Deposition and Dolomitization of Upper Knox Carbonate Sediments, Copper Ridge District, East Tennessee

Deposition and dolomitization of Upper Knox carbonate sediments, Copper Ridge district, East Tennessee

HABTE G. CHURNET* ) KULA C. MISRA / Department of Geological Sciences, University of Tennessee, Knoxville, Tennessee 37916 KENNETH R. WALKER )

ABSTRACT tional zoning. These dolostones formed by ment toward the northwest, adjacent to a early diagenetic replacement of limestones very shallow marine environment dotted The upper part of the Cambro-Ordovi- due to dilution of marine pore water by with tidal islands toward the southeast. In cian Knox Group in the fault-bounded fresh water. A mixing-zone environment of the rock record, the former presence of Copper Ridge zinc district, East Tennes- dolomitization is indicated by the following these islands is indicated by thickening of see, consists of interbedded limestones and features of the constituent dolomite crys- fine-grained dolostones and a correspond- dolostones, with very minor sandy and tals: textural zoning with cloudy centers and ing thinning of underlying limestone units. cherty horizons. The nature of allochems clearer rims, concentric luminescent zoning, suggests that the limestones formed in increase of Fe content toward the rims, and INTRODUCTION marine peritidal environments. Other fea- low Na contents and Sr/ Ca ratios untypical tures, such as granular interallochem ce- of the marine environment. The Copper Ridge district, one of the two ments, dolomite inclusions in calcite, low The depositional setting within the area producing zinc districts in eastern Tennes- Na content, and low Sr/Cr ratio, suggest of study was a coastal, tidal flat environ- see, lies in the Copper Creek fault block, stabilization of the limestones in the presence of fresh water. There are two textural varieties of dolostone: (1) fine grained and (2) medium to coarser grained. Fine-grained dolostones, composed of unzoned 0.02- to 0.05-mm dolomite crystals, represent penecontempo- raneous dolomitization of calcareous sediments in upper intertidal to supratidal environments. Evidence for this includes the presence of continuous cryptalgal laminae, mud cracks, birdseyes and oolitic units, the probably former presence of evaporites, and the absence of normal marine fauna. The oolite units may be analogous to modern shoreline occurrences in Laguna Madre and Baffin Bay, Texas. The low Na and Sr con- centrations, as well as the nearly stoichiometric Ca/Mg ratio of the fine-grained dolostones, compared to Holocene supratidal dolomites, are attributed to the formation or neomorphism of the fine-grained dolostones in the presence of fresh water. The medium and coarser grained dolo- Figure 1. Locations of measured sections in the Copper Ridge zinc district, Copper Creek stones consist of 0.1- to 0.8-mm dolomite fault block, eastern Tennessee (after Harris, 11969). 1, River Ridge (this section lies in the crystals that show textural and composi- Clinchport fault block); 2, Thorn; 3, Joe Mill Creek-Rucker Branch/Idol Mine; 4, Tandy- Dalton; 5, Treadway/Flat Gap Mine; 6, Lee Valley; 7, Shiloh. Thrust faults: W, Walden *Present address: Department of Geoscierices, Valley; C, Clinchport; H, Hunter Valley; CC, Copper Creek; S, Saltville; R, Rocky Valley; University of Tennessee, Chattanooga, Tennessee P, Pulaski. Strippled area represents the Mascot-Jefferson City zinc district. 37401.

Geological Society of America Bulletin, v. 93, p. 76-86, 13 figs., 2 tables, January 1982.

Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/93/1/76/3434406/i0016-7606-93-1-76.pdf by guest on 26 September 2021 DEPOSITION AND DOLOMITIZATION OF CARBONATE SEDIMENTS 77

which is bounded by the Copper Creek and RIVER THORN JOE MILL- TREADWAY LEE SHILOH Saltville thrusts. This block comprises a RIDGE HILL RUCKER VALLEY thick sequence of Paleozoic rocks, ranging in age from Cambrian (Rome Formation) to Mississippian (Grainger Formation).

Commercial zinc mineralization is restricted r250M to the Lower Ordovician Kingsport and Mascot Formations, which constitute the upper part of the Cambro-Ordovician Knox 200M Group. These formations crop out along Copper Ridge in a narrow northeast-trend- ing belt for more than 65 km in Tennessee and southwestern Virginia (Hill, 1971). The -I50M Copper Ridge zinc district lies in this belt and includes the Flat Gap and Idol mines as well as a number of zinc prospects (Fig. 1). The Kingsport is composed of medium- •IOOM to coarse-grained dolostones with a varying proportion of limestone and intercalations of fine-grained dolostone. The overlying Mascot is composed primarily of fine- •50M grained dolostones (Harris, 1969). The top of the Mascot is marked by a pronounced unconformity, the post-Knox unconformity, which separates Lower Ordovician rocks from Middle Ordovician rocks. Zinc

mineralization in the district is consistently 19-5 KM 9* KM I6KM • KM 4«KM associated with breccia bodies in the Lower

Ordovician rocks. According to many au- • S S EE3 ÜM m m thors (for example, Wedow and Marie, FINE-GRAINED LIMESTONE MEDIUM AND SANDY CHERT STRCMATO- COVERED 1965; Hoagland and others, 1965; Harris, DOLOSTONE COARSER ZONE 00- LITIC DOLOSTONE OOUTC ZONE 1969; Hill and others, 1971a, 1971b; Hoag- Figure 2. Columnar section of part of the Upper Knox in the Copper Ridge district. The land, 1971), solution of limestone during River Ridge, Joe Mill-Rucker Branch, and Shiloh sections were measured during this the post-Knox erosional interval played a study; data for the other three sections were taken from Harris (1969). The datum used is a major role in the formation of breccia sandstone interval recognizable in most sections and referred to by previous workers as bodies. Harris (1971) suggested that erosion "Chert Matrix Sandstone" (CMS). MO signifies the Middle Ordovician carbonate rocks of the Mascot Dolomite would have provided adequate Mg for dolomitization of that unconformably overlie the Upper Knox Group. the Kingsport. coarser grain size being due to a slow rate of concluded that mineralization (yellow spha- Not much has been published on the dolomitization. Oder and Ricketts (1961) lerite), brecciation, and dolomitization were petrography and composition of the differ- recognized two subtypes of medium- to broadly contemporaneous. In a recent pa- ent types of dolostones; their interrelation- coarse-grained dolostones, one diagenetic per, Hoagland (1976) acknowledged that ships and genesis, therefore, are far from and the other broadly contemporaneous the age relationships of dolomitization have resolved. The fine-grained dolostone occurs with mineralization. On the other hand, not been satisfactorily resolved. He sug- as regionally persistent beds, suggestive Hoagland and others (1965) suggested gested that both early synsedimentary dol- of early sedimentary origin. For regional two phases of epigenetic dolomitization omitization and late dolomitization by dolomitization of the Lower Ordovician by hydrothermal solutions from "unknown hydrothermal ore-bearing solutions prob- carbonate rocks of the eastern United sources and affiliations" later than the ably occurred. States, Laporte (1971) inferred an intertidal post-Knox unconformity—an earlier phase In the present study, we interpret the to supratidal environment, whereas Harris of intense dolomitization with very minor depositional environments of the Kingsport- (1973) argued for a Mg-rich subtidal envi- sphalerite mineralization and a later phase Mascot carbonate sediments and the nature ronment. The medium- to coarse-grained of sphalerite deposition with further dolo- and timing of dolomitization of the Copper dolostone is believed to have formed by mitization. Based on the crosscutting rela- Ridge district. The relevance of these inter- replacement of limestone (Harris, 1969). tionship of the sphalerite-bearing white pretations to zinc mineralization in the dis- However, there is no unanimity of opin- gangue dolomite and the presence of many trict will be discussed in a subsequent paper. ion regarding the timing, environment, or unmineralized breccias, Harris (1971) sug- mechanism of this replacement. According gested that dolomitization was earlier than STUDY AREA to Kendall (1960), the coarse dolostone was mineralization and was produced by a dif- premineralization in age and formed by late ferent solution. However, from a geochemi- The interpretation presented here is based diagenetic replacement of limestone, the cal study of the Flat Gap mine, West (1974) on investigation of three sections (River

Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/93/1/76/3434406/i0016-7606-93-1-76.pdf by guest on 26 September 2021 78 CHURNET AND OTHERS

Ridge, Joe Mill Creek-Rucker Branch, and includes trilobites, gastropods, ostracods, clear, blocky calcite cements as well as the Shiloh), published data on three other mea- brachiopods, pelmatozoans, and sponges. isopachous cement around ooids (Fig. 4) sured sections (Thorn Hill, Treadway, and Most of the allochems have micritic enve- are indicative of a phreatic environment of Lee Valley) compiled by Harris (1969), and lopes, probably caused by microboring formation (Bricker, 1971; Land, 1973; Mey- study of selected samples from the Lee Val- algae and fungi (Perkins and Halsey, 1971). ers, 1974). The dolomite inclusions in some ley section, the Tandy Dalton prospect, and Planar algal-laminae and birdseyes are dis- of the calcite cements are diagnostic of a the Idol Mine. Locations of these sections cernible in some samples. No marine fibrous mixing-zone environment (Folk and Sied- are shown in Figure 1. Broad lithologic or columnar cements (Bricker, 1971; Bat- lecka, 1974). Such dolomite inclusions in variations in each of the six sections and hurst, 1975) were observed. Instead, intra- calcite could have formed by alteration of stratigraphic correlations among them are allochem cements and matrix have been high-Mg calcite cements (Meyers and Loh- presented in Figure 2. All of the sections are neomorphosed to microspar, and interallo- man, 1978), but the sharp contacts between in the Copper Creek fault block except the chem cements are drusy and granular-to- dolomite and calcite in interallochem spaces River Ridge section, which is in the adjacent blocky, low-Mg calcites (Fig. 3) with trace (Fig. 3) suggest that the two minerals pre- Clinchport fault block. At present, the amounts of Fe and Mn. The average of ten cipitated contemporaneously from solutions Upper Knox carbonate rocks on these two electron microprobe analyses of the interal- that were saturated with respect to both cal- adjacent fault blocks are separated by a dis- lochem calcite is as follows (in weight per- cite and dolomite. Similar sharp boundaries tance of 6.2 km. Their separation prior to cent): Ca = 39.79, Mg = 0.18, Fe = 0.05, and between sphalerite and calcite in carbonate- shortening by thrusting was about 13 km, Mn = 0.05. Some of the interallochem cal- hosted zinc deposits have been regarded as based on the palinspastic reconstruction of cite grains are in sharp contact with dolo- indicative of equilibrium coprecipitation Roeder and Witherspoon (1978). The loca- mite and in some cases are poikilotopic with (Anderson, 1975). The dolomite-calcite co- tion of the River Ridge section as shown in dolomite inclusions. precipitation has not been demonstrated Figure 2 and Figure 13 has been adjusted The allochems of the winnowed sedi- experimentally because of kinetic problems accordingly. ments (intraclasts, fossil fragments, ooids) in precipitating dolomite under sedimentary suggest that the limestones formed in shal- conditions (Katz and Matthews, 1977). CARBONATE PETROLOGY low marine environments (intertidal to shal- However, theoretically calculated satura- low subtidal). However, many features of tion curves for mixtures of marine and fresh Textural Classification of Dolostones the limestones indicate that diagenesis oc- waters indicate that a mixture with more curred in the presence of fresh water. The than 40 wt % marine water is saturated with Dolostones of the Upper Knox in the Copper Ridge district can be subdivided TABLE 1. COMPARISON BETWEEN FINE-GRAINED AND into two textural groups; (a) fine-grained MEDIUM AND COARSER GRAINED DOLOSTONES dolostones (mostly 0.02 to 0.05 mm) and (b) medium and coarser grained dolostones Criteria Fine-grained dolostones Medium and coarser grained dolostones (mostly 0.1 to 0.8 mm). The medium and coarser grained dolostones include the me- Grain size Mostly 0.02 to 0.05 mm Mostly 0.1 to 0.8 mm dium, coarse, and very coarsely crystalline Zoning Predominantly unzoned Mostly zoned with cloudy center and groups of Folk (1965). This classification is clear rim; often several concentric luminescent zones detected. Generally Fe useful for interpretation of origin because content increases from core to rim of a the two textural groups have distinctly dif- crystal. ferent characteristics (Table 1). Brecciated Sedimentary features Wavy to planar cryptalgal Algal laminae rarely present dolostones contain a very coarsely crystal- laminae abundant line variety of dolomite (the "white gangue Mudcracks No mudcracks observed; however, pre- dolomite" of some authors), which, often dolomitization fractures are observed with sphalerite, forms the breccia matrix. No ghost fauna Ghost fauna is sometimes observed This very coarse dolomite, although a con- Crystalline fabric Xenotopic* Commonly hypidiotopic* sistent feature of Mississippi Valley-type Generally no inclusions Poikilotopic; high Mg-calcite inclusions sulfide mineralization in many districts in partially dolomitized limestones; also, sometimes blocky calcite in sharp contact (Beales, 1975), is clearly later than the with dolomite cement. formation of the dolostones mentioned Generally uniform grain size Mostly porphyrotopic* above, and so is excluded from the present Vug-fillings Sometimes, an outer lining to Dolomite discussion. chalcedony followed by dolomite Ca/Mg molar ratio Nearly stoichiometric (average Higher and variable compared to ideal Limestones 1.009) ordered dolomite (1.098-2.037) Na and Sr contents Maximum values about 210 ppm Maximum values about 370 ppm Na and The limestones consist of interlaminated Na and about 230 ppm Sr, lower about 235 ppm Sr, lower than expected if biointrapelsparitic grainstones/packstones than expected if the dolomites the dolomites formed from normal marine formed from normal marine water; Sr/Ca ratio equal to half that and biomicritic wackestones (terms after water determined for limestones. Folk, 1959, and Dunham, 1962), with some aggregate grains and occasional ooids. In •Textural terms after Friedman (1965). decreasing order of abundance, the fauna

