Permian Paleoclimate Data from Fluid Inclusions in Halite

Chemical Geology 154Ž. 1999 113±132

Permian paleoclimate data from fluid inclusions in halite

Kathleen Counter Benison a,b,), Robert H. Goldstein a a The Department of Geology, The UniÕersity of Kansas, Lawrence, USA b The Kansas Geological SurÕey, Lawrence, KS, USA

Abstract

This study has yielded surface water paleotemperatures from primary fluid inclusions in mid Permian Nippewalla Group halite from western Kansas. A `cooling nucleation' method is used to generate vapor bubbles in originally all-liquid primary inclusions. Then, surface water paleotemperatures are obtained by measuring temperatures of homogenization to liquid. Homogenization temperatures ranged from 218Cto508C and are consistent along individual fluid inclusion assemblages, indicating that the fluid inclusions have not been altered by thermal reequilibration. Homogenization temperatures show a range of up to 268C from base to top of individual cloudy chevron growth bands. Petrographic and fluid inclusion evidence indicate that no significant pressure correction is needed for the homogenization temperature data. We interpret these homogenization temperatures to represent shallow surface water paleotemperatures. The range in temperatures from base to top of single chevron bands may reflect daily temperatures variations. These Permian surface water temperatures fall within the same range as some modern evaporative surface waters, suggesting that this Permian environment may have been relatively similar to its modern counterparts. Shallow surface water temperatures in evaporative settings correspond closely to local air temperatures. Therefore, the Permian surface water temperatures determined in this study may be considered proxies for local Permian air temperatures. q 1999 Elsevier Science B.V. All rights reserved.

Keywords: Lacustrine sediments; Evaporites; Nonmarine; Nippewalla group; Homogenization temperatures

1. Introduction Evaporite deposits appear to be a treasure chest of paleoclimate data. The formation of salt minerals at Burgeoning interest in paleoclimatology has re- the earth's surface is extremely sensitive to local sulted from new data on changes in the earth's climatic conditions. Primary fluid inclusions pre- atmosphere and a desire for predictions of future served in depositional evaporite minerals may be climate change. How better to understand natural remnants of ancient hydrosphere and atmosphere. fluctuations in climate than to obtain a record of Fluid inclusion studies can yield detailed information climate data from the past? This study uses fluid about the water temperatures, water chemistries, and inclusion data from Permian halite to construct a even atmospheric conditions under which evaporites record of ancient earth surface temperature. formed. Geologists have maintained a healthy skepticism toward fluid inclusion data from evaporites, espe- ) Ž Corresponding author. Department of Geology, Central cially halite Roedder and Skinner, 1968; Wilcox, Michigan University, Mt. Pleasant, MI 48859, USA. E-mail: 1968; Kovalevich, 1975, 1976; Petrichenko, 1979; [email protected] Roedder and Belkin, 1980; Roedder, 1984b; Gold-

0009-2541r99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved. PII: S0009-2541Ž. 98 00127-2 114 K.C. Benison, R.H. GoldsteinrChemical Geology 154() 1999 113±132 stein and Reynolds, 1994. . Halite's high solubility geothermal gradientsŽ Petrichenko, 1979; Roedder and potential for deformation have raised doubts and Belkin, 1980; Roedder, 1984b. . When deforma- about the preservation of its fluid inclusions. Expo- tion of halite occurs, only the outer portions of halite sure to even moderate heat may alter fluid inclusions crystals seem to be affected, whereas the centers of in halite. However, possible fluid inclusion alteration crystals remain unaltered. This results in halite crys- can be carefully evaluated by petrography and mi- tals with altered, clear, outer rims and unaltered, crothermometric tests. If these tests show that pri- cloudy, primary inclusion-rich coresŽ Petrichenko, mary fluid inclusions have not been altered since 1979; Roedder, 1984a,b. . Thus, fluid inclusions in entrapment, these fluid inclusions may be considered ancient halites may be considered representative of representative of evaporative parent waters. original conditions if alteration can be evaluated and This paper demonstrates how Permian surface dismissed. water temperatures have been determined from halite Fluid inclusions in halite have been successfully in the Nippewalla Group of western Kansas. Petrog- used to reconstruct detailed surface water tempera- raphy was used to document that this halite precipi- tures. Observation of solid-to-liquid homogenization tated in shallow waters. An underused `cooling nu- upon heating of inclusions containing liquid and a cleation' method was employed to measure tempera- daughter crystal has yielded minimum surface water tures at which fluid inclusions were trapped. These paleotemperatures. Experimental solid±liquid ho- resultant surface water paleotemperatures represent mogenization runs have been conducted on inclu- significant paleoclimatic data that can be used to sions in halite containing sylvite, carnallite, ep- refine paleoclimate models. somite, and bischofite daughter crystalsŽ Petrichenko, 1979.Ž. . Lowenstein and Spencer 1990 used solid± 1.1. PreÕious studies of fluid inclusions in halite liquid homogenization temperatures of sylvite daughter crystals in halite from the Devonian Prairie For- The validity of fluid inclusion data from halite has mation to estimate Devonian water temperature. been a debatable subject. Some characteristics of Another approach has been used to determine halite, in particular its high solubility and potential surface water paleotemperatures from ancient halites for deformation, have led geologists to hold a healthy whose fluid inclusions lack daughter crystals. All- skepticism about preservation of its fluid inclusions. liquid primary inclusions at room temperature indi- In halite, fluid inclusions are more vulnerable to cate mineral growth below approximately 508C stretching, leaking, and necking down than in most ŽKovalevich, 1975; Petrichenko, 1979; Goldstein and other minerals. These problems, coupled with the Reynolds, 1994. . Vapor bubbles can be nucleated proposal of salt as repository sites for radioactive artificially in some all-liquid inclusions so that ho- waste, has generated valuable research on the valid- mogenization temperatures below 508C can be mea- ity of fluid inclusion data in halite. sured. PetrichenkoŽ. 1979 nucleated vapor bubbles in Possible alteration of fluid inclusions in halite fluid inclusions in natural halite by cooling to y308 includes thermal reequilibration, migration, and de- to y158C. Resultant homogenization temperatures formation. Roedder and SkinnerŽ. 1968 warned that were all below 608C and were reproducible to within leakage from thermal reequilibration may be a prob- 1±28C. lem. Experimental work showed that some fluid This cooling nucleation method of measuring ho- inclusions in ancient halite have indeed been altered, mogenization temperatures in originally all-liquid but some have not and these may yield valid fluid primary fluid inclusions was successfully used in inclusion data. Experimental work argues against both modern and Pleistocene ephemeral lakersalt much leakage and stretching of fluid inclusions in pan halite from Death Valley, CAŽ Brown, 1995; haliteŽ. Wilcox, 1968; Petrichenko, 1979 . When in- Roberts and Spencer, 1995. . In order to test this ternally overpressured from overheating, only the method, those workers collected newly grown halite largest inclusions tend to stretch. Likewise, only the and measured temperatures of the shallow water largest inclusions tend to migrate, but only when from which the halite precipitated. Primary fluid subjected to huge, geologically unreasonable inclusions in this modern Death Valley halite were K.C. Benison, R.H. GoldsteinrChemical Geology 154() 1999 113±132 115

