THE CGRRELQWON SF CENCINNATEAN EN’JiRONMENTS BY SFECTRCH‘SRAPHKC ANALYSES OF ASSOCIATfifl FC‘SSELS "Y’I’wsis fit}! an Begt’m mt M. S. MECHEGAN STATE COLLEGE Duane C. Ushré 1954 THESIS This is to certify that the thesis entitled mm C.” presented by The Correlation of mncinmtian Environments by Spectrographic Analyses of Associated Fossils has been accepted towards fulfillment of the requirements for ii.— degree in m Teflmafl/wa Major professorV Date Septe-ber 30. 1951; 0-169 MSU RETURNING MATERIALS: Place in book drop to remove this checkout from LIBRARIES .—_ your record. FINES will be charged if book is returned after the date * stamped below. ‘33 2g". 058336-4991 new ‘5 5?? THE CORRELATION OF CINCINNATIAN ENVIRONMENTS BY SPECTROGRAPHIC ANALYSES OF ASSOCIATED FOSSILS By DUANE c . UHRI A THESIS Submitted to the School of Graduate Studies of Michigan State College of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Geology and Geography 195“ ACKNOWLEDGEMENTS The author's sincere appreciation is extended to Dr. B. T. Sandefur for his assistance and encouragement during this investigation. It was under his supervision that this report was prepared. This investigation would not have been possible without access to the proper equipment. The author wishes to express his sincere gratitude to Dr. E. J. Miller for permitting him to use the spectrographio laboratory of the Agricultural Chem- istry Research Station and for introducing him to their spec- troscOpist, Ralph Bacon. Mr. Bacon gave considerable assist- ance and a great deal of his time in helping the author ob- tain the spectrographic data for this problem. The author is also indebted to the following people who have given freely of their time and advice in this study: Dr. W. H. Shideler of Miami University at Oxford, Ohio for iden- tifying and supplying brachiopod specimens for the analyses; Dr. W. A. Kelly for his information and advice concerning stratigraphy and lithology; Dr. S. G. Berquist for his criti- cal review and editing of the manuscript; and his wife for her supervision, assistance, and constructive criticisms in regard to the various chemical procedures. fir $4"!‘ 0. -.‘ .4 THE CORRELATION OF CINCINNATIAN ENVIRONMENTS BY SPECTROGRAPHIC ANALYSES OF ASSOCIATED FOSSILS Duane C. Uhri ABSTRACT Biogeochemical methods of research have become increas- ingly important in recent years and have aided geologists in solving numerous problems. One such problem pertains to the Cincinnati Arch area. Some geologists argue that during Gin- oinnatian time, two arms of a sea existed in this area and that the formations from the Greendale through the Arnheim were deposited in the southern branch and those formations immediately above the Arnheim in the northern branch. Others claim that the two arms of the sea were united and remained as one continuous sea throughout this time. If the former were correct, it would not be improbable that the composi- tion of the water in the two branches differed slightly in dissolved constituents. If the latter were true, it seems likely that the sea water would have had a uniform distri- bution of dissolved material except for minor local varia- tions. Since many marine organisms have the capacity to frac- tionate elements to a certain degree during their growth stages and since the raw materials used in the formation of their skeletal frameworks are extracted mainly from the sur- rounding sea water, the presence of a particular organism in a given locality and the chemical composition of its skele- ton should be indicative of its environment. If one were to find that for a particular species of marine organism the compositions of several members remained essentially the same or that there existed a certain ratio of component elements characteristic of that species for a given set of environ- mental conditions, a large difference in the compositions or elemental ratios of several specimens would suggest the ex- istence of considerably different environments for the vari- ous members examined. Attempts were made at solving the Cincinnati Arch prob- lem by means of investigations into the compositions of sup- posedly northern and southern fossilized brachiOpods which showed no evidences of diagenetic alterations. BrachiOpods were chosen as the class of organisms to be analyzed for sev- eral reasons: 1) brachiopods were sessile-benthonic forms and are probably found in marine strata in the immediate vicinity of their former habitat; 2) brachiopod genera and species can be identified with much greater certainty and ease than many other types of organisms; 3) there is considerable skeletal material in relation to the size of the individual; and 4) brachiOpod shell punctae and tubules produce only a limited amount of porosity thereby reducing possibilities of alter- ation by diagenetic processes. Spectrographic analyses and chemical tests yielded the following results: 1) the major and trace elements in all the brachiOpod specimens were similar; 2) the quantities of cer— tain elements varied between specimens; 3) all of the brachi- Opods belonged to the calcareous group; A) the fossils con- tained less than 1.5 5% Mg“ by weight; and 5) the ratios of MgCOB/CaCO3 differed between the same species as well as be- tween different genera and species. The analyses of certain specimens seemed to support the theory that there had been two branches of the sea in the Cincinnati Arch area. Other fossil analyses gave rise to much uncertainty in such an interpretation. si— TABLE OF CONTENTS Page INTRODUCTION ....................................... l Biogeochemical Research ......................... 1 Cincinnati Arch.Area ............................ 2 Fractionation of Elements by Marine Organisms ... 3 Methods of Investigating the Cincinnati Arch Problem ....................................... 4 APPARATUS, METHODOLOGY, AND DATA 5 Selection and Source of Materials ............... 5 Preparation of Specimens for.Ana1ysis ........... 8 Determination of Constituent Elements ........... 9 Relationship between CaCO3 and MgCO3 in Brech- iopods ........................................ 9 Trial Magnesium and Calcium Determinations ...... 10 Quantity of Sample Required ..................... 10 Procedure for C03= Determinations ............... 11 Procedure for Spectrographic Analyses of Mg" Ion Concentrations ............................ lb ANALYSIS OF DATA ................................... #3 SUMMARY AND CONCLUSIONS ............................ 