respect to both calcite and dolomite (Chur- net, 1979; Churnet and Misra, 1978). The granular interallochem cements are also indicative of stabilization of the limestones in the presence of fresh water (Badiozamani and others, 1977). This conclusion is compatible with the trace-element distribution in the limestones (Churnet, 1979; Churnet and Misra, 1981): low Na content (Table 2), low Sr/Ca ratio (average value = 0.00047), and poor correlation between Sr and Fe as Figure 3. Photomicrograph of slightly Figure 4. Photomicrograph of oosparite well as between Sr and Mn. dolomitized limestone from the Kings- from the Kingsport Formation (River Ridge port Formation (River Ridge section) section) showing radial fabric in ooids and Fine-grained Dolostones showing blocky calcite cement (C) in sharp isopachous cement around ooids. Scale bar contact with euhedral dolomite (D). Scale = 0.5 mm. The fine-grained dolostones are com- bar = 1 mm. posed of xenotopic (sensu Friedman, 1965) dolomite crystals that are less than 0.06 mm (generally 0.02 to 0.05 mm) in size. Electron evaporites, (4) absence of normal marine casionally (for example, in the River Ridge microprobe analysis shows that the crystals fauna, (5) oolitic units (now chertified), section), ripple-laminated sandstones and have a nearly stoichiometric Ca:Mg ratio, which may be analogous to modern shore- intraclastic conglomerates occur interbed- with variable Fe contents (1,000 to 1,800 line oolites of Laguna Madre or Baffin Bay, ded with wavy laminated dolostones. The ppm) and trace amounts of Mn (less than Texas, and (6) comparison to Holocene planar to wavy laminations in these rocks 400 ppm). Reddish dolomites such as those analogues. These lines of evidence are resemble the cryptalgal laminites observed near the post-Knox unconformity tend to detailed below. in Holocene peritidal deposits (Shinn and have a higher Fe content (about 23,000 Wavy and planar laminae, often marked others, 1965; Ginsburg and Hardie, 1975; ppm). The dolomite crystals show no de- by alternation of lighter and darker colored Monty, 1976; Golubic, 1976). Similar fea- tectable compositional or cathodolumines- materials, are a conspicuous feature of the tures in ancient carbonate sequences have cent zoning. dolostone (Fig. 5). Often, discontinuous also been ascribed to algal activity in Sedimentary features in the dolostones quartz-rich lenses occur in the lighter col- peritidal environments (Thompson, 1975; include laminae, mudcracks, scour and fill ored laminae. Usually the grain size of the Wanless, 1975; Mazzullo and Friedman, structures, cross-bedding, parallel laminae quartz is about 0.04 mm, but scattered, 1977). of quartz and greenish shales, and size grad- rounded, and coarser (up to 0.6 mm) quartz Harris (1973) noted the presence of mud- ing. Chert nodules and layers, some of them grains occur in some of the beds. Oc- cracks in the dolostones and limestones of preserving oolitic textures, occur in some of the beds and along bedding planes. Birdseyes infilled with coarse-grained dolomite are TABLE 2. TRACE-ELEMENTS CONTENTS OF UPPER KNOX also present in some of the beds. Other CARBONATE ROCKS AND CARBONATE MINERALS observed features include microfaulting, load Limestones Fine-grained dolostones Medium and coarser casts, and bed-aligned stylolites. grained dolostones Harris (1973) proposed that the Upper Knox dolostones formed in a subtidal N max. average N max. average N max. average environment by refluxion of hypersaline solutions. This interpretation was primarily This study (neutron activation analyses)* based on recognition of abundant vertically stacked hemispheroidal stromatolites in the Na 6 155 82 ±40 6 209 176 ± 63 6 365 319 ± 56 Mn 6 384 ± 384 Kingsport, largely replaced by penecontem- 135 73 ±38 6 241 138 ± 88 6 927 Sr 6 281 231 ± 38 6 226 6 n.d. n.d. poraneous chert (Harris, 1969). Such stro- § matolitic occurrences were not confirmed in West, 1974 (atomic absorption analysis)] this study. Moreover, modern analogues Mn 14 684 301 ± 179 5 225 164 ± 55 44 836 412 ± 160 suggest that such stromatolites usually grow Sr 14 247 188 ±142 4 50 38 ± 21 44 234 52 ±43 in intertidal environments (Logan and oth- Zn 14 52 24 ± 13 5 24 13 ± 9 42 605 39 ± 101 Cd 14 12 7 ±2 5 24 15 ± 9 44 55 18 ± 10 ers, 1964). Fe 10 500 277 ± 150 5 1,587 1,382 ± 246 44 3,980 1,956 ± 790 We propose an early diagenetic (penecon- temporaneous), upper intertidal to supra- Note: trace elements contents in ppm. tidal origin for the fine-grained dolostones, N = Number of samples. based on the collective strength of the * = Whole-rock analyses. following lines of evidence: (1) continuous t ~ Analyses of carbonate fractions in the rocks, n.d. = Not detected. cryptalgal laminae, (2) mud cracks and § = Only one other sample had detectable Sr (67 ppm). birdseyes, (3) probably former presence of

Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/93/1/76/3434406/i0016-7606-93-1-76.pdf by guest on 26 September 2021 80 CHURNET AND OTHERS

Figure 5. Wavy laminae in fine-grained Figure 6. Polygonal mudcracks in fine- Figure 7. Nodular vug fills in fine-grained dolostone of the Mascot Formation (Joe grained dolostones of the Mascot Forma- dolostone of the Mascot Formation (Joe Mill Creek-Rucker Branch section). tion (River Ridge section). Scale is given by Mill Creek-Rucker Branch section). The the 25 cent coin (arrowed). vug fill is primarily of coarse-grained, baroque-type dolomite with an outer rind of the Upper Knox, but he argued that they the dolomite vug-fills in some cases with length-slow chalcedony. Scale is given by could have formed in subtidal environments length-slow chalcedony (Folk and Pittman, the 25 cent coin (arrowed). as a result of contraction and expansion of 1971; Siedlecka, 1972); (d) occurrence of shales. The shaly layers in the carbonate brecciated beds (Mazzullo and Friedman, sequence are thin and discontinuous, and 1977), particularly when underlain and ronment of ooid formation (prechertifica- they probably represent stylocumulates. overlain by undisturbed beds; and (e) zona- tion) was more analogous to the modern Moreover, the polygonal shapes of the tion of nodules similar to that described by Baffin Bay or Laguna Madre occurrences cracks in plan view (Fig. 6) and their wedge- Milliken (1979) as indicating replacement of detailed by Land and others (1979), that is a shaped nature (tapering downward) in cross evaporites. Additional but very indirect shore-associated environment of variable section are diagnostic of mudcracks that clues to the possible early presence of gyp- salinity. Fabrics similar to the Knox oolitic resulted from subaerial desiccation. Where sum would include the paleolatitude (20° to cherts could result from caliche origin the mudcracks are associated with shaly 30° south of the equator; Smith and others, (James, 1972), but other features of modern material, the cracks are not infilled by 1973) as well as the presence of two distinct caliches (Dunham, 1969b) were not found. shales. This suggests that the cracks were sizes (decimicron and centimicron) of quartz The alignment of chert nodules and layers infilled before the shaly material was grains. Such bimodal distribution of quartz with general bedding strongly suggests that formed. The presence of birdseyes provides grains suggests deposition by wind and chertification was a synsedimentary or very another indication of subaerial exposure of hence possible aridity of the region (Folk, early diagenetic phenomenon. The fact that some of the beds (Shinn, 1968). 1968). The absence or rarity of preserved allochems (ooids, intraclasts, peloids) are Former nodular vugs in the dolostone gypsum or anhydrite could have been preserved in chert may suggest that this are generally infilled by very coarse grained, caused by periodic flushing with fresh water chertification was very early diagenetic and often ferroan, dolomite crystals that tend to (Shinn and others, 1965). Anhydrite vug- preceded dolomitization, for in areas of have arcuate cleavages and wavy extinction. fills have been reported in some brecciated dolostone adjacent to chert, allochems are Sometimes the vug-fillings also include and sphalerite mineralized zones, for exam- often not preserved. However, chert often length-slow chalcedony. Where the chal- ple, from the Puncheon Camp Creek area occurs as a cement in dolostones. Thus, cedony occurs as an outer rind of the vug- (Hill, 1971) and from the Idol and Flat Gap chertification was broadly contemporane- fill, the nodules stick out on weathered mines (Mantooth and Morris, 1979, per- ous with dolomitization, or there were mul- surfaces (Fig. 7). Some of the nodules are sonal commun.), but such anhydrites might tiple periods of chert formation. Prior to the infilled by what appears to be vadose silt have been precipitated from minera.lizing formation of chert, diagenetic fluids must (Dunham, 1969a). Rarely, some vugs have solutions as suggested by Anderson (1973, have contained silica in solution; in other an earlier lining of drusy cement, probably 1975). words, the solution was alkaline (Peterson of vadose origin, and a later infilling of Some of the chert nodules and layers and von der Borch, 1965; Krauskopf, 1975) sparry dolomite. Sulfate evaporites filling have oolitic textures (Fig. 8), but the and possibly hypersaline (Krauskopf, 1959; similar nodular vugs are known to be asso- absence of current induced sedimentary Eugster, 1973). Thus, the environment un- ciated with dolomites in recent intertidal to structures suggests that these were not der which chert lenses and layers in the fine- supratidal sediments of the Persian Gulf formed in a marine ooid-forming environ- grained dolostones formed was probably (Curtis and others, 1963; Bush, 1973). The ment analogous to the modern Bahamian not normal marine. This is corroborated by possible early presence of gypsum in the example. As is the case with many ancient the rarity of marine fossils in fine-grained Early Ordovician peritidal environments is isolated, thin oolite layers and lenses, the dolostones. inferred from the following indirect lines of association here is with peritidal deposits. The interpretation discussed above is evidence: (a) nodular shapes of vugs (Curtis In addition, these chertified ooids have a based on a comparison of features with and others, 1963); (b) wavy extinction and radial fabric, again similar to many isolated those observed in Holocene dolosuones arcuate cleavages of the coarser grained ancient oolite layers but unlike the tangen- formed in intertidal to supratidal environ- dolomite vug-fills ("baroque dolomite"; tial fabric of modern Bahamian ooids. It is ments. Copper Ridge fine-grained dolo- Folk and Assereto, 1974); (c) association of probable, therefore, that the original envi- stones differ from modern ones in two