Fig. 1. Histogram of homogenization temperatures measured by the `cooling nucleation' method in initially all-liquid primary fluid inclusions from modern Death Valley halite. Plotted above are the temperature of the water which these halite crystals grew. After Roberts and SpencerŽ. 1995 . then cooled in order to nucleate vapor bubbles for homogenization temperature measurements. The homogenization temperatures fell within the same temperature range as the water in which the halite grew Fig. 2. Stratigraphic position of the Permian Nippewalla Group in Ž.Fig. 1 . This indicates that homogenization tempera- Kansas and northern Oklahoma. After BaarsŽ. 1990 and Rascoe Ž. tures obtained with the cooling nucleation method and Baars 1972 . accurately reflect temperatures of evaporative parent waters. siliciclastic siltstones and sandstones, bedded anhy- Although it has been shown that the cooling drite, bedded halite, and minor grey siliciclastic lam- nucleation method can be used to obtain accurate inated mudstones. HoldowayŽ. 1978 claimed that the surface water temperatures from all-liquid fluid in- low bromide content of the halite and its association clusions in recent shallow water halite, does this with red beds indicate that Nippewalla Group deposi- method work for ancient halites? A preliminary ver- tion took place in a shallow, continental basin. sion of this study yielded encouraging data that this This study uses two cores of the Nippewalla method is applicable to ancient halitesŽ Benison, Group from western KansasŽ. Fig. 3 . The present 1995. . burial depth of the halite samples used for this study is between 1365 and 1627 ftŽ. 416.2 and 496.2 m .

2. Geologic setting

Permian red bed-hosted evaporites have a wide regional extent in North America, occupying much of the surface and subsurface of the midcontinent regionŽ. Walker, 1967 . In Kansas and Oklahoma, these rocks are known as the Nippewalla GroupŽ Fig. 2.Ž. and have been described by Norton 1938 , SwinefordŽ. 1955 , Scott and Ham Ž. 1957 , Ham Ž.1960 , Fay Ž 1964, 1965 . , Fay et al. Ž. 1965 , and HoldowayŽ. 1978 . These studies concentrated mostly on field and core descriptions. The Nippewalla Group Fig. 3. Map of Kansas showing locations of two cores used in this of the mid Permian consists mostly of red bed study. 116 K.C. Benison, R.H. GoldsteinrChemical Geology 154() 1999 113±132

There is no evidence of previous deep burial but Kansas and the Atomic Energy Commission No. 5 there may have been up to 600 ftŽ. 183 m of rock core from Wichita, KS, were used for this fluid removed from the overlying section by erosionŽ Mer- inclusion study. Both of these cores were drilled riam, 1963. . There have been a number of igneous during the 1960's using drilling mud prepared with intrusions described in the midcontinentŽ Brookins halite-saturated brines to prevent dissolution of the and Naeser, 1971. , but none are known within ap- bedded halite. They have since been stored in sealed proximately 375 km of the study sites. Therefore, plastic to discourage attack by atmospheric moisture. there is no geologic evidence for significant thermal Halite samples were prepared with careful atten- alteration of the halite. tion paid to avoidance of water and heat. Halite was slabbed and cut to thick section size on a trim saw using Tufflo 100 water-free cutting oil. Oil was 3. Experimental methods cleaned from halite with isopropol alcohol. Halite Halite from nine stratigraphic levels in two cores, samples were then ground and polished manually on the Anadarko Davis No. 1 core from Seward County, dry sandpapers of 60, 100, 220, 320, 400, 600, and

Fig. 4. Schematic representation of idealized closed basin cycle and saline pan cycle in the Nippewalla Group. The idealized closed basin cycle ranges from approximately 1 m to 20 m in thickness. It is composed of grey siliciclastics, bedded anhydrite, bedded halite, and red bed siliciclastics deposited in perennial lakes, ephemeral lakes and saline pans, saline mudflats, dry mudflats, aeolian sand flats and sand dunes. The saline pan cycle, ranging from 6 to 17 cm in thickness, is composed mostly of halite with some anhydrite inclusions and red mud. The saline pan halite precipitated in a shallow lake that underwent periods of flooding, evaporite concentration, and desiccation. K.C. Benison, R.H. GoldsteinrChemical Geology 154() 1999 113±132 117

the inclusions. Freezing would cause the inclusions to stretch, thus yielding inaccurate homogenization temperatures. We know from freezingrmelting runs in other Nippewalla Group halite samples that these inclusions require supercooling to at least y1008C to freeze. Further, after cooling at approximately y108C in the freezer, these inclusions have maintained their original size and shape. Halite samples were contained in capped glass vials with several

pellets of CaCl2 desiccant in order to prevent con- densation of water vapor on the halite during cooling. Samples were kept in the freezer for approximately one week.

Fig. 5. Photomicrograph of upward-oriented chevron halite crystal truncated by dissolution pipe filled with clear halite cement. Boxed arrow indicates stratigraphic up.

1500 grit, and 1 mm and 0.3 mm diamond paper. Polished slabs were glued to large format glass thin section slides, and ground and polished manually on sandpaper to thick section thicknessŽ. 1±2 mm . To test that thick section preparation did not alter fluid inclusion data, uncut, unpolished halite cleavage chips were also used. These halite chips were prepared simply by cleaving to 1±2 mm thick fragments with a razor blade. Detailed fluid inclusion petrography, including sketching and photography of halite samples, was performed in order to document all-liquid primary fluid inclusions before thick sections were broken to pieces small enough to fit into the sample chamber of the fluid inclusion stage. Halite samples were placed in a standard kitchen Fig. 6. Photomicrograph showing primary fluid inclusion banding y y in chevron halite. Note cloudy, inclusion-rich growth bands and freezer at temperatures between 128C and 108C. clear, inclusion-poor growth bands. Boxed arrow indicates strati- These temperatures were not low enough to freeze graphic up. 118 K.C. Benison, R.H. GoldsteinrChemical Geology 154() 1999 113±132

of the inclusionŽ see Roedder, 1984a, Figs. 4±10, p. 103. . All-liquid inclusions remained in each fluid inclusion assemblage. Inclusion size did not influence vapor bubble nucleation. Along individual fluid inclusion assemblages, both small and large inclusions remained without vapor bubbles. Likewise, the inclusions that yielded vapor bubbles represented the entire range of inclusion sizes. The remaining all- liquid inclusions probably formed at the same temperatures as those that nucleated vapor bubbles. Fail- ure of vapor bubble formation in these all-liquid inclusions may simply be a problem of nucleation kinetics. As samples were removed from the freezer, they were rushed to a Fluid, Inc. U.S.G.S.-modified gas- flow heatingrfreezing stage that had been precooled to y108C. Samples were held at between y108C Fig. 7. Photomicrograph of primary fluid inclusion banding in and 08C until the nucleated vapor bubbles were cumulate halite. Boxed arrow indicates stratigraphic up. located and then warmed slowly. The rate of warm- ing was approximately 0.58Crmin at the lower tem- peraturesŽ. up to about 158C and then slowed to After cooling, the majority of fluid inclusions had 0.1±0.28Crmin at warmer temperatures. Homoge- not nucleated vapor bubbles. Only 10±20% of inclu- nization of vapor bubbles to liquid was observed and sions had vapor bubbles after cooling. Nucleated recorded. Cycling was attempted on all homogeniza- vapor bubbles appeared as mere pinpoints and are tion runs in order to observe the most accurate estimated to occupy less than 1% of the total volume homogenization temperatureŽ Goldstein and Reynolds, 1994, p. 93±95. . After true homogenization was reached, cooling on the stage would not cause renucleation of the vapor bubble. Homogeniza-