51 BIBLIOGMPHY .....OOOOOOOOOOOOOOO0.0000000000000000. 53 Table I. II. III. IV. V. VI. VII. VIII. TABLES Ordovician BrachiOpods and Stratigraphic Relationships 00.00.000.000...00.0.0.0...O Titrations with Hydrochloric Acid .......... Percentage Weight Determinations for 0038... Standard Magnesium Solutions ............... Step Sector Data for Plates b, 5, and 6 .... Working Curve Data for Plates b, 5, and 6 .. Spectrographic Data for Fossil Materials ... Non-internal Standard Data and Percentages Mg**0bta1ned OOOOOOOOOOOOOOOOOOOO0.000... ”Curved“ Working Curve Data and Percentages Mg‘+ Obtained ......OOOOOOOOOOOOO0.00.0... Relative Intensity Mg/Ca Ratios for Plates u, 5’ and-6 ............0................. Page 15 16 18 18 25 29 35 37 39 Figure H O \Omfl0\\nl—*UN O 11. 12. 13. ILLUSTRATIONS Collection sites of brachiopod specimens ... Apparatus for CO3‘ determinations .......... Calibration curve for plate a .............. Calibration curve for plate 5 .............. Calibration curve for plate 6 .............. Working curve for plate # .................. Working curve for plate 5 .................. Working curve for plate 6 .................. Non-internal standard working curve for platel‘oeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee ”Curved“ working curve for plate # ......... Egg/RICa bar graph composite for plates ,an 00.0.0.........OOOOOOOOOOOOOO. Block diagram illustrating on—lap of sedi- ments .00..........OOOOOOOOOOOOO00.0.00... Ordovician strata and associated brachiopods Page 12 21 22 23 26 27 28 34 36 an #6 #9 INTRODUCTION Biogeochemical Research In recent years, many of the investigations into paleon- tological problems have been concerned with biogeochemical methods of research. A number of these methods deal with the chemical and isotOpic compositions of marine fossils, present- day marine organisms, and sediments. Examples which may be cited are: l) the oxygen isotope studies of carbonate-secret- ing marine organisms by H. C. Urey, S. Epstein, and H. A. Lowenstam to obtain paleotemperature relationships; 2) the investigations of Keith E. Chave into the biogeochemistry of magnesium in calcareous skeletal material to arrive at a cor- relation between magnesium content and skeletal mineralogy, water temperature, phylogenetic level of the organism, salin- ity and depth of the water, and the age or size of the indi— vidual; 3) the effect of chemical scavengers of marine waters as observed by E.D. Goldberg; and A) the determination of the origin and classification of chemical sediments in terms of the oxidation-reduction potentials and hydrogen-ion concentra— tions of their environments by Krumbein and Garrels. -2- It seems likely that biogeochemistry will be the answer to Various paleontological problems and help to support or to weaken numerous controversial theories. Cincinnati Arch Area One such controversy pertains to the Cincinnati Arch area. During the early part of the Paleozoic era, most of the continent of North America Was covered by shallow seas which, due to their shallcwness, fluctuated areally to a great ex— tent. Some geologists argue that during Cincinnatian time, a northern and a southern arm of one of these seas existed in this arch area and that the two branches were separated by an east-west trending barrier in the vicinity of southwest- ern Ohio. Others claim that no barrier existed but that the two arms of the sea were united and remained as one contin- uous sea throughout this time. If the former were correct, it would not be improbable that the composition of the water in the two branches dif- fered slightly in dissolved constituents. If the latter were true, it seems likely that the sea water would have had a uniform distribution of dissolved material except for minor local variations. Fractionation of Elements by Marine Organisms It is a well—known fact that many marine organisms have the capacity to fractionate elements to a certain degree dur- ing their growth stages. V. T. Bowen and D. Sutton have found that large amounts of nickel are extracted from sea water by sponges. Numerous articles mention that iodine is much more concentrated in various seaweeds than in the surrounding en- vironment. According to E. D. Goldberg, strontium and yttri- um are extracted from marine waters by red and green algae, vanadium by the mucus of tunicates, and silicon by sponges. H. C. Urey, S. Epstein, and H. A. Lowenstam have discovered that belemnites incorporate O16 and 018 into their skeletons in a definite ratio. Therefore, since a particular marine organism can exist only under certain environmental conditions because the raw materials used in the formation of its skeletal framework are extracted mainly from the surrounding sea water, the presence of that organism in a particular locality and the chemical composition of its skeleton should be indicative of its environment. If one were to find that for a particular species of marine organism the compositions of several mem- bers remained essentially the same or that there existed a certain ratio of component elements characteristic of that species for a given set of environmental conditions, a large difference in the compositions or elemental ratios of several -h— specimens would suggest the existence of considerably dif- ferent environments for the Various members eXamined. This seems possible since H. A. Lowenstam and others have found that the ecology of many marine organisms indicate a class- distinct mineralogical selection related to their modes of life. Methods of Investigating the Cincinnati Arch Problem A solution or an aid to the solution of the previously mentioned controversy might be obtained by means of investi- gations into the compositions and elemental ratios of suppos- edly northern and southern fossilized fauna which show no ev- idences of diagenetic alterations. The Spectrographic deter- mination of the existence of trace elements in the former group and of the absence of the same elements in the latter group would suggest that there had been two arms of the sea, whereas the detection of the same elements in both groups would support the idea of a continuous sea. Another method would be to spectrographically determine the ratios of mag- nesium carbonate to calcium carbonate for the various members since the magnesium content increases at the expense of the calcium and is affected by the temperature, salinity, and depth of the water. These were the two methods attempted by the author and a discussion of the methodology, apparatus, and data is now in order. APPARATUS, METHODOLOGY, AND DATA Selection and Source of Materials BrachiOpods were chosen as the class of organisms to be used for several reasons: 1) brachiopods were sessile-ben- thonic forms and are probably found in marine strata in the immediate vicinity of their former habitat; 2) brachiOpod genera and species can be identified with much greater cer- tainty and ease than many other types of organisms; 3) there is considerable skeletal material in relation to the size of the individual; and h) brachiopod shell punctae and tubules produce only a limited amount of porosity thereby reducing possibilities of alteration by diagenetic processes. The specimens were obtained from and identified by W. H. Shideler of Miami University at Oxford, Ohio. The relation- ships between the geological formations and the specimens are shown in Table I.