Figure 8. Photomicrograph of oolitic Figure 9. Photomicrograph of dolostone, chert in fine-grained dolostone of the Mas- Kingsport Formation (River Ridge section) cot Formation (River Ridge section). Scale showing texturally zone dolomite crystals. bar = 1 mm. Scale bar = 1 mm.

significant aspects, however: (1) the dolo- to 2,000 ppm). In general, the dolomites mite crystals are an order of magnitude have a higher and variable Ca/Mg ratio coarser (0.02 to 0.05 mm) compared to than ideal ordered dolomite; in fifteen elec- Holocene peritidal dolomites (Shinn and tron microprobe determinations, the Ca:Mg Figure 10. A. Electron microprobe tra- others, 1965; Illingand others, 1965); (2) the molar ratio ranges from 1.098 to 2.037. verse across a zoned dolomite crystal (about dolomite has nearly stoichiometric Ca:Mg The medium and coarser grained dolo- 1 mm). Data points correspond to analysis molar ratio (1.009, average of six electron stones were formed by replacement of spots from rim through center to rim of the microprobe analyses) in contrast to the dis- limestones. The best evidence for this inter- crystals. B. Relative intensities and the ordered and nonstoichiometric Holocene pretation lies in the gradational contact approximate locations of cathodolumines- dolomite (mostly greater than 56.2 mole % between coarser grained dolostones and cent zones across the same crystal. CaCo3 in Andros Island; Shinn and others, partially dolomitized limestones. The fol- 1965). These differences can be attributed to lowing petrographic features in the partially aggsadational neomorphism in the presence dolomitized limestones indicate that they of fresh water. Such a diagenetic environ- represent an intermediate product in the alization. Although much of the very coarse, ment is compatible with the low concentra- process of conversion of limestones to sparry dolomite directly associated with tions of Na and Sr in the fine-grained coarser dolostones: (1) the dolomite grain sphalerite seems to have precipitated from dolostones (Table 2). sizes in the partly altered limestones are the mineralizing fluids (Churnet, 1979), the same as those in the medium and coarser formation of coarser bedded dolostones Medium and Coarser Grained Dolostones grained dolostones; (2) dolomite replaces from the same hydrothermal fluids that fossils, peloids, and intraclasts and fills in- produced the sphalerite mineralization is The medium and coarser grained dolo- terallochem pores (Fig. 11); (3) the crystals not supported by field relations. These in- stones consist of crystals generally greater growing across peloids and intraclasts ap- clude the regional extent of the dolostones than 0.06 mm in size but mostly in the range pear cloudy, whereas those growing across (Harris, 1969), the presence of undolo- 0.1 to 0.8 mm. The texture is mostly fossils or pores appear clear; and (4) mitized limestones close to sphalerite min- porphyrotopic (Friedman, 1965), although some dolomite crystals maintain anhedral eralization, and the presence of sphalerite xenotopic, hypidiotopic, and poikilotopic but sharp contacts with low-Mg calcite mineralization in fractures in coarser dolo- fabrics are also common. Other textural cement in interallochem pores (Fig. 12), stone and in breccias containing coarser dolo- features include color-mottling and size- although they sometimes have euhedral stone fragments. Moreover, the textural mottling, the presence of relict peloids and edges in adjacent micritic material. In and chemical characteristics of coarser dolo- fossil fragments, and the occurrence of lens- general, dolomite crystals that grew in stone units adjacent to mineralized zones shaped vugs filled with ferroan dolomite micrite are smaller than those that grew in (for example, at the Shiloh and Joe Mill showing wavy extinction. Often, the dolo- sparite. In the latter case, they sometimes Creek sections) are similar to those in mite crystals are zoned with cloudy centers attain diameters up to 2 mm. Thus, dolomit- unmineralized areas (for example, at the and clearer rims (Fig. 9). Cathodolumines- ization of an interlaminated micrite and River Ridge section). sparite, and / or of a burrowed micrite could cent zoning is also a distinctive feature of We interpret that the medium and coarser result in size-mottled as well as porphyro- these dolomites. In addition, they are char- grained dolostones formed in a marine topic fabric such as in the medium and acterized by compositional zoning, the most water-fresh water mixing zone by early coarser grained dolostones of the present apparent trend being an increase in Fe from diagenetic alteration of limestones that were study. core to rim of individual crystals (Fig. 10). originally deposited in shallow marine en- Mn may or may not show a sympathetic Some previous workers (Hoagland and vironments. The mixing model is based on variation. On the whole, the Mn content is others, 1965; Hill and others, 1971a; West, the areal distribution of the dolostones, very low (often below the detection limit of 1974) have suggested that the dolomitiza- their textural relationships, and the distri- the electron microprobe), but some points tion was produced by hydrothermal fluids bution of trace elements in the carbonate in individual crystals show higher values (up responsible for epigenetic sphalerite miner- rocks (Table 2) and individual dolomite

Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/93/1/76/3434406/i0016-7606-93-1-76.pdf by guest on 26 September 2021 82 CHURNET AND OTHERS