Fig. 8. Photomicrograph of several `high frequency' growth bands Fig. 9. Photomicrograph of primary inclusions along chevron Ž.defined here as fluid inclusion assemblages within one single growth bands truncated by a curved plane of large, irregular-shaped cloudy chevron band. Boxed arrow indicates stratigraphic up. secondary inclusions. Boxed arrow indicates stratigraphic up. K.C. Benison, R.H. GoldsteinrChemical Geology 154() 1999 113±132 119

tains both pseudomorphs after bottom-growth swal- lowtail gypsum and rounded sand-sized clasts of anhydrite associated with desiccation cracks and small-scale wave ripples. The bedded halite has characteristics of shallow ephemeral saline lake and salt pan featuresŽ Lowenstein and Hardie, 1985; also, Wardlaw and Schwerdtner, 1966; Hardie et al., 1978, 1985; Handford, 1982, 1990; Hardie et al., 1985; Casas, 1987; Lowenstein, 1988; Roberts et al., 1994. . Cm-scale bottom-growthŽ. upward orientation chevron halite crystalsŽ. Fig. 5 , mm-scale cumulate Fig. 10. Histogram of homogenization temperatures plotted against `hopper' halite crystals, and solid anhydrite inclu- number of inclusions. This histogram represents homogenization sions precipitated in shallow saline water. Dissolu- measurements from 234 primary fluid inclusions from nine strati- tion surfaces, vertical dissolution pipesŽ. Fig. 5 , and graphic levels in two cores of Nippewalla Group halite. mud partings in the halite mark periods of flooding and desiccation cracks and efflorescent salt crusts suggest periods of desiccation. Red siliciclastic siltstones dominated by displacive halite and anhydrite tion runs were repeated after recooling in the freezer were most likely deposited as saline mudflats. Red and homogenization temperatures for approximately siliciclastic siltstones with abundant desiccation 50% of the inclusions were reproduced to within cracks and root traces and minor Microcodium cal- 18C. cretes were deposited in a dry mudflat environment. A second method of nucleating vapor bubbles was Hematite-coated and halite-cemented quartz sand- attempted by cooling fluid inclusions to y15 to stones display planar reverse-graded bedding, high y108C in the fluid inclusion stage instead of the angle, large-scale cross-strata, and well-sorted, very freezer. Very few fluid inclusions nucleated vapor well-rounded, bimodal grains. These sandstones are bubbles in the fluid inclusion stage. This may sug- interpreted as eolian sand flat and sand dune de- gest that time of cooling is an important factor in the posits. These observation indicate that the large scale nucleation of vapor bubbles in originally all-liquid cycles are best interpreted as general `shallowing-up- inclusions. ward', desiccation trends in a closed basin that may represent changes from wetter to drier climates. The `mini-cycles' formed by flooding, evaporative con- 4. Environment of deposition centration, and desiccation events in the saline pan setting of the closed basin. The halite is located within large-scale cycles There is strong evidence that the bedded halite Ž.Fig. 4 consisting from base to top, of grey silici- precipitated in cm-scale, shallow water. The combi- clastic mudstone, bedded anhydrite, bedded halite, nation of chevron and cumulate crystals, along with red siliciclastic mudstone and siltstone with abundant dissolution and desiccation features within the same displacive halite, red siliciclastic mudstone and silt- bed of halite indicate formation in a saline pan stone with no displacive halite, and red sandstone. setting. The ephemeral lakes in modern saline pan On a smaller-scale, but found within the larger cy- settings are rarely more than a few tens of centime- cles, are mini-cycles of, from base to top, bedded ters and are typically only several centimeters in halite and red mudstone and siltstone. Grey siliciclas- depthŽ. Lowenstein and Hardie, 1985 . These shallow tic mudstones contain alternating organic-rich and water interpretations for the Nippewalla Group halite organic-poor planar laminae, abundant ostracodes and are important for two reasons:Ž. 1 they eliminate the plant material, and convoluted beds, suggesting la- need for a pressure correction on fluid inclusion custrine deposition. Bedded anhydrite was probably data; andŽ. 2 shallow waters typically are more deposited in shallow ephemeral saline lakes; it con- reflective of climate than are deep waters. 120 K.C. Benison, R.H. GoldsteinrChemical Geology 154() 1999 113±132

5. Fluid inclusion petrography sions are one-phase aqueous liquid inclusions at room temperatureŽ. Figs. 6±8 . Some primary inclu- Primary fluid inclusions are abundant and well- sions are two-phase, liquid and solid inclusions. The preserved in the Nippewalla Group halite. Chevron solids are most commonly anhydrite needles, but two and cumulate crystals are composed of alternating other unidentified minerals have also been observed. inclusion-rich and inclusion-poor growth bandsŽ Figs. These crystals are interpreted as `accidental' crystals 6 and 7, respectively. . Within each mm-thick inclu- trapped during halite crystal growth as opposed to sion-rich band are many thin `high frequency' fluid daughter crystals because they occur in minor quanti- inclusion bandsŽ. Fig. 8 . A typical cloudy, ties, do not have consistent solid±liquid volume inclusion-rich chevron band contains between 5 and ratios, and do not decrease in size upon heating as 15 of these high frequency bands. For this study, true daughter crystals would. Also, there are abun- each of these high frequency bands is considered an dant solid anhydrite inclusions in this halite, further individual fluid inclusion assemblageŽ Goldstein and evidence that anhydrite was precipitating at the same Reynolds, 1994. , meaning that petrography suggest time as the halite. Rare two-phase liquid±vapor pri- that all fluid inclusions along it formed at about the mary inclusions exist in cumulates and, less com- same time. monly, in chevrons. These tend to be larger inclu- Primary fluid inclusions have a cubic, negative sions with vapor-to-liquid ratios of at least 50% and crystal-shape. They range in size from 1 mmto are associated with abundant all-liquid inclusions several hundred mm in diameter, but most are be- and minor two-phase liquid±solid inclusions in the tween 5 and 30 mm. The majority of primary inclu- same fluid inclusion assemblages. Preliminary crush-

