Grant, Cami S. Dixon

United States Geological Survey: Publications

Burning and grazing are natural processes in native prairies that also serve as important tools in grassland management to conserve plant diversity, to limit encroachment of woody and invasive plants, and to maintain or improve prairies. Native prairies managed by the U.S. Fish and Wildlife Service (FWS) in the Prairie Pothole Region of the northern Great Plains have been extensively invaded by nonnative, cool-season species of grasses. These invasions were believed to reflect a common management history of long-term rest and little or no defoliation by natural processes (burning and grazing). To address the challenges associated with these invasive species, …

Bonneville Basin Data, Larry V. Benson

United States Geological Survey: Datasets

In the Bonneville Basin folder, all data were reported in: Benson, L.V., Lund, S.P., Smoot, J.P., Rhode, D.E., Spencer, R.J., Verosub, K.L., Louderback, L.A., Johnson, C.A., Rye, R.O., Negrini, R., 2011. The rise and fall of Lake Bonneville between 45 and 10.5 ka. Quaternary International 235: 57-69.

http://digitalcommons.unl.edu/usgsstaffpub/726

General Comment: in most cases an age model based on ¹⁴C analyses is not included with the data sets although ones were created for the original publications. Given the general problems with ¹⁴C ages in the lakes of the Great Basin, age models based on paleomagnetic secular variation (PSV) are …

Nuclear Weapons In A Changing Climate: Probability, Increasing Risks, And Perception, Adam Liska, Tyler R. White, Eric Holley, Robert J. Oglesby

Adam Liska Papers

Many people tend to think that the outcome of any nuclear weapons use today will result in an escalatory situation with apocalyptic outcomes for the countries involved. Yet many factors are increasing the probability of the limited use of nuclear weapons (e.g., 1 to 20 warheads) in a range of conflict scenarios. Previous atmospheric model simulations of regional nuclear conflicts employing many relatively small bombs have been estimated to cause a global “nuclear autumn,” with great reductions in agricultural productivity, stratospheric ozone loss, and spread of hazardous radioactive fallout. The totality of these effects would result in widespread damage …

Mono Lake Data, Larry V. Benson

United States Geological Survey: Datasets

Mono Lake Basin Data\ Depth CalAge TIC TOTC TOC 13C 18O

Mono Lake short cores.xlsx 03.03.2014 19:59:44 0.06 xlsx

Depth PSV age 18O 13C

TIC for Wilson Crk Fm.xlsx 02.03.2014 16:07:10 0.03 xlsx

Ostracode 18O and TE data Wilson Crk Fm.xlsx 10.11.2017 17:43:18 0.12 xlsx

Depth, calendar age, TIC, TOTC, TOC, ¹³C, and ¹⁸O of Mono Lake short cores were reported in:

Benson, L., Linsley, B., Smoot, J., Mensing, S., Lund, S., Stine, S., and Sarna-Wojcicki, A., 2003, Influence of the Pacific Decadal Oscillation on the climate of the Sierra Nevada, California and Nevada: Quaternary Research. Quaternary Research …

Summer Lake Basin Data, Larry V. Benson

United States Geological Survey: Datasets

Summer Lake Basin

Name Date modified Time modified Size MB Extension

Summer Lake Basin\

Depth PSV Age 13C 18O Summer Lake B&B core.xlsx 03.03.2014 16:51:12 0.03 xlsx

In the Summer Lake Basin folder:

Depth, PSV age, ¹⁸O, ¹³C data for Summer Lake core B&B are reported in:

Benson, L., Lund, S., Negrini, R., Linsley, B., and Zic, M. 2003. Response of North American Great Basin lakes to Dansgaard-Oeschger oscillations. Quaternary Science Reviews 22: 2,239-2,251.