ranged luminescent zones in the dolomite crystals suggests that at least the diffusion of Mn and Fe has not been significant after the formation of the crystals. 4. The dolomite crystals occur in sharp contact with interallochem low-Mg calcite crystals of limestones that are interpreted (in an earlier section) to have been altered diagenetically in the presence of fresh water. Our interpretation of an early diagenetic Figure 11. Photomicrograph of partially origin for these dolostones is based on the dolomitized biopelsparitic packstone from Figure 12. Photomicrograph of partially combined weight of the following consid- the Kingsport Formation (River Ridge sec- dolomitized intrapelsparitic grain- erations. tion). The outline of one brachiopod valve stone, Kingsport Formation (River 1. Some of the dolomite rhombs contain (center) can be discerned even where dolom- Ridge section). Dolomite (D) is clearer inclusions of calcite crystals (up to 9 jum in ite has grown across it. Scale bar = 1 min. across interallochem pore space. Note drusy size) at their centers. Electron microprobe calcite lining around intraclast (1). Scale bar analyses indicate that the inclusions are of = 1 mm. high-Mg calcite (up to 4 wt % Mg). Because high-Mg calcite alters to low-Mg calcite crystals (Fig. 10). The salient points are tuations in the proportion of marine water rather readily (Chave and Schmalz, 1966; summarized below. (Churnet and Misra, 1980). This is thought Gavish and Friedman, 1969), its preserva- 1. The dolostones occur over a large area to be so for the following reasons: (1) the tion may be attributed to an early stage of (Harris, 1969, 1973) and would require an concentration of Mn2+ in marine water dolomitization. However, it is possible that abundant source of magnesium for their (0.002 ppm) is about an order of magnitude the high Mg content of the calcite is an arti- formation. As has been pointed out by Hsu lower than that of Fe2+ (0.01 ppm; Mason, fact of the small size of the inclusions rela- (1963) and Land (1973), solution cannibali- 1966), whereas in fresh water, the reverse is tive to the electron beam diameter (about zation (Goodell and Garman, 1969) or true; that is, the Mn2+ (7 ppm, Wedepohl, 3 fim ) used in the analyses. ground water alone (Hanshaw and others, 1978) is an order of magnitude higher than 2. Cloudy centers in zoned dolomite crys- 1971) could not provide adequate magne- that of Fe2+ (0.67 ppm; Livingston, 1963); tals (Fig. 9) suggest that dolomitization sium for such extensive dolomitization. On (2) about 72% of the Mn2+ in marine water started when the coeval solution was just the other hand, the low Na and Sr contents is tied up in inorganic complexes (Crerar saturated or slightly undersaturated with of the Knox dolostones (Table 2) suggest and Barnes, 1974), whereas much less is respect to calcite, whereas the clearer rims that the dolostones formed from solutions complexed in fresh water (Hem, 1963; suggest that the solution was sufficiently more dilute than hypersaline water (Butler, Berner, 1971), so that the partition coeffi- undersaturated with respect to calcite (Sib- 1973) or even normal marine water (Behrens cient of Mn would be lower in a mixture ley, 1979). Similarly zoned dolomite crystals and Land, 1972). Similar low Na and Sr containing a higher proportion of marine have been used to infer that dolomitization values of the dolomitic facies of the Middle water; (3) as a higher Mg/Ca ratio pro- occurred during and before complete lithifi- Ordovician Mifflin Member in Wisconsin motes faster growth of a dolomite crystal cation of shallow-marine lime muds (Teo- have been interpreted as indicating dolomit- (Land, 1967), crystal layers forming in a doravich, 1958, quoted in Chillingar and ization from mixed solutions (Badiozamani, mixing zone with a higher proportion of others, 1979). The occurrence of several 1973). Other workers (Land, 1973; Veizer marine water would grow relatively faster concentrically arranged luminescent zones and Demovic, 1973; Veizer, 1976; Veizer and incorporate relatively less Mn2+. It implies that easy communication prevailed and others, 1978) have also used low Na and should be cautioned, however, that Mn and between the growing crystal layers and the Sr values to infer diagenetic formation of Fe contributed from dissolution of precur- coeval solution. This would be achieved if dolostones in the presence of fresh water. sor minerals could make the picture more dolomitization occurred before complete complicated. 2. As the partition coefficient of Fe lithification of the precursor lithology. between dolomite and coeval solution is 3. Analysis of trace elements in the 3. In partially dolomitized limestones greater than unity, a dolomite crystal pre- dolostones shows poor correlations between (Fig. 12), some coarser dolomite crystals cipitated in a closed system should show a Fe and Sr, and between Mn and Sr tend to be more transparent, have anhe- decrease in Fe content toward the rim. The (Churnet and Misra, 1981). As fresh water dral edges, and maintain sharp contacts observed opposite trend (an over-all in- contains more Fe and Mn but less Sr than with interallochem low-Mg calcite cement, crease of Fe toward the rim) can be best marine water, the lack of Fe-Sr and Mn-Sr whereas the edges of these crystals are explained by a mixing model in which the correlations supports a mixing model. In- euhedral in adjoining allochems (for ex- proportion of fresh water in the mixture terpretation of trace-element data in the ample, intraclasts), and at these sites the increased as the crystal continued to grow. present context presumes insignificant dif- dolomite crystals appear less transparent. Also, the different Fe/Mn ratios in the suc- fusion of the trace elements over geo- This texture implies that the dolomite cessive growth layers of the same crystal, logic time. This assumption seems to be replaced the allochems but filled the in- observed as cathodoluminescent zones, were reasonable for low-temperature conditions terallochem pores, and it is suggestive probably brought about by crystal growth (Anderson, 1969; Bathurst, 1975). Also, of dolomitization before appreciable lithi- in a mixing environment subjected to flue- preservation of several concentrically ar- fication (Katz, 1971).

4. The medium and coarser grained separated by unbrecciated horizons. Dila- would have served as catchment areas for dolostones are as regional in extent as the tion of Knox dolostone units as postulated fresh water, which when mixed with marine fine-grained dolostones. Also, as discussed by earlier workers has not been observed pore water would have resulted in the alter- in a later section, the two types of dolo- elsewhere in similar settings and is highly ation of limestone to medium and coarse stones show facies relationship. Thus, like unlikely. An alternative explanation pro- dolostones. A major progradational episode the fine-grained dolostones, the formation posed here is that the fine-grained dolostone probably resulted in the advance of a broad of the medium and coarser grained dolo- units are records of islands which expanded tidal-flat environment over the district. stones appears to have been controlled by a during progradational episodes and shrank Thus, the complex facies mosaic shown in regional sedimentary pattern rather than during retrogradational periods. Such ex- the fence diagram could be explained by a epigenetic replacement. pansion and shrinking of islands gave rise to depositional model involving a broad tidal- a thicker sequence of fine-grained dolo- flat environment to the northwest of the DEPOSITIONAL AND stones and thinning of limestones toward River Ridge section (not shown in Figs. 2 DIAGENETIC SETTING the center of the islands. and 13, but inferred from the abundance of The record of the islands is better shown medium and coarser dolostones in the River The fine-grained dolostones of this se- in the bottom half of the fence diagram Ridge section as well as from Walther's quence are interpreted as products of pene- (Fig. 13) where the fine-grained dolostones principle) adjacent to a very shallow marine contemporaneous (very early diagenetic) thin toward the northwest (landward); that environment dotted with islands. dolomitization in supratidal and upper in- is, from the Thorn Hill to the River Ridge A sedimentologic setting that has a broad tertidal environments. Medium and coarser section. A rate of sedimentation exceeding supratidal flat adjacent to a marine envi- grained dolostones resulted from early dia- the rate of basin subsidence probably ronment with scattered islands in a modern genetic dolomitization of intertidal and sub- caused the emergence of the islands. Tidal environment could serve as an analogue tidal limestones. The lateral and vertical and storm activities supplied lime muds and to the Early Ordovician environment. Based relationships of these lithologies, shown in sustained the growth of the islands. These on paleomagnetic data and geometric Figure 13, can provide clues to the envi- lime muds were dolomitized penecontem- considerations, Smith and others (1973) ronments of deposition of the precursor poraneously with their deposition, resulting reconstructed the disposition of continents lime sediments. For the fence diagram of in fine-grained dolostones. The islands throughout the Phanerozoic. During the Figure 13, the datum used was a chert matrix sandstone that is traceable through RR most of the measured sections in the district reported in the compilation by Harris (1969). In those cases where the chert- nçc matrix sandstone was not identified, com- nJH JMCRB parison of lithologies of adjacent sections was used as a basis for correlation. The fence diagram shows thickening to fine-grained dolostone units and a corre- % sponding thinning of limestone units toward the Joe Mill Creek area (JMCRB Section), an area where the producing Idol Mine is located. Such thinning of limestones and thickening of dolostones in mineralized areas observed by previous workers has been attributed to the action of meteoric water that descended from the post-Knox unconformity surface (Wedow and Marie, 25 meters 1965; Wedow, 1971; Harris, 1969, 1971). Scale 10 km These workers believed that as the thickness L of an underlying, more soluble limestone unit decreased by dissolution, the overlying, less soluble, fine-grained dolostone units increased in thickness by collapse and dila- LIMESTONE MEDIUM AND FINE-GRAINED tion. According to Harris (1969), up to COARSE-GRAINED DOLOSTONE about 100 ft of dolostone section could cor- DOLOSTONE respond to thickening by dilation. However, Figure 13. Fence diagram of the Lower Mascot and the Kingsport Formations in the even in the Joe Mill Creek area where sev- Copper Ridge district. The top dashed line corresponds to the Chert Matrix Sandstone (see eral brecciated horizons occur, sufficient Fig. 2). The base of the fence diagram is the contact between the Kingsport and the fracture-filling dolomite to account for such Chepultepec Formations. For reasons of perspective, the location of the River Ridge thickening by dilation were not observed in section is displaced; its palinspastically restored location is 13.5 km north of Thorn Hill. the present study. Morever, the brecciation RR, River Ridge; TH, Thorn Hill; JMCRB, Joe Mill Creek-Rucker Branch; T, Treadway; is restricted to certain horizons, which are LV, Lee Valley; S, Shiloh; CC, location of Copper Creek fault.

Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/93/1/76/3434406/i0016-7606-93-1-76.pdf by guest on 26 September 2021 84 CHURNET AND OTHERS

Cambrian and Early Ordovician, the Valley On the other hand, the regional extent dolomitization in supratidal and upper and Ridge Province of the eastern United and very gentle slope of the epeiric sea intertidal environments; they either formed States was at 20° to 30° S latitude. Pres- model are attractive features. As indicated clue to dilution of hypersaline pore water ently, the Persian Gulf with its islands and in the fence diagram (Fig. 13), a shallow and with fresh water, or were very fine grained coastal sabkha (Illing and others, 1965; broad tidal-flat environment was the depo- dolostones that aggradationally neomor- Purser, 1973; Bathurst, 1975) is within 20° sitional setting in the Copper Ridge district. phosed in the presence of fresh water. to 30° N latitude. Thus, the Persian Gulf An extensively broad intertidal setting prob- Deposition of these carbonate sediments might serve as a guide to the environmental ably was a result of the imperceptible slope occurred in a peritidal environment that setting of the Early Ordovician Copper of the terrain and the greater tidal activity shallowed toward the northwest. The Mas- Ridge district, although the Persian Gulf is associated with such broad shelves. Large cot Formation, composed predominantly of not as extensive. quantities of lime mud can be deposited in fine-grained dolostones, represents a broad Harris (1973) used a variation of the epei- the supratidal zone by normal and storm tidal-flat environment. The Kingsport For- ric sea model of Shaw (1964) and Irwin tides (Ball and others, 1967; Perkins and mation, composed of medium and coarser (1965) to explain the deposition of the Kr.ox Enos, 1968). grained dolostones, limestones, and inter- Group carbonates in eastern Tennessee. He As discussed earlier, chemical and textur- calated fine-grained dolostones, represents suggested that they were deposited in a sub- al data suggest that the medium and a contiguous shallow-marine environment tidal zone of an epi-continental sea. Irwin coarser grained dolostones formed in an envi- dotted with islands. The distribution of the (1965) distinguished the environments of an ronment where normal marine water mixed fine-grained dolostones in the Kingsport epeiric sea as the "X-zone," referring to the with fresh water, whereas the fine-grained was controlled by expansion of the islands environment above wave base and up to the dolostones formed in an environmental set- during progradational episodes and their higher reaches of tidal activity, and the ting of hypersaline solutions, but with fresh shrinking during retrogradational periods. "Z-zone," the portion landward and beyond water lenses. Gebelein (1977) and Gebelein the higher reaches of tidal action. Most of and others (1979) have described a mod- ACKNOWLEDGMENTS the Z-zone was thought to have been ern analogue to tidal-flat dolomites that covered by very shallow water that might be formed from mixing of hypersaline and We thank Helmuth Wedow, Jr., formerly agitated only by wind stress. Restricted fresh water. Based on measurements of of the U.S. Geological Survey, for his help water movement of the shallow water cover salinities, he found that small ridges (up in the field work and valuable discussions. over the extremely broad (tens to hundreds to 2 m above mean tidal level) trapped We also thank D. H. Zenger and K. Badio- of miles wide) Z-zone, coupled with evapo- fresh-water lenses. It is suggested that in zamani for their critical review of an earlier concentration of ions and possible forma- the Copper Ridge depositional environ- version of the manuscript. The paper has tion of Ca-minerals, was thought to have ment, fresh-water lenses were trapped in greatly benefited from careful reviews by caused direct precipitation of dolomite certain parts of the peritidal environment, R. L. Folk and G. R. Heath. The senior (Irwin, 1965). including the islands. Probably, mixing of author's graduate studies at the University However, as Textoris (1969) remarked, normal marine water with fresh water of Tennessee were supported by the African if the Moon was closer to the Earth in resulted in coarser grained dolomite crystals Graduate Fellowship Program administered the early Paleozoic, greater tidal activity (Land, 1973), whereas mixing of hypersa- by the African-American Institute, New should have prevailed in the sea at that line water and fresh water resulted in fine- York. The Professors Honor Fund of the time. Even when uniformitarian concepts grained dolomite crystals. Alternatively, University of Tennessee Department of are applied, ancient epeiric seas should very fine grained dolostones may have Geological Sciences provided some funds have been tide-dominated, because broad formed under hypersaline conditions sim- toward preparation and publication costs. continental shelves of modern shallow seas ilar to those in Holocene peritidal environ- (such as the East China and Yellow Seas, ments and then aggraded to fine-grained REFERENCES CITED the Arafura Sea, the Java Sea, and Hudson dolostones in the presence of fresh water. Bay) are associated with tides of high ampli- tude, greatest tidal ranges, and greatest tidal Anderson, G. M., 1973, The hydrothermal trans- CONCLUSIONS port and deposition of galena and sphalerite current velocities (Klein and Ryer, 1978). near 100° C: Economic Geology, v. 68, The locations of these shallow seas may not The Lower Ordovician Upper Knox rocks p. 480-492. be comparable to the latitude of the Valley (Kingsport and Mascot Formations) of the 1975, Precipitation of Mississippi Valley- and Ridge Province in the Early Ordovician type ores: Economic Geology, v. 70, Copper Ridge district consist predominant- p. 937-942. epeiric seas; nonetheless it appears that a ly of limestones, fine-grained dolostones, Anderson, T. F., 1969, Self-diffusion of carbon shallow water cover on a broad shelf (such and medium and coarser grained dolo- and oxygen in calcite by isotope exchange as the Z-zone of Irwin, 1965) could not be stones. The limestones were deposited in with carbon dioxide: Journal of Geophysical tideless. In addition, the Knox dolostones intertidal to shallow subtidal environments Research, v. 74, p. 3918-3932. contain features (for example, mudcracks Badiozamani, K., 1973, The dorag dolomitiza- and were neomorphosed in the presence of tion model-application to the Middle Ordo- and algal laminations) analogous to those in fresh water. The medium and coarser vician of Wisconsin: Journal of Sedimentary modern supratidal lime muds. Thus, the grained dolostones resulted from eariy dia- Petrology, v. 43, p. 965-984. dolomite must have originated as a postdep- genetic dolomitization of the limestones Badiozamani, K., Mackenzie, F. T., and Thor- stenson, D. C., 1977, Experimental carbo- ositional replacement to these muds and due to mixing of fresh and normal marine not as a direct precipitate as envisioned in nate cementation: Salinity, temperature and water. The fine-grained dolostones repre- vadose-phreatic effects: Journal of Sedimen- Irwin's model. sent products of penecontempora.neous tary Petrology, v. 47, p. 529-542.