Fig. 11. Ranges of fluid inclusion homogenization temperatures plotted next to location of samples in the two cores. K.C. Benison, R.H. GoldsteinrChemical Geology 154() 1999 113±132 121

originated by subaqueous outgassing or, more likely, may contain Permian air which was trapped as halite crystals grew at the water±atmosphere interface. Secondary fluid inclusions in Nippewalla Group halite are easily distinguishable from primary inclu- sionsŽ. Fig. 9 . Secondary inclusions are irregular- shaped one-phase inclusions along curved healed microfractures that cross-cut halite crystal boundaries as well as chevron and cornet growth bands. LargerŽ. greater than 40±50 mm , cubic or irregular- shaped inclusions that are isolated in otherwise clear halite are ambiguous in origin, but may be either primary inclusions or inclusions trapped during re- Fig. 12. Histogram of homogenization temperatures plotted against crystallization of some halite. number of inclusions. This histogram represents primary fluid inclusion homogenization measurements from one stratigraphic X level, 1365 depth of Anadarko Davis No. 1 core, of Nippewalla Group halite. Each pattern represents data from an individual fluid 6. Homogenization data inclusion assemblage. Note that homogenization temperatures are fairly consistent within individual fluid inclusion assemblages. 6.1. Homogenization temperatures in Nippewalla Group halite ing runs performed on the vapor-rich primary inclusions show no change in size of vapor bubbles from Homogenization temperatures measured in 234 before to after crushing. These gas bubbles may have originally all-liquid primary fluid inclusions in Nipewalla Group halite range from 21.48C to 49.88C

Fig. 13. Histogram of homogenization temperatures plotted against size of inclusions. This histogram represents primary fluid inclu- Fig. 14. Schematic representation of chevron bands in a halite X sion homogenization measurements from one stratigraphic level, crystal from Anadarko Davis No. 1 core, 1406 depth. Note X 1365 depth of Anadarko Davis No. 1 core, of Nippewalla Group homogenization temperatures in relation to bands. Although ho- halite. Each symbol represents an individual assemblage. Note mogenization temperatures are consistent within individual fluid that homogenization temperatures within individual fluid inclusion inclusion assemblagesŽ. thin, high frequency growth bands , they assemblages are not dependent upon inclusion size. decrease from base to top of chevrons. 122 K.C. Benison, R.H. GoldsteinrChemical Geology 154() 1999 113±132

Ž.Fig. 10 . Among the nine individual stratigraphic temperature ranges. This is not surprising because levels in which halite was sampled, homogenization petrographic analysis shows that halite precipitated temperatures range slightlyŽ. Fig. 11 . For instance, in very shallowŽ. cm-scale water. In this environ- X homogenization temperatures measured from 1627 ment, water temperatures would be approximately in the Atomic Energy Commission core have the the same at both the bottom and top of the water most narrow rangeŽ. 328Cto468C , whereas halite column. X Y from the 1627 6 depth in the same core has the Within individual fluid inclusion assemblages, ho- widest rangeŽ. 218Cto478C. mogenization temperatures from both larger and Both bottom-growth chevron crystals and cumu- smaller inclusions fall within the same narrow range late hopper crystals yielded similar homogenization of no more than 88CŽ and many have agreement

Fig. 15. Graphic representation of homogenization temperature trends within and among cloudy, inclusion-rich and clear, inclusion-poor growth bands in five chevron halite crystals from the Nippewalla Group. Black circles mark average homogenization temperatures and bracketed lines show ranges for individual fluid inclusion assemblages within thicker chevron growth bands. Lines connecting black circles are extrapolated temperature trends. Upward decrease in homogenization temperatures from base to top of individual cloudy chevron bands may reflect daily fluctuations in surface water temperatures. K.C. Benison, R.H. GoldsteinrChemical Geology 154() 1999 113±132 123 within 28C; Fig. 12. . Measured temperatures are tures. But the few measurements made in these clear reported from inclusions ranging in size from 3 to chevron bands show temperatures that are intermedi- 380 mm. There is no correlation between size of ate between the lowsŽ at top of the next lower cloudy inclusions and homogenization temperatureŽ. Fig. 13 . band.Ž and the highs at the base of the next higher cloudy band; Figs. 14 and 15. . 6.2. Temperature trends

Although homogenization temperatures agree closely along individual fluid inclusion assemblages, 7. Discussion successive fluid inclusion assemblages within individual chevron growth bands show temperature trends. There are multiple fluid inclusion assem- 7.1. Validity of homogenization temperature data blages within each thickŽ. 100's of mm to mm-scale cloudy, inclusion-rich chevron band in bottom- Homogenization temperatures of primary fluid in- growth haliteŽ. Fig. 14 . Within each cloudy chevron clusions in halite, especially ancient halite, cannot be band, homogenization temperatures are highest in the considered representative of evaporative parent water fluid inclusion assemblage at the base of that cloudy temperatures until alteration of the fluid inclusions chevron. Each successively later fluid inclusion as- can be dismissed. semblage yields slightly lower homogenization tem- We have ruled out alteration of fluid inclusions by peratures, with the topmost assemblage having the thick section preparation. Uncut, unpolished halite lowest homogenization temperatures in the cloudy cleavage chips yielded the same range of homoge- chevron bandŽ. Figs. 14 and 15 . nization temperatures as did thick section fragments. We have only limited data on these temperature This suggests that thick section preparation had no trends on a chevron band-to-chevron band scale due effect on the fluid inclusions. to the small percentage of nucleated vapor bubbles Alteration of fluid inclusions by thermal reequili- after cooling and the difficulty of renucleating bub- bration also has been ruled out. Consistency of ho- bles after homogenization. Samples from different mogenization temperatures in fluid inclusion assem- stratigraphic levels in both cores show decreases in blages can be used to evaluate the possibility of homogenization temperature of approximately 68Cto thermal reequilibration. Goldstein and Reynolds 128C from base to top of cloudy chevron bandsŽ Fig. Ž.1994 suggested that if inclusions measured in a X 15.Ž . One cloudy chevron band at 1406Ž. 428.7 m fluid inclusion assemblage are of variable sizes or depth in Anadarko core. has homogenization temper- shapes, and if 90% of the homogenization tempera- atures of high 40's Ž.8C at its base to low 20's Ž.8Cat ture data from it fall within a 10±158C interval, then its top, reflecting a temperature decrease of approxi- the inclusions probably have not been altered by mately 268CŽ. Figs. 14 and 15 . It is succeeded by a thermal reequilbration. The homogenization tempera- cloudy chevron band with a trend from high 40's to ture data from the Nippewalla Group halite meet low 30's Ž.8C; Figs. 14 and 15 . In a crystal from these criteria. Each fluid inclusion assemblage has XY Anadarko core 1396 6Ž. 425.8 m with three succes- ranges of homogenization temperatures that fall sive cloudyrclear chevron couplets over a vertical within 88C. However, the great majority of fluid thickness of approximately 9 mm, the basal cloudy inclusion assemblagesŽ. 88% have homogenization chevron band has homogenization temperatures de- temperatures that fall into an even smaller interval of creasing upward from high 20's to low 20's in 8C. less than 58C and many have agreement within 28C The second cloudy chevron band and third, or top- Ž.Fig. 12 . This indicates that the fluid inclusions most, cloudy chevron band both have homogeniza- have not undergone thermal reequilibration. tion temperatures decreasing upward from low 40's Evaluating the relationship between inclusion size to low 30's Ž.8C. and homogenization temperatures is another impor- The clear chevron bands have very few inclusions tant test for determining if fluid inclusions have been from which to measure homogenization tempera- altered by thermal reequilbration. Experimental work 124 K.C. Benison, R.H. GoldsteinrChemical Geology 154() 1999 113±132 shows that the larger inclusions in halite tend to 7.2. Comparison with modern eÕaporatiÕe settings stretchmuchmorethansmallerinclusions ŽPetrichenko, 1979; Roedder and Belkin, 1980; The homogenization temperature data indicate that Roedder, 1984b. . Fluid inclusions that have stretched shallow surface waters that precipitated the Nippe- yield homogenization temperatures higher than the walla Group halite during the mid Permian had true entrapment temperature. Therefore, if these pri- temperatures of 218Cto508C. These are reasonable mary inclusions in the Nippewalla Group halite had temperatures for Permian surface waters since they stretched, the larger inclusions would tend to have fall within the same range as temperatures of some higher homogenization temperatures than the smaller modern playasŽ. continental ephemeral saline lakes inclusions. There is no relationship between size of and salinasŽ. marginal marine ephemeral saline lakes . inclusion and homogenization temperatureŽ. Fig. 13 . Because water chemistry and climatic conditions Thus, primary fluid inclusions in Nippewalla Group are important in the study of chemical sediments, halite have not been altered by thermal reequilibra- water temperatures have commonly been measured tion. in studies of modern evaporite environments. Re- The observations argue strongly against thermal ported temperatures for modern surface brines range reequilbration of the fluid inclusions. Thus, the ho- from approximately 08Cto858CŽ. Table 1 . For mogenization temperature data presented here are example, Casas et al.Ž. 1992 reported temperatures valid. of 128Cto388C for 1 cm deep water on a salt pan Moreover, petrographic and fluid inclusion evi- bordering Lake Dabusan in the Quidam Basin of dence indicate that no significant pressure correction China. Surface water temperatures range from 58Cto is needed for the homogenization temperature data. 708C at Salina Omotepec, Baja CAŽ Casas and The sedimentologic and petrographic observations Lowenstein, 1989. . argue that this halite formed in very shallowŽ cm- Temperature data for modern surface brines is not scale. surface waters. The crushing runs indicate complete. Year-round temperature data are not al- pressures near one atmosphere. Both pieces of evi- ways available due to desiccation of some of these dence indicate entrapment at low pressure so the saline lakes and harsh field conditions during ex- homogenization temperatures are essentially equal to tremely hot, arid summer months. However, enough entrapment temperatures. Therefore, the raw homog- temperature data have been collected to record sea- enization temperatures are approximately equal to sonal trends in some of these modern brines. For temperatures of surface waters from which the halite instance, BrownŽ. 1995 measured water temperatures precipitated. of 98Cto368C from November to May of 1993 at