General Comment: In most cases an age model based on ¹⁴C analyses is not included with the datasets although ones were created for …

Great Basin Surface Water And Precipitation Isotope Data, Larry V. Benson

United States Geological Survey: Datasets

In the Great Basin Surface Water and Precipitation Isotope Data folder:

Farad, Nixon, and Pyramid Lake 18O data were reported in:

Benson, L.V., 1994, Stable isotopes of oxygen and hydrogen in the Truckee River-Pyramid Lake surface-water system. 1. Data analysis and extraction of paleoclimatic information: Limnology and Oceanography, vol. 39, p. 344-355. https://digitalcommons.unl.edu/usgsstaffpub/1015

Spring chemistry around Pyramid Lake data were reported in:

Benson, L.V., 1994, Carbonate deposition, Pyramid Lake subbasin, Nevada: 1. Sequence of formation and elevational distribution of carbonate deposits (tufas): Palaeogeography, Palaeoclimatology, Palaeoecology, vol. 109, p. 55-87.

Benson, L.V., Kashgarian M., and Rubin, M., 1995, Carbonate deposition, …

Owens Lake Core Data, Larry V. Benson

United States Geological Survey: Datasets

In the Owens Lake core data folder:

¹⁴C ages for cores OL84 and OL90 were reported in:

Benson, L.V., Burdett, J.W., Kashgarian, M., Lund, S.P., Phillips, F.M., and Rye, R.O., 1996, Climatic and hydrologic Oscillations in the Owens Lake basin and adjacent Sierra Nevada, California: Science, vol. 274, p. 746-749.

Benson, L.V., 1999, Records of millennial-scale climate change from the Great Basin of the Western United States: In Clark, P., Webb, R., Keigwin, L., eds., Mechanisms of Global Climate Change at Millennial Time Scales, American Geophysical Union Monograph 112, p. 203-225.

Benson, L., 2003, Western Lakes: Chapter 9 in …

Paleomagnetic Secular Variation (Psv) Ages Of Wilson Crk, Plc08-1, Bl04-4, Ol90-1 And 2, Larry V. Benson

United States Geological Survey: Datasets

In the paleomagnetic secular variation (PSV) ages folder:

The data for OL90-1 and 2 have not been published

The data for PLC08-1 are reported in:

Benson, L.V., Smoot, J.P., Lund, S.P., Mensing, S.A., Rye, R.O., 2013. Insights from a synthesis of old and new climate-proxy data from the western Lahontan Basin for the period 48 to 11.5 ka. Quaternary International310, 62-82.

Lund, S., Benson, L., Negrini, R., Liddicoat, J., Mensing, S., 2016. A full-vector paleomagnetic secular variation record (PSV) from Pyramid Lake (Nevada) from 47-17 ka: Evidence for the successive Mono Lake and Laschamp Excursions. Earth and Planetary Sciences …

Pyramid And Winnemucca Lake Basin Carbonate Data, Larry V. Benson

United States Geological Survey: Datasets

In the Pyramid and Winnemucca lake basin carbonate data folder:

New unpublished and previously published ¹⁴C and calibrated ages for materials in the Winnemucca Caves are reported in the table and in the references listed below the table

¹⁴C and calibrated ages for Winnemucca Lake Basin carbonates are reported in:

Benson, L.V., Hattori, E.M., Southon, J., Aleck, B., 2013. Dating North America’s oldest petroglyphs, Winnemucca Lake subbasin, Nevada. Journal of Archaeological Science 40, 4466-4476.

Tufa ⁸⁷Sr, ¹⁸O, and ¹³C data are reported in:

Benson, L.V., Smoot, J.P., Lund, S.P., Mensing, S.A., Rye, R.O., 2013. Insights …

Reconstructed Discharge For Truckee River, Larry V. Benson

United States Geological Survey: Datasets

Reconstructed Discharge for Truckee River

Name Date modified Time modified Size MB Extension

Reconstructed Discharge Truckee R\ Reconstructed Discharge for Truckee River.xlsx 11.11.2017 22:40:52 0.02 xlsx

Reconstructed discharge of the Truckee River was made considering losses to evaporation in all upstream reservoirs and corrected for diversion from the Derby Dam to the Newlands area. These data were never previously published.