Ball, M. M„ Shinn, E. A., and Stockman, K. W„ ed., Depositional environments in carbonate ogists-Society of Economic Paleontologists 1967, The geologic effects of hurricane rocks: Society of Economic Paleontologists and Mineralogists Abstract with Programs, Donna in South Florida: Journal of Geol- and Mineralogists Special Publication, v. 14, v. 6, p. 93. ogy, v. 75, p. 583-597. p. 139-181. Ginsburg, R. N„ and Hardie, L. A., 1975, Tidal Bathurst, R.G.C., 1975, Carbonate sedimenta- 1969b, Vadose pisolite in the Captain Reef and storm deposits, northwestern Andros tion and their diagenesis (2nd ed.): New (Permian), New Mexico and Texas, in Island, in Ginsburg, R. N., ed., Tidal depos- York, Elsevier, 658 p. Friedman, G. M., ed., Depositional envi- its: New York, Springer-Verlag, p. 114-126. Beales, F. W., 1975, Precipitation mechanisms ronments in carbonate rocks: Society of Golubic, S., 1976, Organisms that build stromat- for Mississippi Valley-type ore deposits: Economic Paleontologists and Mineralogists olites, in Walter, M. R., ed., Stromatolites: Economic Geology, v. 70, p. 943-948. Special Publication, v. 14, p. 182-191. New York, Elsevier, p. 113-126. Berner, R. A., 1971, Principles of chemical sedi- Eugster, H. P., and 1-Ming, C., 1973, The deposi- Goodell, H. G„ and Garmon, R. K., 1969, Car- mentology: New York, McGraw-Hill, 120 p. tional environment of Precambrian banded bonate geochemistry of Superior deep test Brand, U„ and Veizer, J., 1980, Chemical iron-formations of the world: Economic well, Andros Island, Bahamas: American diagenesis of a muhicomponent carbonate Geology, v. 68, p. 1144-1168. Association of Petroleum Geologists Bul- system—I: Trace elements: Journal of Sed- Folk, R. L., 1959, Practical pétrographie classifi- letin, v. 55, p. 513-536. imentary Petrology, v. 50, p. 1219-1236. cation of limestones: American Association Harris, L. D., 1969, Kingsport Formation and Bricker, O. P. (ed.), 1971, Carbonate cements, of Petroleum Geologists Bulletin, v. 43, p. Mascot Dolomite (Lower Ordovician) of John Hopkins University Studies in Geol- 1-38. East Tennessee: Tennessee Division of Geol- ogy, No. 19: Baltimore, Johns Hopkins 1965, Some aspects of recrystallization in ogy Report of Investigation, 23, p. 139. Press, 376 p. ancient limestones, in Pray, L. C., and 1971, A Lower Paleozoic paleoaquifer—The Bush, P., 1973, Some aspects of the diagenetic Murray, R. C., eds., Dolomitization and Kingsport Formation and Mascot Dolomite history of the sabkna in Abu Dhabi, Persian limestone diagenesis: Society of Economic of Tennessee and southwest Virginia: Eco- Gulf, in Purser, B. H„ ed., The Persian Gulf: Paleontologists and Mineralogists Special nomic Geology, v. 66, p. 735-743. New York, Springer-Verlag, p. 395-407. Publication, v. 13, p. 14-48. 1973, Dolomitization model for Upper Butler, G. P., 1973, Stronium geochemistry of 1968, Bimodal supermature sandstones: Cambrian and Lower Ordovician carbonate modern and ancient calcium sulfate miner- Produce of the desert floor: International rocks in the eastern United States: U.S. Geo- als, in Purser, B. H., ed., The Persian Gulf: Geological Congress, 23rd, Proceedings, logical Survey Journal of Research, v. 1, New York, Springer-Verlag, p. 423-452. Section 8, p. 9-32. p. 63-78. Chave, K. E., and Schmalz, R. F., 1966, Folk, R. L., and Assereto, R., 1974, Giant arago- Hem, J. D., 1963, Chemistry of manganese Carbonate-sea water reaction: Geochimica nite rays and baroque white dolomite in in natural water: U.S. Geological Survey et Cosmochimica Acta, v. 30, p. 1037-1048. tepee-fillings, Triassic of Lombardy, Italy: Water-Supply Paper 1667-A, 64 p. Chillingar, G. V., Zenger, D. H„ Bissell, H. J., American Association of Petroleum Ge- Hill, W. T., 1971, The geology, applied geochem- and Wolf, K. H., 1979, Dolomites and ologists Abstracts with Programs, v. 1, istry, and drilling results in the Puncheon dolomitization, in Larsen, G., ed., Diagene- p. 34-35. Camp Creek area, Grainger County, Ten- sis in sediments and sedimentary rocks: Folk, R. L., and Land, L. S„ 1975, Mg/Ca ratio nessee [Ph.D. dissert.]: Knoxville, Tennes- Amsterdam, Elsevier, p. 423-536. and salinity: Two controls over crystalliza- see, University of Tennessee, 106 p. Churnet, H. G., 1979, The relationship between tion of dolomite: American Association Hill, W. T„ McCormick, J. E„ and Wedow, H., dolomitization and sphalerite mineralization of Petroleum Geologists Bulletin, v. 59, Jr., 1971a, Problems on the origin of ore in the Lower Ordovician Upper Knox car- p. 60-68. deposits in the Lower Ordovician formations bonate rocks of the Copper Ridge district, Folk, R. L., and Pittman, J. S„ 1971, Length- of East Tennessee: Economic Geology, v. 66, East Tennessee [Ph.D. dissert.]: Knoxville, slow chalcedony: A new testament for van- p. 799-804. Tennessee, University of Tennessee, 237 p. ished evaporites: Journal of Sedimentary Hill, W. T., Morris, R. G., and Hagegorge, Churnet, H. G., and Misra, K. C., 1978, Implica- Petrology, v. 41, p. 1045-1058. C. G., 1971b, Ore controls and related tions of the sedimentary and diagenetic Folk, R. L„ and Siedlecka, A., 1974, The "schi- sedimentary features at the Flat Gap Mine, fabrics in the Lower Ordovician Upper zohaline" environment: Its sedimentary and Treadway, Tennessee: Economic Geology, v. Knox dolostones at River Ridge, East Ten- diagenetic fabrics as exemplified by late 66, p. 748-756. nessee: Geological Society of America Ab- Paleozoic rocks of Bear Island, Svalbard: Hoagland, A. D., 1971, Appalachian strata- stracts with Programs, v. 11, p. 105. Sedimentary Geology, v. 11, p. 1-15. bound deposits: Their essential features, 1980, Zoning in dolomites as indicator of a Friedman, G. M., 1965, Terminology of crystalli- genesis and exploration problem: Economic diagenetic environment involving mixing of zation textures and fabrics in sedimentary Geology, v. 66, p. 805-810. fresh and saline water: Geological Society of rocks: Journal of Sedimentary Petrology, 1976, Appalachian zinc-lead deposits in America Abstracts with Programs, v. 12, v. 35, p. 643-655. Wolf, K. H., ed., Handbook of strata-bound p. 173-174. 1969, Trace elements as possible environ- and stratiform ore deposits, Volume 6: New 1981, Genetic implications of the trace ele- mental indicators in carbonate sediments, in York, Elsevier, p. 495-534. ment distribution pattern in the Upper Knox Friedman, G. M., ed., Depositional envi- Hoagland, A. D., Hill, W. T., and Fulweiler, R. carbonate rocks, Copper Ridge district, East ronments in carbonate rocks: Society of Eco- E., 1965, Genesis of the Ordovician zinc Tennessee: Sedimentary Geology, v. 30, nomic Paleontologists and Mineralogists deposits in East Tennessee: Economic Geol- p. 173-194. Special Publication, v. 14, p. 193-198. ogy, v. 60, p. 693-714. Crerar, D. A., and Barnes, H. L., 1974, De- Gavish, E., and Friedman, G. M., 1969, Progres- Hsu, K. J., 1963, Solubility of dolomite and position of deep-sea manganese nodules: sive diagenesis in Quaternary to Late Ter- composition of Florida ground waters: Geochimica et Cosmochimica Acta, v. 38, tiary carbonate sediments: Sequence and Journal of Hydrology, v. 1, p. 288-310. p. 279-300. time scale: Journal of Sedimentary Petrol- Illing, L. V., Wells A. J., and Taylor, Curtis, R., Evans, G., Kinsman, D.J. J., and ogy, v. 39, p. 980-1006. J.C.M., 1965, Penecontemporary dolomite Sherman, D. J., 1963, Association of dolo- Gebelein, C. D., 1977, Mixing-zone dolomiti- in the Persian Gulf, in Pray, L. C., and mite and anhydrite in recent sediments of the zation of Holocene tidal-flat sediments, Murray, R. C., eds., Dolomitization and Persian Gulf: Nature, v. 197, p. 679-680. southwest Andros Island, Bahamas [abs.]: limestone diagenesis: Society of Economic Durham, R. J., 1962, Classification of carbonate American Association of Petroleum Geolo- Paleontologists and Mineralogists Special rocks according to depositional texture, in gists Bulletin, v. 61, p. 787-788. Publication, v. 13, p. 89-111. Ham, W. E., ed., Classification of carbonate Gebelein, C. D., Randolph, P. S„ Hoffman, Irwin, M. L., 1965, General theory of epeiric rocks: Tulsa, Oklahoma, American Associa- E. J., Garrett, P., and Queen, J. M., 1979, clear water sedimentation: American Asso- tion of Petroleum Geologists, p. 108-121. Mixing zone dolomite in tidal flat sediments ciation of Petroleum Geologists Bulletin, 1969a, Early vadose silt in Townsend Mound of central West Andros Island, Bahamas: v. 49, p. 445-459. (reef), New Mexico, in Friedman, G. M., American Association of Petroleum Geol- James, N. P., 1972, Holocene calcareous crust

Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/93/1/76/3434406/i0016-7606-93-1-76.pdf by guest on 26 September 2021 86 CHURNET AND OTHERS