‘ According to Professor Shideler, the sites of their collections are as mapped in Figure 1. He also stated that many believe the formations from the Green- dale through the Arnheim were deposited during the invasion ...-— e The reference numbers Opposite the generic names will be used hereafter instead of the actual names. u... a TABLE I ORDOVICIAN BRACHIOPODS AND STRATIGRAPHIC RELATIONSHIPS Strata Brachiopods Series Group Formation Genus and Species No. Cincinnatian Richmond Elkhorn Whitewater— Rhynchotrema dentatum 17,18 Saluda Liberty Rafinesquina alternate 13,1h Waynesville Rafinesquina alternate 11,12 Leptaena richmondensis 7,8 Arnheim Rhynchotrema dentatum 15.16 Rafinesquina alternate 9,10 Leptaena richmondensis 5,6 Maysville Mt. Auburn Corryville Bellvue Fairmount Orthorhynchula linney 3,h Mt. Hope Eden McMicken Soumhgate Economy Fulton Hohawkian Cynthiana Rogers Gap Gratz Bromley Greendale Orthorhynchula linney 1,2 OLexington KENTUCKY oRowena (3,“) r-"-----------------------------------------1 mess: 3.3.1.304 - , A 50mm $12,13,1h,l7,18) . Oxford 5,6,7,8,9,10,n) OHIO e Cincinnati e Millersburgfl ,2) Loni svill e Fig. 1. Collection sites of brachiopod specimens -8- of the area by the southern branch of the sea and the forma- tions immediately above the Arnheim, during a later invasion by the northern branch, the associated fossils being the re- mains of southern and northern fauna respectively. Preparation of Specimens for Analysis From each group of brachiopods of the same genus, spe- cies, stratum, and collection site, the two specimens which appeared to be the most well preserved were selected for the following investigations. Most of the adhering sediment was removed from the exteriors of the shells after which the foe- sils were washed in distilled water, dried, and pulverized in a steel percussion mortar. The mortar was washed, rinsed with dilute hydrochloric acid, and rewashed with distilled water before breaking up a different shell. The entire mater- ial of each specimen was sieved to less than 100 mesh to produce a homogeneous powder with particles of a fairly uni- form size. During the pulverization, it was observed that the interior cavity between the Valves of each specimen was filled with secondary silica, but no attempt was made to re- move it. Determination of Constituent Elements Small amounts of the fossil powders were placed into the cavities of carbon spectrograph electrodes and, using the Littrow spectrograph, a spectrum between 245C and 3450 A was obtained for each. Detailed studies showed the presence of large amounts of calcium and silicon, some magnesium, alu- minum, sodium, phosphorus, and boron, and traces of lead, zinc, and other elements. The source of the lead and zinc, however, was probably the sieve through which the powders were shaken. The major and trace elements appeared to be the same when the various spectra were compared but a difference in the amounts of certain constituents was observable. Relationship between CaCOB and MgCO3 in BrachiOpods It was then decided to consider the relationships be- tween the CaCO3 and MgCO3 contents of the fossils. Several analyses by F. W. Clarke and W. C. Wheeler (1917) show that there were two types of brachiOpods: 1) those with calcar- eous skeletons and 2) those with a highly phosphatic compo- sition. The calcareous forms contained small amounts of CaSOa and Ca3P208, whereas the phosphatic types were com- posed mainly of Ca3P208 with small quantities of MgCOB, CaCOB, and CaSOh which were similar in magnitude. This made it ..10- necessary to deviate from an entirely spectrographic analy- sis and to employ wet chemical methods for the determina- tion of C03' ion contents since the presence of Ca" ions in the Ca3P208 and CaSOu would affect a spectrographically ob- tained CaCOB/MgCO3 ratio. A wet chemical procedure had to be followed because, of Caco3 and MgCOB, only the Ca“ and Mg“ ion concentrations may be obtained from the usual spectro— graphic procedures. Trial Magnesium and Calcium Determinations So to prepare spectrographic standards within the prop- er range, one-gram samples of several fossil powders were dissolved in dilute hydrochloric acid and diluted to 100 ml. After several minutes of agitation, they were allowed to stand #8 hours to permit the silicates and other insolubles to settle to the bottoms of the flasks. With lithium as an internal standard and solutions of varying Ca“ and Mg" ion concentrations, trial runs showed approximately 20—30 Z Ca“ ion and 0.1-0.6 % Mg" ion concentrations. Quantity of Sample Required The weights of a number of fossil powders approximated ‘- one gram each and, since it was desired to hold down to a minimum any experimental error due to variability in sample -11- sizes, three 0.3 gram samples of each fossil powder were used for analysis. One of these was used in the preparation of a solution for the spectrograph and two were employed for CO3= determinations. Procedure for 003. Determinations The 003"I ion concentration of an individual sample was completely determined before another sample was started. The apparatus is shown in Figure 2 and the procedure followed was similar to that for the usual determination of C03= in a slightly alkaline solution. The 0.3 gram sample of fossil material was placed into a 200 ml. Erlenmeyer flask. To this flask (#1) were added 75 ml. of distilled water. Flasks #2 and #3 each contained 100 ml. of NaOH solution.1 The flasks were placed in their prep- er positions, tightly stoppered, and, after the system had been carefully checked for the leakage of air, 5 ml. of con- centrated sulphuric acid were added slowly.2 After flask #1 - had received the total amount of acid, it was heated to boil- ing. Heat was applied slowly so as to allow the volume of gas bubbling into flasks #2 and #3 to react with the NaOH lNaOH solution = 5 grams wet-weight of NaOH crystals dis- solved in 2 liters of distilled water 232504 was used because of its low volatility as compared with other acids. -12- oneuuunnanoaou amoo_uou naasuegnd..