General Comment: In most cases an age model based on ¹⁴C analyses is not included with the datasets although ones were created for the original publications. Given the general problems with ¹⁴C ages in the lakes of the …

Walker Lake Basin Data, Larry V. Benson, Steve P. Lund

United States Geological Survey: Datasets

Walker Lake Basin Data

Name Date modified Time modified Size MB Extension

Walker Lake Core 84-8 isotope and age data.xls 27.01.2018 15:25:52 0.03 xls

Walker Lake core WL002 PSV age and chemical data.xlsx 09.02.2018 20:04:50 0.03 xlsx

In the Walker Lake Basin folder:

Depth, ¹⁴C age (not corrected for reservoir effect), ¹⁸O, ¹³C data for core 84-8 are reported in:

Benson, L. V., 1988, Preliminary paleolimnologic data for the Walker Lake subbasin, California and Nevada: United States Geological Survey Water-Resources Investigations Report 87-4258, 50 p. Palaeogeography, Palaeoclimatology, Palaeoecology 240: 497-507.

Depth, PSV age, TIC , ¹⁸O, …

Pyramid Lake Core Data, Larry V. Benson

United States Geological Survey: Datasets

Pyramid Lake Core Data

14C and calibrated ages for core PLC08-1.xlsx 01.03.2014 19:45:30 0.01 xlsx

14C and calibrated ages for core PLC92B.xlsx 04.03.2014 16:41:30 0.01 xlsx

14C and calibrated ages for core PLC97-3.xlsx 01.03.2014 19:50:48 0.01 xlsx

CalKa Depth TOC TIC 18O 13C for PLC97-1.xlsx 09.11.2017 20:51:22 0.04 xlsx

Depth 14CAge Corrected 14C AGE CAL Age PLC98-4.xlsx 15.11.2017 18:26:12 0.01 xlsx

Depth 180 13C TOTC TOC TIC porosity CYBP Box Core PLB98-2.xlsx 01.03.2014 20:00:46 0.01 xlsx

Depth CalAge TIC TOTC TOC 13C 18O PLC98-4.xlsx 02.03.2014 00:32:20 0.05 xlsx

Depth Equivalent Depth in PLC08-1 PSV age 180 13C TIC TOC for …

Precipitation And Growth Of Barite Within Hydrothermal Vent Deposits From The Endeavour Segment, Juan De Fuca Ridge, John William Jamieson, Mark D. Hannington, Margaret K. Tivey, Thor Hansteen, Nicole M.-B. Williamson, Margaret Stewart, Jan Fietzke, David Butterfield, Matthias Frische, Leigh Allen, Brian Cousens, Julia Langer

United States Department of Commerce: Staff Publications

Hydrothermal vent deposits form on the seafloor as a result of cooling and mixing of hot hydrothermal fluids with cold seawater. Amongst the major sulfide and sulfate minerals that are preserved at vent sites, barite (BaSO₄) is unique because it requires the direct mixing of Ba-rich hydrothermal fluid with sulfate-rich seawater in order for precipitation to occur. Because of its extremely low solubility, barite crystals preserve geochemical fingerprints associated with conditions of formation. Here, we present data from petrographic and geochemical analyses of hydrothermal barite from the Endeavour Segment of the Juan de Fuca Ridge, northeast Pacific Ocean, …

Sea Lamprey Mating Pheromone Registered By U.S. Environmental Protection Agency As First Vertebrate Pheromone Biopesticide, Marc Gaden, Marisa Lubeck

United States Geological Survey: Publications

Ann Arbor, MI – The U.S. Environmental Protection Agency registered a sea lamprey mating pheromone, 3kPZS, as the first ever vertebrate pheromone biopesticide in late December, 2015. Like an alluring perfume, the mating pheromone is a scent released by male sea lampreys to lure females onto nesting sites. Research and development of the mating pheromone was funded by the Great Lakes Fishery Commission, with additional support from the Great Lakes Restoration Initiative, in collaboration with federal government, university, and private industry partners.

A Niobium Deposit Hosted By A Magnetite–Dolomite Carbonatite, Elk Creek Carbonatite Complex, Nebraska, Usa, Michael J. Blessington

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

The Elk Creek Carbonatite Complex (ECCC) is a large Early Cambrian carbonatite complex that intrudes Precambrian basement rocks in Southeast Nebraska. This dolomitic carbonatite complex includes a magnetite-dolomite rock with accessory barite, ilmenite, rutile, and quartz. This rock is identified by a characteristic enrichment in niobium due to accessory pyrochlore mineralization in the form of disseminations and inclusions in ilmenite and magnetite. Pyrochlore is also present in other carbonatite rocks in the complex as an accessory mineral with sporadic local high-grade intercepts in drill cores.