Table 1 Surface water temperature in modern evaporative environments Locality Water temperature Water depth Reference Quidam Basin, China 12±388C 1 cm Casas et al., 1992 Salina Omotepec, Baja CA 5±708C surface Casas and Lowenstein, 1989 Lake Magadi, Kenya 15±858CŽ. hot springs present surface Eugster, 1970 Death Valley, CA 9±368CŽ. Nov.±May surface Brown, 1995 20±388CŽ. April±May surface Roberts and Spencer, 1995 43±508CŽ. Aug. Walker Lake, NV 2±328C shoreline Newton and Grossman, 1988 Salton Sea, CA 10±368C surface Carpelan, 1958 Great Salt Lake, UT y1±288C surface Eubank and Brough, 1980 Great Inagua salt works, Bahamas 24±358CŽ. Jan. surface Zimmermann, pers. comm. 28±368CŽ. Aug. Dead SeaŽ. south basin 35±408C Ž. summer surface Gornitz and Schreiber, 1981 19±238CŽ. winter K.C. Benison, R.H. GoldsteinrChemical Geology 154() 1999 113±132 125

Death Valley. Roberts and SpencerŽ. 1995 reported is probable that for most chevrons, growth is slower Death Valley water temperatures of 208Cto388C for and just one cloudy±clear couplet forms in the course April and May and 438Cto508C for August of the of one day. same year. Temperature data from a solar salt works The ephemeral lakersaline pan halite from the in the Bahamas exhibit less of a seasonal trend than Nippewalla Group grew in shallow surface brines at Death Valley, being approximately 108 in latitude temperatures of 218Cto508C. These Permian surface closer to the Equator and having a more humid water temperatures fall within the same range as climate. Surface brine temperatures at a solar salt some modern surface brines. Trends of decreasing work on Great Inagua Island in the Bahamas mea- temperatures observed from base to top of individual sured 248Cto358C in January and 288Cto368Cin chevron bands may reflect daily water temperature AugustŽ. H. Zimmermann, pers. comm. . variations. Modern surface water temperatures also fluctuate over the course of a day. Just before sunrise, temper- 7.3. Paleoclimatic significance atures are lowest and highest daily water temperatures occur in early afternoon. Measured tempera- Surface water paleotemperatures can be an impor- tures reflect diurnal changes of 108Cto128C at both tant aspect of paleoclimate studies. Modern surface Death Valley and Great Inagua IslandŽ Brown, 1995, water temperatures in ephemeral lakersaline pan Roberts and Spencer, 1995, H. Zimmermann, pers. settings are rather similar to surface air temperatures. comm.. . At Dabusun Lake, Quidam Basin, China, Therefore, surface water temperatures determined Casas et al.Ž. 1992 reported surface water Ž 1 cm from ancient evaporites can be used as estimates of depth. temperatures of 128C at 7:27 am, 228Cat ancient localized air temperatures. 11:20 am, and 388C at 5:25 pm during one August Surface water temperatures and air temperatures day. BrownŽ. 1995 pointed out that because workers reflect local climate factors such as latitude and usually sample temperatures between 9 am and 4 elevation. For example, Death Valley is situated at a pm, nighttime temperatures have not often been re- lower elevation than Great Salt Lake and, therefore, ported. Therefore, the lower limit of daily brine has higher average air temperatures. Likewise, water temperature fluctuation in modern saline pans is not temperatures at Death Valley are higher than at well known. Great Salt LakeŽ. Fig. 16a . Average surface water Daily water temperature fluctuations have been temperatures in these modern evaporative settings credited with the formation of primary growth bands closely correlate to average local air temperatures. in haliteŽ. Dellwig, 1955; Roedder, 1982 similar in Water temperatures tend to be within 58CŽ lower or scale to the fluid inclusion bands in Nippewalla higher.Ž of air temperatures Eubank and Brough, Group halite. Cloudy, fluid inclusion-rich bands may 1980; Brown, 1995; Roberts and Spencer, 1995; H. develop during faster daytime crystal growth. Rapid Zimmermann, pers. comm.. . So surface water tem- halite crystal growth in modern saline pans has been peratures are good proxies for local air temperatures observed to start during early afternoons when high- "58C. est air and water temperatures are reached, and Modern surface air temperature fluctuates on both continue through early evenings. Clear, fluid inclu- annual and diurnal scales, just as surface water tem- sion-poor bands presumably form as crystal growth peratures doŽ. Fig. 16 . Observed fluctuations in pale- slows greatly upon air and temperature cooling dur- otemperatures from ancient evaporites may reflect ing nights or early mornings. This theory has led daily andror seasonal trends in ancient air tempera- evaporite workers to interpret each 100's of mmto tures. mm-thick cloudy±clear couplet as a daily time line. The homogenization measured in the Nippewalla This may be more applicable to chevron crystals Group haliteŽ. 218Cto508C suggest that, during the than to cumulates because most cumulates form mid Permian, the midcontinent region of North within a few hours and may have formed several America may have had air temperatures of approxi- cloudy±clear couplets during that timeŽ see discus- mately 218Cto508C. These ancient surface water sion in Roberts and Spencer, 1995. . Alternatively, it and air temperatures are like those at some modern 126 K.C. Benison, R.H. GoldsteinrChemical Geology 154() 1999 113±132