~ .Muh 3 Mesa.— una» humananuo £1 333 :58 cc .3an sedan “My enema on“. any mafia... €an 3 case oaanuna Adv mag A3 9.3.8 2 e93. Sam e. I r ma. “and: Adv 3 1x 3 . CV i , 3 sedan -13- according to: 2NaOH + 002(g) —-—-;-Na2003 4 H20 When it became evident that steam was beginning to pass through the system, the time of completion of the trial was set for 3 minutes thereafter. Flasks #2 and #3 were then removed for titration. To each flask were added 3 drOps of phenolphthalein indicator.3 Dilute hydrochloric acid was added dropwise until the solu— tions reached the phenolphthalein endpoint. The reaction which occurred may be expressed by: HCl + NaOH—-—a-NaCl + H20 HCl + Na2C03 ———4-NaHCO3 4 NaCl and resulted in solutions with a pH of 7. A reading was made on the burette. After each solution had received 6 drops of brom-phenol-blue indicator, it was titrated with dilute hy- drochloric acid of known normality to a blue-gray color with the use of potassium biphthalate (0.1 N) as a color standard for the brom-phenol-blue. Another reading was taken on the burette to determine the quantity of HCl required for the process: HCl + NaHCO3 ———a-nH2C03 4 NaCl during which the pH of 7 was lowered to a pH of h. The moles of HCl required for the titration of the NaHCO3 were equal, 3The solutions were titrated in the same flasks to prevent possible loss of liquid in a transferring procedure. alha therefore, to the moles of C03= ion contained in the solu- tion. Several blanks were run according to the above procedure and it was found that the number of moles of CO3= should be reduced by 0.0002140 moles due to 002 in the NaOH, air, and water.“ The results of these determinations are recorded in Tables II and III. Knowing the quantity of 003' and Mg*’ present, it would not be difficult to calculate the amount of Ca" since the total carbonate consisted of CaCO3 and MgCOB. Procedure for Spectrographic Analyses of Mg“ Concentrations The ideal situation would have been to prepare solutions for the spectrograph from the remaining liquids in flasks #1 of the 003' ion determinations but, due to the possibility of impurities being introduced during the process and due to the precipitation of CaSOu upon dilution, fresh samples of the fossil material were used. A 0.3 gram sample of each fos- sil powder was dissolved in hydrochloric acid and diluted to 100 ml. Since it had been previously found by a trial run that the Mg” ion concentrations varied approximately between 0.1 % “Originally, 3 flasks of NaOH solution were used but the a- mount of 002 in the third flask proved to be negligible 'and only two flasks were employed. -15- TABLE II TITRATIONS WITH HYDROCHLORIC ACID —————r_—______—-—_-_———_______—_—__—————-————- Milliliters of HCl Required‘ Sample Trial 1 1 Trial 2' Flask 2 l Flask 3 I Total 1 Flask 2 l Flask 3 1 Total 1 (a) 30.29 (a) 13.28 (a) h3.57 (a) 32.05 (a) 12.u0 (a) hu.h5 2 (a) 31.58 (a) 13.82 (a) 145.140 (2.) 30.69 (a) 13.77 (a) 1111.16. 3 (b) 32.29 (b) 13.23 (b) “5.52 (b)32.13 (b) 13.06 (b) h5.19 u (c) 22.27 (c) n.51 (c) 26.78 (c) 21.96 (c) 5.33 (c) 27.29 5 (c) 18.01 (c) n.12 (c) 22.13 (c) 17.62 (s) n.62 (c) 22.2u 6 (d) 21.19 (d) 5.95 (d) 27.11. - - .- 7 (e) 26.92 (e) 6.91 (e) 33.83 (e) 25.!13 (e) 8.89 (e) 314.32 8 (f) 27-29 (f) 7-13 (f) 3h.h2 (f) 27-13 (f) 7.86 (f) 3h-99 9 (d) 21mm (d) 7.09 (d) 31.149 (0.) 21+.08 (d) 8.07 (d) 32.15 10 (d) 27.00 (a) 7.1.2 («1) 314.112 (a) 26.05 (a) 7.911 (d) 33.99 11 (e) 28.22 (e) 5.h6 (e) 33.68 (e) 28.13 (e) 6.23 (e) 3h.u6 12 (r) 26.29 (f) 7.60 (f) 33.89 (t) 2u.59 (r) 9.02 (f) 33.61 13 (r) 28.00 (t) 7.01 (f) 35.01 (f) 26.25 (f) 8.12 (r) 3u.37 111 (g) 20-39 (s) 5.36 (2) 25-75 (2) 19-08 (g) 6.39 (g) 25.147 15 (a) 23-37 (3) 5-55 (2) 29-02 (e) 22.12 (a) 7-03 (8) 29-15 16 (g) 18.92 (2) 5-55 (2) 2M7 (2) 18.75 (s) 5.70 (2) 2M5 17 (g) 21.88 (g) 7.11 (g) 28.99 (g) 22M (g) 7.111 (g) 29.85 18 (g) 22.71 (g) 7.11 (g) 29.82 (g) 22.29 (g) 7.13 (g) 29.142 ‘Normalities were: (an-0.0601111. (tn-0.060%, (c)=0.09076. (d)-0.08150, (e)-0.076h5, (OI-0.07687, and (gal-0.08139. PERCENTAGE WEIGHT DETERMINATIONS FOR 003: TABLE III Sample i Difference .Average Holes 00; i by It. 1 1.9 (a) hu.01 m1. 0.0026599 h8.9 2 2.1 (a) nu.93 :1. 0.0027156 50.0 3 0.7 (b) u5.36 n1. 0.0027415 50.6 1+ 1.5 (c) 27.011 ml. 0.002h5‘42 mas 5 0.5 (c) 22.19 r1. 0.0020239 36.2 6 - (d) 27.1u :1. 0.0022119 no.0 7 1.h (e) 3h.08 n1. 0.002605h h7.8 8 1.6 (f) 3h.71 :1. 0.0026682 50.8 9 2.1 (a) 31.82 m1. 0.0025933 u7.6 10 1.2 (d) 3u.21 ml. 0.0027881 51.5 11 1.9 (e) 3h.02 n1. 0.0026008 M7.7 12 0.8 (r) 33.75 m1. 0.00259uu h7.6 13 1.8 (f) 314.69 1111. 0.0026666 119.1 in 1.1 (g) 25.61 111. 0.00208lm 37.1; 15 0.5 (g) 29.09 m1. 0.0023676 u3.1 16 0.1 (g) 2h.u6 al. 0.0019908 35.5 17 2.9 (g) 29.I+2 1111. 0.00239145 113.6 18 1.3 (g9 29.62 mi. 0.002u108 M3.9 -16— -17- and 0.6 3, it was decided that the standards for magnesium should have Mg" ion concentrations of 1.5 5, 1.0 %, 0.? Z, 0.5 x, and 0.1 z. Due to the fact that 10 ml. of fossil solution contained 0.030 grams of fossil powder, 10 ml. of solutions with the above Mg” ion concentrations should con— tain 0.450 mg., 0.300 mg., 0.210 mg., 0.150 mg., and 0.030 mg. of magnesium respectively. A solution for the magnesium standards was prepared by dissolving 0.5 gram Mg003 in 1:1 H01 and diluting to 250 ml. The amounts of magnesium solu- tion necessary to duplicate the Mg" ion concentrations in 10 m1. aliquots of the various solutions are listed in Table IV. Strontium was chosen for the internal standard since it is desirable to use an element which has an ionization potent- ial similar in magnitude to that of the analyzed element. “hat was assumed to be a sufficient amount of strontium solu- tion was used as an internal standard with the magnesium standards and fossil solutions, but it was found that a great— er quantity should have been added for these plates 1, 2, and 3. It was determined by the spectrum analysis of sever- al Sr“ ion concentrations that 8 grams of SrClz' 6 H20 should be dissolved in 1:1 HCl and diluted to 100 ml. in or- der to obtain an internal standard which could be used on a 1 m1.