Carbonatite rock samples are characterized by transmitted-light microscopy, cathodoluminescent microscopy, backscattered electron imaging (BEI), and …

Origin And Distribution Of The Mississippian–Pennsylvanian Boundary Unconformity In Marine Carbonate Successions With A Case Study Of The Karst Development Atop The Madison Formation In The Bighorn Basin, Wyoming, Lucien Nana Yobo

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

The causal mechanism of the widespread unconformity that encompasses the Mississippian – Pennsylvanian boundary remains poorly understood. This unconformity, first thought to be restricted to North America, is now known to be present in other regions of the globe. Possible causes for the unconformity include (1) sea level draw down from the onset of glaciation at start of the late Paleozoic ice age and (2) increased tectonic activity from the formation of the supercontinent of Pangea. Thus the origin of the unconformity is still poorly constrained.

This study examines possible causal mechanisms for the widespread unconformity that encompasses the Mississippian …

The Evolution Of Respiratory O2/No Reductases: An Out-Of-The-Phylogenetic-Box Perspective, Anne-Lise Ducluzeau, Barbara Schoepp-Cothenet, Robert Van Lis, Frauke Baymann, Michael J. Russell, Wilfgang Nitschke

Department of Biochemistry: Faculty Publications

Complex life on our planet crucially depends on strong redox disequilibria afforded by the almost ubiquitous presence of highly oxidizing molecular oxygen. However, the history of O₂-levels in the atmosphere is complex and prior to the Great Oxidation Event some 2.3 billion years ago, the amount of O₂ in the biosphere is considered to have been extremely low as compared with present-day values. Therefore the evolutionary histories of life and of O₂-levels are likely intricately intertwined. The obvious biological proxy for inferring the impact of changing O₂-levels on life is the evolutionary history …

Pore Water Extraction For Unsaturated Zone Isotope Research: An Investigation Using An Immiscible Displacement Fluid And A Centrifuge, Caitlin Burnett Weaver

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

Accurate and reliable pore water extraction techniques are important to an array of scientific fields including, but not limited to, hydrogeology, soil science, and paleoenvironmental research. The aim of the current project is to test the applicability of an immiscible displacement extraction technique for stable isotopes of water under a range of textural, hydrologic, and chemical conditions. In this study, laboratory experiments were conducted to establish the extent to which the proposed method 1) achieves sufficient yield for laboratory isotopic analyses, 2) results in isotopic exchange between water and the displacement fluid, 3) conserves initial isotopic compositions of spike test …

Data-Driven Diagnostics Of Terrestrial Carbon Dynamics Over North America, Jingfeng Xiao, Scott V. Ollinger, Steve Frolking, George Hurtt, David Y. Hollinger, Kenneth J. Davis, Yude Pan, Xiaoyang Zhang, Feng Deng, Jiquan Chen, Dennis D. Baldocchi, Beverly E. Law, M. Altaf Arain, Ankur R. Desai, Andrew D. Richardson, Ge Sun, Brian Amiro, Hank Margolis, Lianhong Gu, Russell L. Scott, Peter D. Blanken, Andrew E. Suyker

School of Natural Resources: Faculty Publications

The exchange of carbon dioxide is a key measure of ecosystem metabolism and a critical intersection between the terrestrial biosphere and the Earth’s climate. Despite the general agreement that the terrestrial ecosystems in North America provide a sizeable carbon sink, the size and distribution of the sink remain uncertain. We use a data-driven approach to upscale eddy covariance flux observations from towers to the continental scale by integrating flux observations, meteorology, stand age,aboveground biomass, and a proxy for canopy nitrogen concentrations from AmeriFlux and Fluxnet-Canada Research Network as well as a variety of satellite data streams from the MODIS sensors. …

Interpreting The Paleozoogeography And Sea Level History Of Thermally Anomalous Marine Terrace Faunas: A Case Study From The Last Interglacial Complex Of San Clemente Island, California, Daniel R. Muhs, Lindsey T. Groves, R. Randall Schumann