(caliche) profiles: Criteria for subaerial ex- tory of former evaporite nodules from N. D., ed., Organisms and continents posure: Journal of Sedimentary Petrology, southern Kentucky and northern Tennessee: through time: Special Papers in Paleontol- v. 42, p. 817-836. Journal of Sedimentary Petrology, v. 49, ogy, Paleontological Association of London, Katz, A., 1971, Zoned dolomite crystals: Journal p. 245-256. v. 12, p. 1-42. of Geology, v. 47, p. 38-51. Monty, C.L.V., 1976, The origin and devel- Textoris, D. A., 1969, Supratidal origin of Katz, A., and Mathews, A., 1977, The dol- opment of cryptalgal fabrics, in Walter, M. Appalachian Basin dolostone: Geological omitization of CaC03: An experimental R., ed., Stromatolites: New York, Elsevier, Society of America Abstracts for 1968, Spe- study at 252-295° C: Geochimica et Cos- p. 196-249. cial paper No. 121, p. 470-471. mochimica Acta, v. 41, p. 297-308. Kendall, Oder, C.R.L., and Ricketts, J. E., 1961, Thompson, A. M., 1975, Carbonate coast envir- D. L., 1960, Ore deposits and sedimentary Geology of the Mascot-Jefferson City zinc onments in Ordovician shoaling-upward features, Jefferson City mine, Tennessee: district, Tennessee: Tennessee Division of sequences, southern Appalachians, in Gins- Economic Geology, v. 55, p. 985-1003. Geology Report of Investigation 12, 29 p. burg, R. N., ed., Tidal deposits: New York, Klein, G. de V., and Ryer, T. A., 1978, Tidal Perkins, R. D., and Enos, P., 1968, Springer-Verlag, p. 397-405. circulation patterns in Precambrian, Paleo- Hurricane Betsy in the Florida-Bahama Veizer J., 1976, Diagenesis of pre-Quaternary zoic, and Cretaceous epeiric and mioclinal area—geologic effects and comparison with carbonates as indicated by tracer studies: shelf sea: Geological Society of America hurricane Donna: Journal of Geology, v. 76, Journal of Sedimentary Petrology, v. 47, p. Bulletin, v. 89, p. 1050-1058. p. 710-717. 565-581. Krauskopf, K. B., 1959, The geochemistry of Perkins, R. D„ and Halsey, S. D„ 1971, Veizer, J., and Demovic, R., 1973, Environ- silica in sedimentary environments, in Ire- Geologic significance of microboring fungi mental and climatic controlled fractionation land, H. A., ed., Silica in sediments: Society and algae in Carolina shell sediments: Jour- of elements in the Mesozoic carbonate of Economic Paleontologists and Mineral- nal of Sedimentary Petrology, v. 41, p. sequences of the western Carpathians: Jour- ogists, v. 9, p. 4-19. 843-853. nal of Sedimentary petrology, v. 43, 1975, Introduction to geochemistry: Peterson, M.N.A., and Von der Borch, C. p. 258-271. New York, McGraw-Hill, 617 p. D., 1965, Chert: Modern inorganic deposi- Veizer, J., Lemieux, J., Jones, B., Gibling, M. R., Land, L. S., 1967, Diagenesis of skeletal tion in a carbonate precipitating locality: and Savelle, J., 1978, Paleosalinity and carbonates: Journal of Sedimentary Petrol- Science, v. 149, p. 1501-1503. dolomitization of Lower Paleozoic carbo- ogy, v. 37, p. 914-930. Purser, B. H., 1973, Sedimentation around nate sequences, Somerset and Prince of 1973, Contemporaneous dolomitization bathymetric highi; in the Southern Persian Wales Islands, Arctic Canada: Canadian of middle Pleistocene reefs by meteoric Gulf, in Purser, B. H., ed., The Persian Gulf: Journal of Earth Sciences, v. 15, water, North Jamaica: Bulletin of Marine New York, Springer-Verlag, p. 157-178. p. 144-1461. Science, v. 23, p. 64-92. Roeder, D., Gilbert, D. E„ and Withers- Wanless, H. R„ 1975, Carbonate tidal flats of the Land, L. S., Behrens, E. W., and Frishman, poon, W. D., 1978, Evolution and macros- Grand Canyon Cambrian in Ginsburg, R. S. A., 1979, The ooids of Baffin Bay, Texas: copic structure of Valley and Ridge thrust N., ed., Tidal deposits: New York, Springer- Journal of Sedimentary Petrology, v. 49, belt, Tennessee and Virginia: University of Verlag, p. 250-271. p. 1269-1278. Tennessee Studies in Geology 2, Knoxville, Wedepohl, K. H., 1978, Manganese, in Wede- Laporte, L. F., 1971, Paleozoic carbonate 25 p. pohl, K. H., ed., Handbook of geochemistry, facies of the central Appalachian shelf: Roeder, D., and Witherspoon, W. D„ 1978, Part II—3: Berlin, Springer-Verlag, Journal of Sedimentary Petrology, v. 41, Palinspastic map of East Tennessee: Ameri- p. 25B-250. p. 724-740. can Journal of Science, v. 278, p. 543-550. Wedow, H., Jr., 1971, Model of mineralized Logan, B. W., Rezak, R., and Ginsburg, Shaw, A. B., 1964, Time in stratigraphy: New solution-collapse structures from drilling R. N., 1964, Classification and environmen- York, McGraw Hill, 365 p. statistics: economic Geology, v. 66, tal significance of algal stromatolites: Jour- Shinn, E. A., 1968, Practical significance of birds- p. 770-776. nal of Geology, v. 72, p. 68-83. eye structures in carbonate rocks: Journal Wedow, H., Jr., and Marie, J. R„ 1965, Correla- Mason, B., 1966, Principles of geochemistry of Sedimentary Petrology, v. 38, p. 215-223. tion of zinc abundance with stratigraphic (3rd ed.): New York, John Wiley, 329 p. Shinn, E. A., Ginsburg, R. N., and Lloyd, R. thickness variations is the Kingsport Forma- Mazzullo, S. J., and Friedman, G. M., 1977, M., 1965, Recent supratidal dolomite from tion, west New Market area, Mascot- Competitive algal colonization of peritidal Andros Island, Bahamas, in Pray, L. D., and Jefferson City mining district, Tennessee: flats in a schizohaline environment: The Murray R. C., eds., Dolomitization and U.S. Geological Survey Professional paper Lower Ordovician of New York: Journal of limestone diagenesis: Society of Economic 252-B, p. B17-B22. Sedimentary Petrology, v. 47, p. 398-410. Paleontologists and Mineralogists Special West, J., 1974, Trace element geochemistry of the Meyers, W. J., 1974, Carbonate cement Publication, v. 13, p. 112-123. coarse crystalline ore-breccia dolomite in the stratigraphy of the Lake Valley Formation Sibley, D. R., 1979, Dolomitization of Plio- Flat Gap mine, Treadway, Tennessee [Ph.D. (Mississippian), Sacramento Mountains, Pleistocene carbonate sediments, Bonaire, dissert.]: Knoxville, Tennessee, University of New Mexico: Journal of Sedimentary Pet- Netherlands Antilles: American Association Tennessee, 91 p. rology, v. 44, p. 837-861. of Petroleum Geologists Abstracts with Pro- Meyers, W. J., and Lohman, K. C., 1978, grams, v. 6, p. 164. Microdolomite-rich syntaxial cements: Pro- Siedlecka, A., 1972. Length-slow chalcedony posed meteoric-marine mixing-zone phreatic and relicts of sulphates: Evidences of evapo- cements from Mississippian limestones, New ritic environments in the upper Carbonifer- Mexico: Journal of Sedimentary Petrology, ous and Permian beds of Bear Island, MANUSCRIPT RECEIVED BY THE SOCIETY v. 48, p. 475-488. Svalbard: Journal of Sedimentary Petrol- JANUARY 30, 1981 Milliken, K. L., 1979, The silicified evaporite ogy, v. 42, p. 812-816. REVISED MANUSCRIPT RECEIVED syndrome—two aspects of silicification his- Smith, G. A., Briden, J. C., and Frewry, G. E., APRIL 27, 1981 1973, Phanerozoic world maps, in Hughes, MANUSCRIPT ACCEPTED MAY 1, 1981

Printed in U.S.A.

Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/93/1/76/3434406/i0016-7606-93-1-76.pdf by guest on 26 September 2021