-addition basis. To 10 ml. aliquots of the fossil solutions were added 1 m1. of strontium solution and 5 ml. of distilled water to ~18- TLBLI IV STANDARD MAGNESIUM SOLUTIONS Reference number I II III IV V [Igneuum ion 1.5 ‘1 1.0 $ 0.7 1 0.5 $ 0.1 i concentration Amount of internal 1 m1. 1 m1. 1 m1. 1 :1. 1 all. standard mmt Of mgieeium 0.779 m1. 005.9 ”10 0036‘ WI. 0.259 '1. 0.0? .10 solution .Ancunt of water lu.221 n1. 1h.n81 n1. 1h.636 n1. 1n.7u1 n1. 1h.9k8 n1. ,0” ”lune 16.000 ‘10 16.000 m1. 16.000 ‘1. 16.0w ‘1. 16cm ‘1. Tumm‘v 8T1? SECTOR DATA 10R PLATES h, 5,.AlD 6 Sector number = n l 2 3 11 5 6 7 “ll (1.585)n 1.585 2.512 3.981 6.310 10.00 15.85 25.12 39.81 Plate n 83.0 65.0 no.8 23.8 12.3 7.6 3.8 2.2 Plate 5 90.8 76.0 56.0 29.7 18.0 10.2 5.0 2.6 Percent transmission Plat06 85.7 70.0 l$9.3 27.5 18.3 10.5 5.0 3.7 _19_ make a total of 16 m1. In the preparation of the magnesium standards, the same amount of strontium solution was mixed with the proper amounts of magnesium solution and diluted to 16 ml. Carbon electrodes were then cut and polished so as to reduce their porosity and to assure an even arcing. Three e- lectrodes were made for each fossil solution by evaporating 25 lambda of the solutions on the polished surfaces.5 Each spectrum ranged from 2050 to 3&50 A and was run at 9 amperes direct current for 20 seconds, except the iron spectra, which were 2-second exposures. Each plate included the spec— tra of the 5 magnesium standards, iron through a step sec- tor, and several fossil solutions. The plates were developed according to the usual darkroom procedures and the spectrum lines of Mg 2779.8 and Sr 2931.8 were located for percentage- transmission determinations on the Jarrel-Ash densitometer. Calibration curves and working curves for quantitative analysis may follow a number of patterns and be based on var- ious optical relationships. The calibration curves for these plates were obtained with the aid of a step sector. As in most texts on spectroscopy, Ahrens (1950) includes the equa- tion E = It, where E is the exposure, I is the incident light intensity, and t is the time. If the intermittency ef- fect is considered as negligible, it should be possible to 51 lambda = 0.001 cubic centimeters -20- duplicate a number of exposures, which were made by a con- stant I and varying t, by holding t constant and varying 1. Therefore, E = kt = kI. The result of placing a step sector before the spectrograph slit during the photographing pro- cess is a spectrum which is divided into sections of differ— ent exposures. The sector used had 7 steps for which Io/I = 1.585, where I0 is the intensity of line emission and I is the intensity of the line as actually measured.6 Knowing then, that a particular step had an exposure which was 1.585 times that of the preceding step, a calibration curve was pre— pared for each plate by plotting the Log % transmission of the line Fe 2832.83 vs. Log (1.585)“, where n is the step number. Figures 3, h, and 5 show these curves and Table V lists their data. The percentage-transmissions of the Sr 2931.8 and Mg 2779.8 lines were determined for the standard magnesium sam- ples and the fossil solutions. The logarithms of the rela- tive intensities of these lines were then obtained by locat- ing the percentage-transmissions on the ordinate of the pr0p- er calibration curve and reading the relative intensities on the abcissa. The working curves for the quantitative deter— mination of the magnesium contents resulted from plotting the ratios of the relative intensities of the Mg 2779.8 lines of 6The step sector may be regarded as having 8 steps if com- plete exposure is counted as a step. 100’ Percent Transmission 8 I 111111 I I -21.. 10 20 30 Relative Intensity neL uuL 1: \n Fig. 3. Calibration curve for plate N Percent Transmission I l L l l l u 5 10 20 Relative Intensity Fig. ‘4. Calibration curve for plate 5 -22- Percent Transmission 1 l 1 I L l -23- L l Fig. 5. 5 10 20 Relative Intensity Calibration curve for plate 6 30 lK350 -2u_ the standard magnesium solutions to the relative intensi— ties of the Sr 2931.8 lines in the same spectrum vs. the per- centage Mg“ ion concentrations as in Figures 6, 7, and 8.7 According to theory, by locating the RI Mg”/RI Sr*‘ ratios for the fossil solutions on the curves, one may obtain the percentage magnesium ion concentrations for these solutions.8 Since three portions of the same fossil material were run separately, the values obtained for each magnesium ion concentration should be similar in magnitude and a measure of the accuracy of the method. However, the results show consid- erable deviations. Some believe that such deviations or spreads of points for a single sample are due to very low con- centrations of the analyzed element. Ahrens (1950) shows how the reproducibility of the relative intensities of K “on? varies with the concentration of K20. This may have been the case here. The standard deviation from the mean value of each solution was as shown in Table VII. The average standard devi- ation was t 20.1 %, suggesting that Sr 2931.8 was possibly not a practical line to be used with Mg 2779.8. A similar procedure was then attempted, omitting the in- ternal standard and producing a working curve by plotting the logarithm of Ring vs. the Mg“ ion concentration. Providing that the conditions under which each sample is arced are 7See Table VI. 88cc Table VII. -25- w v: IORKING 0mm nun r011 PLATES 1., 5, AND 6 r Percent Relative Plats Standard Percent transmission intensity Log £118 “8” Sr I Mg Sr I u; er u 1 1.5 52.3 28.8 3.18 5.25 0.2180 11 1.0 53.0 1111.3 3.15 3.73 0.0731; 111 0.7 146.8 39.0 3.56 11.13 0.0015 IV 0.5 113.2 119.0 3.81 3.110 «0.0496 v 0.1 38g 61.7 11.18 2.69 -O.lfl1 5 I 1.5' 146.9 26.6 14.53 7.10 0.1952 11 1.0 511.0 38.9 3.97 5.35 0.1296 In 0.7 38.0 36.3 5.145 5.67 0.0172 IV 0.5 38.6 142.6 5.35 11.95 -0.0338 v 0.1 39.3 59.0 5.29 3.59 -0.168h 6 I 1.5 57.2 36.5 3.29 5.15 0.19% 11 1.0 148.5 111.5 8.00 11.60 0.0607 In 0.5 118.2 52.0 11.02 3.0+ -o.ol+31 v 0.1 53.5 79.9 3.62 1.93 -0.2731 -26- 0.2 - 0.1 L Lee slug/m8, .° 0 -0.1 ’ 0.1 0.5 0.7 1.0 1.5 $115“ Fig. 6. Working curve for plate h -27- Oea F 0.1 P to; Ring/Rim. 5’ 0> .001 ' 0.1 0.5 0.7 1.0 115 Mtg“ Fig. 7. 'orking curve for plate 5 -28- 0.2 " .0.1- Log mus/313,. P O -0.1 - -o.2 +- ___L I l 1 0.1 0.5 0.7 1.0 6 Mg“ Fig. 8. lorking curve for plate 6 0.11. m.» 8.0 300.0 mw.m 26 Tu... 0.? 3 u «.2 ... 0.2m .1. u 6.0 5.0 030.0 00.... RA To: 0.? 