Fig. 16. Comparisons between shallow surface water temperatures and air temperatures in modern evaporative environments.Ž. a Average air and water temperaturesŽ. on a seasonal scale at Death Valley, CA Ž Roberts and Spencer, 1995 . are quite similar, as are those at Great Salt Lake, UTŽ.Ž.Ž.Ž. Eubank and Brough, 1980 . b Specific air and water temperatures on a daily scale at Death Valley, CA Brown, 1995 and at Great Inagua, BahamasŽ. H. Zimmermann, pers. comm. also exhibit some similarities. Open symbols represent air, filled symbols stand for water.

evaporite settings such as Death Valley, CA, Salina days in modern evaporative environments. The inclu- Omotepec, Baja CA, Quidam Basin, China, and sions with the highest temperaturesŽ situated at the Lake Magadi, KenyaŽ Table 1; Eugster, 1970; Casas cloudy chevron bases. may have been trapped in and Lowenstein, 1989; Casas et al., 1992; Brown, early afternoon, when water and air was at its 1995; Roberts and Spencer, 1995. . warmest. The inclusions with the lowest tempera- It is difficult to know the seasons during which turesŽ. located at the tops of cloudy chevrons may the Nippewalla Group halite precipitated. In modern have been trapped as halite grew in the early evening. saline pans, spring and summer are seasons of high The few measurements made in the clear parts of evaporation and halite precipitation, with desiccation chevron bands show temperatures that are intermedi- of the saline pan commonly occurring in the hottest, ate between the lowsŽ at top of the next lower cloudy driest part of the summer, and flooding occurring band.Ž and the highs at the base of the next higher during the winter and early spring. However, these cloudy band; Fig. 14. . These inclusions may have desiccation and flooding events do not always occur formed in the morning as temperatures were increas- on a regular, once-a-year timetable. The homoge- ing. We theorize that each cloudyrclear chevron nization temperatures measured in the Nippewalla couplet may have formed in a single Permian day Group halite may best match late spring and late and may indirectly represent corresponding air tem- summer water and air temperatures for modern envi- peratures for some of the Permian day and perhaps ronmentsŽ. Figs. 11 and 16a , but the seasons of some of the Permian evening. However, it is likely halite growth for this Permian example are still that our data is not a complete record of the total unknown. range of day±night temperature fluctuation because Homogenization temperature trends observed inclusions may not have been trapped during cooler across cloudy chevron bands in the Nippewalla Group parts of the diurnal cycle. halite may represent daily temperature fluctuations. The fluid inclusion paleotemperature data ob- The range of decrease in temperature across cloudy tained for the Nippewalla Group are close proxies bandsŽ. 68 to 268C closely matches some water and for Permian air temperatures for specific localities at air temperature changes over the course of single specific times. In fact, it seems more correct to call K.C. Benison, R.H. GoldsteinrChemical Geology 154() 1999 113±132 127 these homogenization temperatures `paleo weather' temperatures to 108C. Although the Nippewalla data rather than paleoclimate data. Group halite was deposited in lakes, most were small, ephemeral lakes that most likely had less of an 7.4. Comparison with paleoclimate models effect on the average air temperatures than extensive, deep lakes would. The Nippewalla Group paleotem- Geologic evidence, such as paucity of coals and peratures of 218Cto508C suggest that the halite was abundance of evaporites and aeolian siliciclastics, deposited in a climate similar to that predicted by suggests that the midcontinent region of North this model. America was hot and arid during the mid±late Per- The comparison of Nippewalla Group data to mianŽ Dubiel and Smoot, 1994; Francis, 1994; Faure another paleoclimate model also shows some agree- et al., 1995. . Palegeographic reconstructions support ment. A model called PALEOCLIMATE was em- this general paleoclimate for the environment of the ployed to predict ancient surface air temperatures Nippewalla GroupŽ Holdoway, 1978; Scotese and and superimpose them over detailed paleogeographic McKerrow, 1990. . These evaporites and red beds reconstructionsŽ. Golonka et al., 1994 . Average air were deposited near the Equator in closed basins temperature outputs for the paleogeographic setting characterized by low elevation and low topographic of the Nippewalla Group in Kansas are 258Cto308C relief bordered on several sides by higher elevation for the Early PermianŽ. 277 m.y.a. and 258C for the areas of uplift. Although proximity to the Equator Late PermianŽ. 255 m.y.a. . Although the Nippewalla usually suggests humid conditions, this area was Group paleotemperatures are slightly higher than probably a desert due to highlands-induced rain these model temperatures, there may be a summer shadow effect or to dry air masses travelling a long bias in our data. The local climate under which the distance over landŽ. Golonka et al., 1994 . Nippewalla Group halite was deposited was probably Paleoclimate simulation models have been devel- similar or slightly warmer than the climate that this oped for the Permian. These models incorporate:Ž. 1 model predicts. paleogeographic reconstructions,Ž. 2 presence of geo- It is difficult to compare paleoclimate model out- logic climatic indicators such as coals, evaporites, put with paleoclimate data. The models are run for and bauxites, andŽ. 3 knowledge of modern climate certain times that may not correspond to the exact processes. Some shortcomings are gaps in our age of the poorly dated Nippewalla Group. It should knowledge of paleogeography and paleoenviron- also be noted that these model temperatures are ments as well as lack of quantitative paleoclimate average annual or seasonal air temperatures for a data as ground truth for the climate simulations. The large region, whereas the surface water paleotemper- detailed localized and quantitative paleoclimate data, atures reflect indirect air temperatures for a highly such as the air paleotemperatures we provide, can be localized area over more specific time periods. How- used to test and modify paleoclimate simulation ever, it is possible that these two paleoclimate mod- models. els and the surface water paleotemperatures are both Paleotemperatures are an output of many paleocli- valid. Only the accumulation of quantitative paleoclimate simulation models. The Kutzbach and Ziegler mate data from more rocks and the development of Ž.1993 Late Permian climate model applied knowl- more detailed paleoclimate models will allow better edge about modern atmospheric dynamics to infor- evaluations to be made. mation about Late Permian land±ocean boundaries, topography, and inland lakes and seas in order to determine past surface air temperatures. At the ap- 8. Conclusions proximate paleogeographic location of the Nippe- walla Group in Kansas, summer temperatures of This research:Ž. 1 shows that primary fluid inclu- 408Cto508C and winter temperatures of 158C were sions in some ancient halites record ancient surface predicted if this region had no extensive lakes. The conditions;Ž. 2 evaluates a method for measuring presence of extensive lakes would decrease the sum- homogenization temperatures of fluid inclusions in mer temperatures to 258Cto308C and the winter ancient halites;Ž. 3 determines mid Permian surface 128 K.C. Benison, R.H. GoldsteinrChemical Geology 154() 1999 113±132 water temperatures and describes daily temperature Acknowledgements fluctuations; andŽ. 4 relates surface water temperatures to air temperatures and discusses significance This study benefitted greatly from discussions to Permian paleoclimate. about fluid inclusions in halite held with Sean Bren- Comparison of depositional and early diagenetic nan, Christopher Brown, Jianren Li, Tim Lowen- features in the Nippewalla Group halite with modern stein, Dave Newell, Jim Reynolds, Sheila Roberts, evaporites indicates growth from shallow surface and Ed Roedder. KCB is especially indebted to Tim waters in an ephemeral lakersaline pan setting. Pri- Lowenstein for introducing her to fluid inclusions, mary fluid inclusions along growth bands formed as evaporites, and paleoclimate. Phil Brown is thanked the halite precipitated from these shallow surface for his careful review of the manuscript. Financial brines. Careful evaluation of the homogenization and logistical support from the Geology Department data shows that the fluid inclusions in the Nippe- at the University of Kansas, the Kansas Geological walla Group halite have not undergone thermal Survey, Phillips Petroleum, and student research reequilibration while in the lab or in nature and are grants to KCB from Sigma Xi and the Geological representative of Permian parent surface brines. Shal- Society of America are gratefully acknowledged. low water origin eliminates the need for pressure correction. The surface water temperatures determined from primary fluid inclusions using the `cooling nucleation' method range from 218Cto508C. So, during the mid Permian, shallow lake waters of these temperatures existed in western Kansas. These Permian Appendix A surface water temperatures are proxies for ancient air temperatures; they compare favorably to average re- Homogenization temperature data for primary gional temperatures for the Permian predicted from fluid inclusions in Nippewalla Group halite. Th's paleoclimate simulation models. The mid Permian listed are the first Th measured for a particular climate of this locale was not unlike the climate in inclusion. Reproduced Th values are not listed here, its modern counterparts. but are all within 18C of first Th run. The fluid inclusions also preserve at least part of the range of day±night temperature variation, indi- Sample FIA Th, 8C size, mm X cating ranges of at least 68 to 268C. Detailed, quanti- An 1365 FIA 1 33.7 15 tative paleoclimate data, such as these Permian Chevron 33.8 12 Nippewalla Group halite surface water temperature, 33.5 4 provide significant input for paleoclimate models. FIA 2 34.0 25 Quantitative summer temperatures and diurnal tem- Chevron 33.9 8 perature ranges cannot be obtained by traditional 34.8 20 geological paleoclimate indicators, such as presence 35.0 24 or paucity of coals, evaporites, or aerolian siliciclas- 35.3 10 tics. Gathering ancient paleoclimate data, such as 35.0 9 those produced in this study, are essential in order FIA 3 40.7 19 for us to achieve a broader understanding of climate Chevron 42.1 7 through geologic time. Fluid inclusions, especially 40.4 5 those in evaporite minerals, should be a key target 40.5 3 for paleoclimate studies. 41.1 5 Presented at the sixth biennial Pan-American 40.4 6 Conference on Research on Fluid Inclusions 41.8 8 Ž.PACROFI VI held May 30±June 1, 1996 at The 42.2 3 University of Wisconsin in Madison, WI, USA. K.C. Benison, R.H. GoldsteinrChemical Geology 154() 1999 113±132 129