United States Geological Survey: Publications

Marine invertebrate faunas with mixtures of extralimital southern and extralimital northern faunal elements, called thermally anomalous faunas, have been recognized for more than a century in the Quaternary marine terrace record of the Pacific Coast of North America. Although many mechanisms have been proposed to explain this phenomenon, no single explanation seems to be applicable to all localities where thermally anomalous faunas have been observed. Here, we describe one such thermally anomalous fossil fauna that was studied on the second emergent marine terrace at Eel Point on San Clemente Island. The Eel Point terrace complex is a composite feature, consisting …

Identifying Sources Of Aeolian Mineral Dust: Present And Past, Daniel R. Muhs, Joseph M. Prospero, Matthew C. Baddock, Thomas E. Gill

United States Geological Survey: Publications

Aeolian mineral dust is an important component of the Earth’s environmental systems, playing roles in the planetary radiation balance, as a source of fertilizer for biota in both terrestrial and marine realms and as an archive for understanding atmospheric circulation and paleoclimate in the geologic past. Crucial to understanding all of these roles of dust is the identification of dust sources. Here we review the methods used to identify dust sources active at present and in the past. Contemporary dust sources, produced by both glaciogenic and non-glaciogenic processes, can be readily identified by the use of Earth-orbiting satellites. These data …

Hydrochemical Investigation Of A Transient Parafluvial Zone Under Drought Conditions, Platte River, Nebraska, Audrey R. Boerner

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

Shallow groundwater (0.5 m -1.2 m deep) beneath a vegetated and non-vegetated fluvial island was observed in the lower Platte River, Nebraska, USA during exceptional summer drought. Over the course of three months, sub-hourly measurements of hydraulic head, and weekly measurements of redox indicators, δ²H, δ¹⁸O, and dissolved gases were analyzed together with nitrogen and carbon species from an array of shallow piezometers in the river bed and islands. These data were compared with the same parameters collected from a 15 m-deep riparian borehole. Vertical hydraulic gradients in the island piezometers indicated the vertical component to …

Oil-Source Rock Correlation In The Late Paleozoic, Denver Basin, Nebraska: The Search For A Negative Δ¹³C Anomaly In Pennsylvanian–Permian Cyclothems, John P. Still

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

Late Paleozoic sedimentation in the Denver basin occurred in two environmentally distinct depocenters. The northern-most Alliance Basin has been interpreted to have a restricted character: anhydrite-bearing mudstones are present in cyclothems comprising wackestone, packstone and mudstone. The source of petroleum produced from these intervals is considered to be organic-rich units within these cyclothems. Oil recovered from late Paleozoic reservoirs has δ13C values that range from -30.8‰ to -28.8‰: values that are lower than those reported previously for prospective source rocks from this interval. Cores from seven wells that penetrate upper Pennsylvanian to lower Permian rocks have been chosen for analysis. …

Paleoecology Of Nebraska’S Ungulates During The Eocene–Oligocene Climate Transition, Grant S. Boardman

Department of Earth and Atmospheric Sciences: Dissertations, Theses, and Student Research

The White River Group (WRG) preserves the Eocene-Oligocene climate transition (EOCT), an interval of global cooling and drying during the onset of Antarctic glaciation. In the Great Plains, a shift from forested conditions to drier woodland-savanna biomes is hypothesized to have occurred at this time. I test this hypothesis through the analyses of several paleoenvironmental proxies on the teeth of 12 WRG ungulate species: stable carbon and oxygen isotopes from tooth enamel, and mesowear and microwear texture. The EOCT shift toward more open habitats and lower vegetation density under drying climates should have resulted in an increase in mean carbon …

Assessment Of Coal Geology, Resources, And Reserve Base In The Powder River Basin, Wyoming And Montana, James A. Luppens, David C. Scott, Lee M. Osmonson, Jon E. Haacke, Paul E. Pierce

United States Geological Survey: Publications

Using a geology-based assessment methodology, the U.S. Geological Survey estimated in-place resources of 1.07 trillion short tons of coal in the Powder River Basin, Wyoming and Montana. Of that total, with a maximum stripping ratio of 10:1, recoverable coal was 162 billion tons. The estimate of economically recoverable resources was 25 billion tons.