3 0.090 0.3.. 3.0 88.0.. no; m0; 00: 0.0.. 3 ad m.m 3.0. «000.0: 09m Sun +2.: 0:3 3 m 5.0 a min .1... m :90 090 88.0.. flan 0m... 0:3 06m 3 ma m4 mad 39.0.. and .93 93 Tu: 3 0.? an R0 $010. 0n.n 0a.: mam min 3 u 2.? a TD: 3.3 m 8.0 3.0 $3.0: and SA dam 0.9. 3 0.300. 33. 3.0 31:6. moé 0n... Tam 0.5m 3 068 0.8- :06 33.0.. 00% 00.: ......R R0: 3 u 0.9». « Rm fin u ~00 nn.0 $8.0. 0m.~ SA ~28 0.? 3 0.2.: 0.3 3.0 9.8.0. Rim m0... 3.? 0.9.. 3 ... .38 on _ em a: _ 3 1830850 . . . El 7 383 NA pen 5 pen u 303 .9182: sea-385.3 its seaweeds 3.8 8338 0888 gagggogg mpg Ii -30- 0.33 0.00.. 00.0 1.00.0: 00.0 00.0 0.00 0.~0 3 0 0.00 a .30 2.. 0 00.0 00.0 . 0000.0. 00.0 00.0 0.00 .30 3 0.300 0.00 0.0.0 0000.0 00.0 00.0 0.00 0.00 3 0 0.00. 0.0 «0.0 0000.0. 00.0 00.0 0.00 0.00 3 u 0.0 0 0.0.. 0.0.. 0. 00.0 00.0 38.0.. 00.0 00.0 0.3 04.0 3 0.0. 0.0 00.0 3000.0. 00.0 00.0 0.3 3.00 3 0 0.00 0.0 00.0 300.0 00.0 00.0 0.00 «.00 3 0 0.3 0 0.30 0.: 0. 00.0 5.0 080.0 00.0 0.0.0 0.3 0.3 3 0.0: 0.00.. 00.0 23.0.. 03.0 00.0 0.00 0.00 3 0 0 0.0 3.0.. 00.0 «08.0 00.~ 00.0 0.00 0.00 3 u 0.0 u 0.0 ...? 0 00.0 ~06 38.0 00.0 00.0 0.00 0.00 3 0.0 3.0 30.0 008.0 00.0 00.0 040 0.00 3 0 ~.0~ 2.9. 00.0 0000.0 2.... 00.: 0.00 0.00 3 u 0.0 u 0%. 0.0 0 00.0 00.0 0000.0 00.: 00.0 0.00 «.00 3 0.00 0.0.. 00.0 2.00.0 00... 00.0 0.30 0.3 3 0 3 5.33500 30: .003 u: _ .00 u: _ .00 0.30930 «0.50 S .50 m an... 0880.— 0am 03 03.803 030.320 .75 3:828 TEE 33:3. 38.30 Ezra an.) 0.00 0.0- 00.0 0030.0 00.3 00.0 0.03 3.00 3 u 3.00 0 0.300 0.00- .0 00.0 00.0 0000.0 00.3 00.3 0.3 0.33 3 0.000 0.00 . 00.0 0000.0 00.0 00.3 0.00 3.03 3 30 0.00 0.0. 33.0 0300.0. 00.0 00.3 0.00 0.03 3 u 0.0. 0 0.00 0.0- 0. 03.0 00.0 0000.0. 00.0 00.3 0.00 0.03 3 0.0 3.0. 3.0 0000.0. 00.0 00.3 0.00 0.03 3 00 0 Q0000 0.00 00.0 0030.0 00.3 00.0 0.33 0.00 40. 0 0.00 0 0.000 0.00. m 00.0 30.0 800.0 00.0 00.0 0.3 0.3 3 0.0 0.0 00.0 0000.0 00.0 00.0 0.30 0.0.0 3 00 0.0 0.0 0.3.0 0330.0. 00.0 00.0 0.03 0.00 3 0 0.00 0 0.000 0.00- 0 03.0 03.0 0000.0. 3.0 00.0 0.00 0.00 3 3.000 0.00 00.0 0000.0. 3.0 00.0 0.00 0.00 .3 00 3.00.0 0.00- 00.0 0000.0. 00.0 00.0 0.00 0.00 3 . 0. 0.30 0 0.30.00 0.00 0 03.0 0.0.0 0000.0. 00.0 00.0 3.30 0.00 3 0.00 0.0- 00.0 0000.0. 00.0 00.0 0.03 0.00 3 00 0 .00 a: .0» u: .0» 000000.700. In: an . 050330 00.50 3 .50 0 58: 2.3.00.0 0am 000 000.8000 000.00.005.00 000.00 ...-03.00 ...-0.0 :0adnom 09080.0 ES Hubs -32- 0..0dduu.u0.0a . mn.>pnyuv 00 an. 00 0000 000:0. « u 000000>00 0000:0000 0.030 0.00- 03.0 0000.0. 00.0 00.0 0.00 0.03 3 m 0.30 0 3.030 0.00. 0 00.0 00.0 0330.0. 00.0 00.3 0.00 0.0.3 3 0.0 0..0 00.0 0000.0. 00.0 03.3 0..00 0.03 3 00 0.000 0.00 30.0 $0.0. 00.0 00.3 0.0.0 .0003 3 0 3.00 0 0.00.0 0..00- 0 03.0 03.0 0000.0. 00.0 00.3 0..00 0.03 3 0..00 0.0 00.0 3000.0- 03.0 00.3 0.00 0.03 3 00 0.0 0.0 00.0 0330.0 00.0.: 00.3 0.00 3.33 400 0 0.0 a 0.00 ..0 0 00.0 00.0 0000.0 00.0 00.0 0.00 0.00 3 0.000 0.00- 00.0 2.00.0 00.0 00.3 0.00 0.00 3 00 0.0 0.0 00.0 000.0.0 03.0 00.3 0.30 0.03 3 m 0.3 u 3.00 0.0- u 8.0 00.0 0000.0 00.0 00.3 0.00 0.03 3 0..00 0..0 00.0 00.3.0 03.3 00.0 0.03 0.30 3 00 0 802.050. . . 20.. . “0M. 0: _ .00 0: _ .00 0.3380 00 £0 3 80 u at: 088.0 00 no.0 bunfluwm 80:0nuhunw0 03.8 ...-08.00 300.0 nflBhflEBE fifl0nflflar -33- identical, the omission of the internal standard line is per- missible. Variations in these conditions are effected by changes in the length of exposure, the amount of sample, the nature of the electrode, the arcing current, plate charac- teristics, and deveIOping procedure. All of these were taken into consideration and carefully regulated. The working curve and data for this method, which are to be found in Ta- bles VI, VII, and VIII and Figure 9, show no great increase in the constancy of results. Ahrens (1950) shows that for small concentrations of K’ ion, the curve of a plot of the logarithm of RIK+ vs. the concentration of K20 changes from an essentially straight line at higher concentrations to a curve at lower concentra- tions. Assuming that the concentrations of Mg" ion in the fossil solutions were low enough to fall within this curved portion of the graph, a working curve was prepared by actu- ally drawing a curved line through the proper points instead of the usual straight line. But no appreciable advantage was observed. This curve is shown in Figure 10 and the Mg” ion concentrations so obtained are recorded in Table IX. It was decided then to investigate the relationships between the relative intensities of Mg 2779.8 and Ca 3006.9 and thus eliminate possible error due to Sr 2931.8 and slight- ly varying conditions of arcing the samples. The Ca and Mg lines of a particular spectrum were, of course, produced un- der identical conditions since the two elements were mixed 1.0 P 0.9 P 0.8 L 0.7 r 0.6 r- Log:RII‘ OJt - 00} p 0.2 '- 001 '- 0.1 Fig. 90 I I 0.5 0.7 1.0 ills” Non-internal standard working curve for plate 1% 1.5 ME VIII lC-Im STANDARD DATA AND PERCENTAGES Mg” OBTAINED -35- Plate Specimen I Trial I Log mug Std. Dev. 11 1 (a) 0.5250 0.55 1111.7 (b) 0.h62h 0.26 0.38 g -31.6 t no.3 1 (c) 0.11771 0.32 -15.8 2 (a) 0.115%} 0.22 -31.3 (b) 0J45hs 0.22 0.32 «1 -31.3 1 52A; g (0) 0.5185 0.51 59.1; 3 (a) 0.5502 0.67 .153 (b) 0.57110 0.75 0.70 i 11.1; t 10.5 at (c) 0.900 0.9+ -s.6 h V (0) 0.6053 0.93 3.3 (b) 0.6021 0.92 0.90 i the t 5.h 6 (c) 0.5555 0.814 -6.6 5 (a) 0.6532 1.16 2.7 (11) 0.6130 0.99 1.13 % -12.h i 11.7 6 (0) 0.6721 1.25 10.6 6 (a) 0.5119 0.19 25.6 (11) 0.14933 0.1:.1 0.39 s 5.1 t 29.9 6 (c) 0.162%; 0.26 -33.3 001 " “3 31nd 3131- o E: ‘ -36... “-002 b L I J I J 0.1 0.5 0.7 1.0 1.5 ‘5 Mg“ Fig. 10. “Curved“ working curve for plate 14 um IX “CURVE“ IORXING CUR" It” AND PERCENTAGES H -37- m1!!!) Avg. I $ Dev. Std. Dev. Plate Specimen I Trial I 1.0; §§§J 1 lg“ n 1 (a) -0.0825 OJ+8 11.6 (1:) 4.0999 0.113 0A3 1 0.0 t 11.6 1 (c) .0425 0.38 -11.6 2 (a) -o.1u92 0.27 -30.8 (‘0) .0.0767 0.19 0.39 1 25.6 a 28.5 1 (c) -0.10h7 0A1 5.1 3 (a) -0.0353 0.62 1.6 (b) -0.0h92 0.58 0.61 1 44.9 ’ t In} 1 (c) -o.oa99 0.6+ 3.3 It (a) -0.0022 0.72 43.3 (b) 0.0580 0.88 0.83 1 6.0 t 11.5 1 (0) 0.0605 0.89 7.2 5 (a) 0.0677 0.91 .2.2 (b) 0.0995 0.99 0.93 1 6.5 * 5-7 1 (0) 0.0593 0.89 44.3 6 (a) 0.0205 0.79 1.3 (0) 0.01110 0.77 0.78 1 .1.3 t 1.6 1 (c) 0.0152 0.77 -1.3 -38- together and arced on the same electrode. Due to the fact that the relative intensities of Mg 2779.8 and Sr 2931.8 were employed to arrive at percentage Mg” ion concentra- tions, it should be permissible to state that the ratios of the relative intensities of Mg 2779.8 to Ca 3006.9 are pro- portional to and depend upon the percentage composition ra- tios of MgII/Ca". Therefore, the percentage-transmissions of the Ca 3006.9 lines were determined and are recorded in Table X along with their relative intensities, which were obtained from the calibration curves. The same table shows that devi- ations do exist in the ratios of RIMg/RICa' Although, in many instances,.two of the three values for each solution were nearly the same, it was considered not feasible to discard the third value and to average the two which were similar since these values might represent the extreme end of the range. Therefore, the three values for each fossil solution were av- eraged together. 