Appendix A Ž.continued Appendix A Ž.continued 41.5 6 FIA 4 28.1 28 40.6 9 Chevron 27.6 30 FIA 4 41.9 30 30.0 16 Chevron 39.7 55 28.2 15 40.6 7 FIA 5 29.4 12 41.0 5 Cumulate 28.1 125 FIA 5 45.2 6 28.9 18 Chevron 44.8 11 Cumulate FIA 6 33.8 380 XY Chevron FIA 6 35.8 9 An 1396 6 FIA 1 23.1 25 Chevron FIA 7 40.9 15 Chevron 28.4 12 FIA 8 44.5 25 FIA 2 27.5 14 Chevron 44.2 25 Chevron 27.0 18 43.1 9 FIA 3 37.2 38 43.6 15 Chevron 35.8 91 43.5 12 36.6 18 43.7 12 37.0 27 43.9 15 36.5 20 43.8 10 Chevron FIA 4 42.7 26 45.2 3 FIA 5 39.2 21 FIA 9 41.6 30 Chevron 39.5 30 Chevron 41.3 7 39.5 30 Chevron FIA 10 46.1 10 Chevron FIA 6 41.2 45 FIA 11 38.9 22 FIA 7 35.0 13 Cumulate 38.1 20 Chevron 34.6 9 39.2 9 37.9 6 FIA 12 37.6 20 Chevron FIA 8 38.8 10 Cumulate 35.5 10 Chevron FIA 9 40.4 9 38.4 6 41.8 16 38.1 5 40.7 9 X FIA 13 35.4 8 An 1406 FIA 1 48.2 11 Cumulate 36.6 3 Chevron 47.1 3 36.5 15 47.5 5 FIA 14 34.9 14 49.8 31 Cumulate 34.6 6 45.4 16 34.0 10 49.7 8 32.2 9 FIA 2 27.5 4 X An 1395 FIA 1 34.5 46 Chevron 24.5 25 Chevron 32.7 27 24.9 44 37.9 25 27.8 16 34.1 11 FIA 3 23.6 15 32.5 17 Chevron 23.6 32 34.8 20 24.3 15 Chevron FIA 2 36.3 45 FIA 4 31.0 15 FIA 3 40.6 27 Chevron 30.6 19 Chevron 40.4 10 FIA 5 35.9 28 40.9 20 Chevron 37.7 22 130 K.C. Benison, R.H. GoldsteinrChemical Geology 154() 1999 113±132