Chemostratigraphy Of The Early Pliocene Diatomite Interval From Mis And-1b Core (Antarctica): Paleoenvironment Implications, Giovanna Scopelliti, Adriana Bellanca, Donata Monien, Gerhard Kuhn

ANDRILL Research and Publications

The AND-1B drill core (1285 m-long) was recovered, inside the ANDRILL (ANtarctic geological DRILLing) Program, during the austral summer of 2006/07 from beneath the floating McMurdo Ice Shelf. Drilling recovered a stratigraphic succession of alternating diamictites, diatomites and volcaniclastic sediments spanning about the last 14 Ma. A core portion between 350 and 480 mbsf, including a 80 m-thick diatomite interval recording the early Pliocene warming event, was investigated in term of opal biogenic content and element geochemistry. Across the diatomite interval, in spite of the lithological uniformity, a fluctuating biogenic opal profile mirrors the δ18O record, testifying a decrease in …

Effects Of Chiloquin Dam On Spawning Distribution And Larval Emigration Of Lost River, Shortnose, And Klamath Largescale Suckers In The Williamson And Sprague Rivers, Oregon, Barbara A. Martin, David A. Hewitt, Craig M. Ellsworth

United States Geological Survey: Publications

Chiloquin Dam was constructed in 1914 on the Sprague River near the town of Chiloquin, Oregon. The dam was identified as a barrier that potentially inhibited or prevented the upstream spawning migrations and other movements of endangered Lost River (Deltistes luxatus) and shortnose (Chasmistes brevirostris) suckers, as well as other fish species. In 2002, the Bureau of Reclamation led a working group that examined several alternatives to improve fish passage at Chiloquin Dam. Ultimately it was decided that dam removal was the best alternative and the dam was removed in the summer of 2008. The U.S. …

The Mineral Industry Of Nebraska

United States Geological Survey: Publications

In 2013, the value of the nonfuel mineral production1 in the State of Nebraska was $166 million,2 0.2% of the total U.S. nonfuel mineral production, ranking it 39th in the country. In 2012, the corresponding value was $160 million,2 0.2% of the Nation’s total nonfuel mineral production, ranking it 36th among the 50 States. In 2013, on a per capita basis, nonfuel mineral production in Nebraska in 2013 had a value of $89 compared with the national average of $238. In 2012, the per capita value was $86 compared with the national average of $241. The value of nonfuel mineral …

Reservoir Potential Of Sands Formed In Glaciomarine Environments: An Analog Study Based On Cenozoic Examples From Mcmurdo Sound, Antarctica, Christopher R. Fielding, Brian A. Blackstone, Tracy D. Frank, Zi Gui

Department of Earth and Atmospheric Sciences: Faculty Publications

This paper provides documentation of unexpectedly high-reservoir-quality glaciomarine sands found in the Cenozoic succession beneath McMurdo Sound, Antarctica, as an analogue study for evaluations of hydrocarbon prospectivity in basins elsewhere. The Oligocene to Lower Miocene succession of the Victoria Land Basin, an extant portion of the West Antarctic Rift System, comprises diamictites, mudrocks, and sandstones with minor conglomerates. These lithologies are arranged in repetitive stacking patterns (cycles), interpreted to record repeated advance and retreat of glaciers into and out of the basin, with attendant eustatic and isostatic effects. Phases of ice retreat within the cycles comprise an array of mudrocks, …

Evolution With Depth From Detrital To Authigenic Smectites In Sediments From And-2a Drill Core (Mcmurdo Sound, Antarctica), Francesco Iacoviello, Giovanna Giorgetti, Fernando Nieto, Isabella Turbanti Memmi

ANDRILL Research and Publications

We have examined the nature and origin of smectites in glaciomarine sediments of the AND-2A drill core (McMurdo Sound, Antarctica) by means of X-ray diffraction (XRD) analyses on the clay fraction, field emission scanning electron microscopy (FESEM), scanning electron microscopy (SEM) observations and SEM-EDS microanalyses on smectite particles. Relying on the smectite variation throughout the drill core it was possible to split the sequence into three units. Smectites throughout the core are either detrital or authigenic. Detrital smectites are close to montmorillonite-beidellite in composition while newly-formed smectites frequently have higher Fe-Mg contents and intermediate compositions between the saponite and nontronite …