66.. Rm... $6 86 .99. o...« .3 “Q6 . .56 R56 .56 8... has «6.. .....« E «6 «$6 no... 36 n6: u.n« 3 .. o6 2m... 8.... $6 .2... m6”. .3 *3; m6 6R6 n66 Sun on... 6;... o6. .5 ..6. «86 RA 8... «6.. o.6« .3 n ma 69.6 36 8... m6m ...ma .3 «a.» a ...m 9.1.6 $1.6 $6 26 ..um m.n« .6 n6- «9.6 «.66 8... min 66. 3 « «6- 936 8...” 2.6 98 «.8 .8 um6 a w6. 2.1.6 2...... R6 36 «.B n.n« 3 «6 «86 .36 86 ...? m6« 3 a .. 3.... .. .. 7. i .. 2.363» .86 a 8.85 «£022 kunflwflm 813%.“? 10m 8536» 3.8 n" Na m and .. ... @313 “Oh mama to ..-: Huang :Hua ..uo- 6.. «86 86 666 «66 6.3 .3 u .... a o... 666 866 86 9.6 64.6 6.3 .5 o..- 9.66 86 666 666 «.5 3 6.6 6.36 $6 86 666 «6. 3 u 6.6 « 66 .66 666 o«6 cm... .6. 6.8 .5 66.. mam... 6.6 on.» 66.. «.8 3 «A 366 666. 36 666 .6. 3 6 a... a 6.... 066 £66 86 666 66.. m6. .3 6.6 366 9.6 9.6 666 6.3 3 6 6...: «$6 666 2.... 64.6 666 .3 u 6... a ..6 6666 2.66 6.6 mm... 666 666 a: .... «36 6.4.6 06... 6.6 ...«n 3 ...... 62.6 E... 26 666 u.«« .3 u n.« a ...« 62.6 8.6 6.... 86 666 6.3 ...: n... 62.6 cm... 666 «...n o6« 3 .. a 3. — 8 9.. — 8 Swat-”u .5. u 0.85 Six}... 0:333 8.33.5.3 3.: 838..» 3.8 3:3... .82.» gun: -01- 66: 636 an... 666 6.6.. 6.5 3 «66 u ..6- «$6 686 2.... on... ...9. u6« 3 o.«. 62.6 86 2.6 666 66... 3 .. 6... 5.6 B6 on... 6.66 o...« 3 u«.« . .6. 6...... 8.6 6«6 66... 666 «.«« 3 ...«u «9.6 ««6 66... 666 6.«« 3 n. m m... «9.6 6.... 666 6;... «6« 3 “.6 a 66.. ..36 ..mm6 86 86 66.. 6..« 3 66.. Rm... .86 86 6...... 66. 3 «. «6.. 6.66 666 666 6.... 6.... 3 m..«« 6.. ..«66 6666 9.6 «.6. «66 6.... 3 6.. 6666 9.6 666. m6. .6. 3 .. 6.... 6«66 $6 666 66... 6.... 3 u ...» u .6 6666 6666 666 86. ...... m6. 3 6.... 69.6 86 86. 6.9. «6. 3 o. 6 83...... 3. _ 8 8. _ 8 9338.. :8 u .9325 83x3...- »atiau. 8.3.35... 3.... lit... 3.... .58.... :88... gun: -42- . «6 «.....o 6&6 664. 066 6...« .8 u ...« « 06 09.6 o«...o 2.6 8.6 6.«6 6.8 .3 6.6.. a... 6... 2.6 $6 a... ... .. I 6.« 6.6 9... 66.. 3.6 6.«« 3 6 ...« a a... 69.6 6.96 6«.6 66... 6.66 ~.«« 3 «.... 6...... 6...... 66.6 ..66 ...« 3 ... «.«a ..26 8.6 66.6 666 6.8 .ofl 6 6.« m 6.6 o«~.o .66.6 66.6 6«.~ 6.«6 6..« .6. ..6- 6666 9.6 666 6.3 6.... 3 6. ...6 62.6 066 8.6 6...6 6..« 3 6 6.6 a 66... 6666 6.66 666 66.6 6.66 66« 3 ... 6n... 9.... 8.6 6.... .66 3 6. 6 83...»... 8 «a _ 8 a: _ 8 6.338... .8 u .955 a}... 63.8.... 82.3.3: ...... 5.82.6 3.... organ 3.9.0.6 Egofla ANALYSIS OF DATA If, in Table II, all the carbonate in specimen #1 were CaCOB, then CaCO3 would comprise 73.4-% by weight of the sam- ple and the brachiOpod would belong to the previously men- tioned calcareous group. Similar calculations show that all the brachiOpods examined have calcareous rather than phos- phatic skeletons. Somewhat lower values for the CaCOB con— tents than those found by Clarke and Wheeler (1917) are due to the fact that not only pure shell material but also sec- ondary silica were pulverized and weighed together. Since the C03: ion is the major anion, MgCOB/CaCOB ratios should have considerable significance. or the two methods used to arrive at a relationship be- tween Ca and Mg, the method of obtaining ratios between the relative intensities of Mg 2779.8 and Ca 3006.9 appears to be the better due to the smaller standard deviations.9 In or- der that these ratios might be more easily visualized, the values for plates 4, 5, and 6 have been graphed as a histo- gram (Figure 11). The first thing one may observe is that the MgCO3/CaCO3 ratios for two specimens of the same genus, species, stratum, 9It was decided to obtain a MgCO /CaCO3 ratio instead of a 03003/Mg003 ratio since a smali change in the Mg603 content would be more significant in the overall ratio. ”lg/310$ 0.9 0.8 0.7 0.6 0.5 Ath- 1 2 3h 5 6 7s 9101112131h15161718 Brachiopod Specimens rig. 11. Blue/RIG; bar graph composite for plates h, 5. and 6 -u5- and collection site are considerably different in several in- stances. This could be the result of the absence of a class- distinct mineralogical selection, evolutionary responses, diagenetic alterations, local environmental variations, the presence of MgCO3 and/or Ca003 along with the secondary sil- ica in the interior cavities imens, or a minor difference two fossils. The presence or absence cal selection could possibly large number of specimens of and age. Adhering sediments, between the valves of the spec- in the geological age of the of a class-distinct mineralogi- be determined by analyzing a the same genus, species, stratum, including any material between the valves, should be separated from the shells previous to these examinations and sediments from the immediate vicinities of their sites of collection should be checked for local en- vironmental variations. If, however, variations were caused by responses to a rapid evolutionary change, it would appear that there existed no class-distinct mineralogical selection for these brachiOpods. The fact that the specimens used for mineralogical-se- lection investigations must be of the same age can not be too greatly emphasized. It must be remembered that the bottom of a particular bed in one locality can represent either the same or a different age than the bottom of the same bed at another locality. This situation is shown in Figure 12, which 38.5.. no 3.8 32533 as: “.83 ...: .6: -u7- is a block diagram of on-lapping sediments with numbered ma- rine organisms. Assuming that there was no relocation of the organisms before their burial, organisms #1 and #2 should be of the same age and organism #h should be younger than organ- ism #3 even though all four organisms are to be found in the same bed. A check on the compositions of the sediments should show indications of environmental variations. If two organisms were located as #6 and #7 in the diagram, where a fresh-water stream enters the sea in the