Appendix A Ž.continued Appendix A Ž.continued FIA 6 28.3 14 35.8 95 Chevron 25.0 53 38.3 27 27.3 24 34.9 11 28.8 45 35.9 18 FIA 7 31.6 30 37.4 15 Chevron 35.3 18 FIA 4 25.5 61 36.4 22 Cumulate 31.8 32 XY FIA 8 45.4 27 AEC 1624 6 FIA 1 30.9 16 Chevron 46.3 15 Cumulate 30.7 18 48.1 58 27.4 25 FIA 9 38.2 6 27.2 34 Cumulate 43.5 15 FIA 2 33.3 25 40.6 11 35.6 12 FIA 10 32.9 22 FIA 3 37.8 14 Chevron 32.2 25 Cumulate 36.6 10 33.4 8 38.4 25 34.1 11 FIA 4 44.7 16 FIA 11 43.5 33 Cumulate 42.3 25 Chevron 41.9 12 42.2 21 FIA 12 38.2 12 42.1 28 Chevron 38.6 10 43.4 35 40.1 8 FIA 5 28.8 16 40.9 10 Cumulate 28.5 18 39.8 11 29.3 13 38.6 4 30.8 10 37.9 9 32.5 7 XY An 1406 2 FIA 1 28.6 20 29.7 15 X Cumulate 31.9 15 AEC 1627 FIA 1 42.1 14 FIA 2 40.4 18 Cumulate 43.4 10 Cumulate 35.7 12 43.9 35 XY An 1406 9 FIA 1 31.6 25 41.9 21 Cumulate 30.4 26 42.3 36 37.8 54 44.2 44 38.7 56 43.3 47 34.5 39 40.0 27 37.1 36 40.1 30 34.9 9 FIA 2 32.4 9 34.8 18 Cumulate 32.6 14 38.2 92 FIA 3 35.9 10 FIA 2 40.6 16 Cumulate 37.4 7 Cumulate 42.5 48 36.6 27 44.6 22 37.6 15 43.4 20 FIA 4 46.4 3 FIA 3 34.6 45 Cumulate 45.9 4 Cumulate 35.7 30 FIA 5 36.8 12 36.2 51 Cumulate 36.9 9 K.C. Benison, R.H. GoldsteinrChemical Geology 154() 1999 113±132 131

Appendix A Ž.continued and paleoclimatic implications from a salt core of Badwater Basin, Death Valley, California. M.A., SUNY at Binghamton. 35.9 10 Carpelan, L.H., 1958. The salton sea: physical and chemical 33.3 5 characteristics. Limnology and Oceanography 3, 373±386. 36.4 8 Casas, E., 1987. Diagenesis of salt pan halite. M.A., SUNY at 33.1 10 Binghamton. XY Casas, E., Lowenstein, T.K., 1989. Diagenesis of saline pan AEC 1627 6 FIA 1 32.2 15 halite: comparison of petrographic features of modern, Quater- Chevron 33.4 21 nary, and permian halites. Journal of Sedimentary Petrology Chevron FIA 2 41.8 45 59, 724±739. Chevron FIA 3 45.1 24 Casas, E., Lowenstein, T.K., Spencer, R.J., Pengxi, Z., 1992. FIA 4 44.7 10 Carnalite mineralization in the nonmarine, Quidam Basin, China: evidence for the early diagenetic origin of potash Chevron 47.1 12 evaporites. Journal of Seidmentary Petrology 62, 898. FIA 5 27.2 92 Dellwig, L.F., 1955. Origin of the Salina Salt of Michigan. Chevron 31.5 20 Journal of Sedimentary Petrology 25, 83±110. FIA 6 32.8 35 Dubiel, R.F., Smoot, J.P., 1994. Criteria for interpreting paleocli- Chevron 35.0 36 mates form red bedsÐa tool for Pangean reconstructions. In: Embry, A.F., Beauchamp, B., Glass, D.J.Ž. Eds. , Pangea: 34.6 12 Global Environments and Resources, Vol. 17, Canadian Soci- Chevron FIA 7 21.4 45 ety of Petroleum Geologists Memoir, pp. 295±310. FIA 8 30.1 24 Eubank, M.E., Brough, R.C., 1980. The Great Salt Lake and its Chevron 30.4 18 influence on the weather. In: Gwynn, J.W.Ž. Ed. , Great Salt 31.8 46 Lake: A Scientific, Historical, and Economic Overview, Vol. 116, Utah Geological and Mineralogical Survey Bulletin, pp. FIA 9 38.9 12 279±283. Chevron 35.9 18 Eugster, H.P., 1970, Chemistry and origin of the brines of Lake FIA 10 45.3 48 Magadi, Kenya: Mineralogical Society of America Special Chevron 44.9 25 Paper 3, pp. 213±235. Faure, K., de Wit, M.J., Willis, J.P., 1995. Late Permian global 43.8 17 13 coal hiatus linked to C-depleted CO2 flux into the atmo- FIA 11 35.8 23 sphere during the final consolidation of Pangea. Geology 23, Chevron 41.2 45 507±510. 37.1 15 Fay, R.O., 1964. The Blaine and related formations of northwest- FIA 12 32.9 21 ern Oklahoma and southern Kansas. Oklahoma Geological Chevron 31.8 40 Survey Bulletin, 98. Fay, R.O., 1965, Geology and mineral resources of Woods County, 32.6 45 Oklahoma. Oklahoma Geological Survey Bulletin, 106. 33.2 15 Fay, R.O., Ham, W.E., Bado, J.T., Jordan, L., 1965. Geology and 31.6 35 mineral resources of Blaines County, Oklahoma. Oklahoma Geological Survey Bulletin, 89. Francis, J.E., 1994. Palaeoclimates of Pangea-geological evidence. In: Embry, A.F., Beauchamp, B., Glass, D.J.Ž. Eds. , Pangea: Global Environments and Resources, Vol. 17, Canadian Soci- References ety of Petroleum Geologists Memoir, pp. 265±274. Goldstein, R.H., Reynolds, T.J., 1994. Systematic of fluid inclusions in diagenetic minerals. SEPM Short Course 31, Tulsa. Baars, D.L., 1990. Permian chronostratigraphy in Kansas. Geol- Golonka, J., Ross, M.I., Scotese, C.R., 1994. Phanerozoic paleo- ogy 18, 687±690. geographic and paleoclimatic modeling maps. In: Embry, A.F., Benison, K.C., 1995. Permian surface water temperatures from Beauchamp, B., Glass, D.J.Ž. Eds. , Pange: Global Environ- Nippewalla Group halite, Kansas. Carbonates and Evaporites ments and Resources, Vol. 17, Canadian Society of Petroleum 10, 245±251. Geologists Memoir, pp. 1±47. Brookins, D.G., Naeser, C.W., 1971. Age of emplacement of Gornitz, V.M., Schreiber, B.C., 1981. Displacive halite hoppers Riley County, Kansas, kimberlites and a possible minimum from the Dead Sea: some implications for ancient evaporative age for the Dakota Sandstone. Geological Society of America deposits. Journal of Sedimentary Petrology 51, 787±794. Bulletin 82, 1723±1726. Ham, W.E., 1960, Middle Permian evaporites in southwestern Brown, C.B., 1995. Sedimentology, fluid inclusion geochemistry Oklahoma. 21st International Geological Congress Report, 12. 132 K.C. Benison, R.H. GoldsteinrChemical Geology 154() 1999 113±132

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