vicinity of #6, it seems not im- probable that the dilution of marine-water constituents would be detectable in the sediments as well as in organism #6 and should result in an analysis which would differ from that of #7 and its associated sediments. If one were to assume that, in the case of the specimens .examined, there were a class-distinct mineralogical selection and no variations due to evolutionary responses or local en- vironmental fluctuations, an interpretation of the MgCOB/CaGOB data might be made on the basis of major environmental and time changes. As stated earlier, many geologists believe that the formations from the Greendale through the Arnheim in southwestern Ohio were deposited by a southern invasion of the sea and those immediately above the.Arnheim by a northern arm of the sea. Since there was little relief in this locali- ty during Ordovician time, such a change in seas could have been accomplished by a gentle warping of the land surface. ..ng- If, with the progression of time, the temperatures Of these seas were rising toward the overall higher temperatures of Silurian time, the associated calcareous marine organisms should reflect this in higher magnesium contents.10 The fos- silized specimens should, therefore, show increases in mag- nesium contents from the Greendale up through and including the Arnheim formations. The specimens in the formations im- mediately above the Arnheim should show the same trend but have slightly lower magnesium concentrations during the first part of this northern sea deposition than the same gen- era and species in the southern sea deposits due to the somewhat cooler waters of the northern sea. The various strata from which the specimens were col- lected are diagrammed in Figure 13 and the fossils are repre- sented by the same reference numbers as in Table I. The dashed lines are time-lines and the solid lines separate different formations. 0n the basis of the data in Figure 11, the specimens are located in the diagram with the idea of increasing magnesium content with time. Therefore, since #1 has more MgCOB than #2, #1 must be younger than #2 and, ac- cording to the law of superposition, be above the time-line for'#2. Specimen ## is younger than #3 and both have greater 10It has been found that, for many calcareous marine skele- tons, the magnesium content increases with the tempera- ture of the organism's environment. -49.. on: .3 o 02 «or as ind-nan flu and 00 and.“ a. 6 Had." 3.vo -50- magnesium contents than #1 or #2. Specimen #5 is younger than #6, etc. If a change in seas occurred, the time of this change might be established by noting where there is a decrease in magnesium contents of fossils of the same genus and species. Specimens #5 and #6 in the Arnheim formation drOp in magnesi- um content to the lower values for #7 and #8 in the Waynes- ville formation. Fossils #17 and #18 in the Whitewater have much less magnesium than #15 and #16 in the Arnheim. This leads to the support of the theory that the deposits above the Arnheim were deposited in a different arm of the sea than those below the Arnheim. However, specimens #9. #10, #11, #12, #13, and #lu seem to vary greatly in magnesium content. On the basis of #13 and #1h, one would believe that no class-distinct mineralogi- cal selection existed for this species or that local varia- tions in their environment had a profound effect. Diagenesis might be a factor of concern, but no alterations were ob- servable megascopically. SUMMARY AND CONCLUSIONS Several facts which were established by means of the preceding investigations are: l) the major and trace elements in all the brachiOpod specimens were similar; 2) the quanti- ties of certain elements varied between different specimens; 3) all the brachiopods examined belonged to the calcareous group; b) the specimens contained less than 1.5 % Mg" by weight; and 5) the ratios of MgCOB/CaCO3 differed between the same species as well as between different genera and species. The analyses of certain specimens seem to support the theory that, in the vicinity of southwestern Ohio, the for- mations from the Greendale through the Arnheim were deposi- ted during a southern invasion of the sea and those immedi- ately above the Arnheim in a northern arm of the sea. Other fossil analyses gave rise to much uncertainty in such an in- terpretation. In order that a solution to the Cincinnati Arch prob- lem may be obtained, investigations should be made along var- ious lines. It should be determined whether or not a class- distinct mineralogical selection exists between the same brachiopod species. Complete removal of all the sediment from the interiors and exteriors of the shells might yield better results. Local environmental changes might be detected -52- in analyses of the sediments associated with the fossils. A consideration of these and other factors should lead to more conclusive results. BIBLIOGRAPHY Ahrens, L. H. (1950) Spectrochemical Analysis; Addison- Wesley Press, Cambridge, Massachusetts, 267 pp. Bowen, V. T., and Sutton, D. (1951) Comparative studies of mineral constituents of marine sponges; Jour. Marine Research, vol. 10, pp. 153-167. Erode, W. R. (19b3) Chemical Spectroscopy; John Wiley and Sons, New York, 77 pp. Chave, Keith E. (1959) Aspects of the biogeochemistry of magnesium; Jour. Geology, vol. 62,p pp 266-283. Clarke, F. W. (1916) The data of geochemistry; U.S. Geo- logical Survey Bull. 616, 821 pp. ' Clarke, F. W., and Wheeler, W. C. (1917) The inorganic con- stituents of marine invertebrates; U.S. Geological Frof. Paper 12h, 62 pp. Epstein, 3., and Lowenstam, H. A. (1953) Temperature-shell- growth relations of recent and interglacial Pleisto- cene shoal-water biota’from Bermuda; Sour. Geology, vol. 61, pp. h2fl-438. Epstein, S., and Lowenstam, H. A. (195h) Paleotemperatures of the Post-Aptian Cretaceous as determined by the ox en isotope method; JOur. Geology, vol. 62, pp. 207-2 253. Goldberg, E. D. (1954) Chemical scavengers of the sea; Jour. Harrison, G. R., Lord, R. 0., and Loofbourow, J. R. (19h8) Practical iSpectroscopy; Prentice-Hall, New York, 655 pp- Kelly, W. A. (195k) Department of Geology and Geography, Michigan State College, personal communication. Krumbein, W. 0., and Garrels, R. M. (1952) Origin and classi- fication of sediments in terms of Eh andng; Jour. Geology, vol. 60. pp. 1-33. I t a o ‘ o 1 . Q I . O ‘ U . . \ . . 0‘ A l a ' I A 0 ‘| 5 . . .- o t e e I. . ' o 0 C “. 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