|Original published in D.F. Merriam, ed., 1964, Symposium on cyclic sedimentation: Kansas Geological Survey, Bulletin 169, pp. 43-56|
Brigham Young University, Provo, Utah
Sediments of the Ely Group (Pennsylvanian) include lower Ely Limestone (= Moleen), upper Ely Limestone (= Tomera), and Hogan Formation. This group exhibits rhythmic and cyclic arrangement of skeletal to bioclastic, calcarenitic, micritic, and detrital limestones. The various patterns occur in sequences aggregating 1,500 to 2,000 feet in thickness.
Arcturus Group includes Riepe Spring Limestone (below), Riepetown Formation, Pequop Formation, and Loray Formation. Ferguson Mountain Formation is found in northeastern Nevada and northwestern Utah, and is the lateral equivalent of the Riepe Spring and Riepetown in the group; it is Wolfcampian age. Pequop and Loray are of Leonardian age. Total thickness of the Arcturus Group is approximately 6,000 feet, consisting of interbedded reefal, skeletal, bioclastic, lithoclastic, detrital, and micritic limestones, shale and siltstone, sandstone, evaporitic dolomite, claystone, gypsum, and collapse breccia. Units in the group are cyclically arranged in some areas, and elsewhere are recurrent, rhythmic, or other patterns, such as triads and tetrads.
Marine strata of Guadalupian age in western Utah and eastern Nevada include, in ascending order, Kaibab Limestone, Plympton Formation, Indian Canyon Formation, and Gerster Formation; these comprise the Park City Group. The entire succession is one of cyclically arranged to rhythmically controlled triads and tetrads of skeletal, detrital, and micritic limestones, arenaceous criquinites, dolomite, and dolomitic sandstone. Garden Valley Formation (Wolfcampian to Guadalupian age) occurs in a north-south area proximal to the Sonoma orogenic belt in Nevada, and contains rhythms to cycles of coarse sediments and various limestones.
The interpretation is advanced that patterns of sedimentation of the Pennsylvanian and Permian marine and transitional rocks in the area under consideration were mainly controlled by diastrophism within and adjacent to the depocenters. Less emphasis is placed on the hypothesis of glacial control, though this likely influenced eustatic sea level changes in Permian time and this in turn was reflected in sedimentary patterns of the Loray Formation (transgression and regression), and of the Gerster Formation. Evidence favors the interpretation based on periodicity of orogenic and epeirogenic pulsations of marginal and intra-basin landmasses, and within subsiding basins, troughs, shelves, banks, and evaporite pans, and related depositional areas. Marine oscillations and concomitant transgressive-regressive sedimentation across these depocenters established patterns of carbonate and related sedimentation. Rhythmic activity of the various orgenic belts and highlands provided detritus and otherwise initiated and controlled patterned sedimentation; certainly the Garden Valley Formation evinces this relationship.
Park City Group disconformably overlies the Arcturus Group, and consists of the Kaibab Limestone (below), Plympton Formation, Indian Canyon Formation, and Gerster Formation (Table 1). A significant disconformity separates the Triassic Thaynes Formation from the Gerster, and a substantial hiatus is indicated by absence of Ochoan-age rocks and lower Early Triassic sediments.
Table 1--Stratigraphic nomenclature of part of eastern Nevada and western Utah.
|Ls, Sh, SIst, interbed; brick red, red bwn, maroon; sandy; thin bed.|
|Ls, tan, pnk gy, med gy; micritic to cse text, skeletal and lithoclastic to bioclastic; cherty in part; thin to thk bed.|
|Guadalupian||Park City||Indian Canyon||200
|Dol, Slst, Ss, Ls, interbed; pnk gy, gy bwn, red gy, bwn gy; pelletoid to oopelletoid; micrItic to lithoclastic; thin to med bed.|
|Dol, white to It gy, pnk gy, med gy; micritic to cse xln; irregularly cherty (bwn); contains fossil relics; med to thk bed.|
|Ls, It gy, pnk gy, tan to med gy; micritic to cse xln, encrinal to skeletal; thk bed to mass; bwn chert bands and blebs; in part dolomic.|
|Slst, Sh, Dol, Ls, Gypsum, and collapse breccia; bwn, rea bwn, bwn gy, maroon, gy bwn; fissile to thk bed; hydrocar odor when broken.|
|Pequop Upper Member||700
|Ls, argill to micritic and skel; oopelletoid, algal, and bryalgal; med gy to bwn gy; thIn to thk bed; fusuhnal to reefal.|
|Pequop Summit Springs Member||1,000
|Ls, Dol, Gypsum, collapse breccia; white, It gy, med gy, red bwn and red gy; micritic to skeletal, abd facies changes; thin to thk bed.|
|Pequop Lower Member||1,000
|Ls, tan, pnk gy, It olv gy; lithoclastic, micritic, skeletal; encrinal and fusulinal, algal and coralgal; thin to thk bed.|
|Ss, Slst, Ls, in part dol, tan, yel tan, It red gy, mea gy; argill to fine text; lithoclastic, micritic, skeletal; thin to med bed.|
|Ls, med gy, med olv gy, pale pnk gy; micritic to skeletal, reefal, algal, bryalgal, coralgal, fusulinal, encrinal; med to thk bed to massive.|
|Slst, Ls, v. fine gd Ss, interbed; med gy, yel tan, red gy, lav gy to It maroon; mIcritic, detrital, skeletal; thin to med bed, cherty.|
( = Upper EIy Ls.)
|Ls, micritic, detrital, skeletal; med It gy, It pnk gy, It olv gy; encrinal, coralline, fusulinal; med to thk bed; bwn chert present.|
( = Lower Ely Ls.)
|Ls, It olv gy, It tan gy, It bwn gy, med gy; micritic, skeletal, encrinal, coralgal; thin to thk bed; abd. bwn weathering chert bands.|
( = "Jensen" Member.
of Chainman Fm.)
|Ls, Calcarenite, Ss., Slst, Sh; red, red bwn, med bwn, dk bwn, red gy, blk; encrinal, lithoclastic and bioclastic; fissile to med bed.|
Ely Limestone accumulated in marine realms of the Ely Basin, an integral part of the Cordilleran miogeosyncline. The lower member (= Moleen) consists of interbedded and intercalated, as well as recurrent micritic, skeletal, lithoclastic and bioclastic suites of carbonates and related sedimentary rocks. Dott (1958, p. 3-14) discussed the cyclic patterns developed in the mechanically deposited limestones of the Ely Group in northeastern Nevada, stating: "One is immediately impressed with the cyclic or rhythmic appearance of the Pennsylvanian throughout the Great Basin." Brill (1963, p. 314-315) stated: "Cyclic sedimentation is more common in the Morrowan than in the other epochs. Cycles consist of three members. In the Burbank Hills, Arrow Canyon, and Gass Peak sections, the basal member is nonresistant shale, siltstone or very fine-grained sandstone, the middle member argillaceous limestone with small chert nodules, and the upper member crystalline or oolitic limestone with or without chert nodules. In the Confusion Range, cycles have a basal nonresistant silty or shale layer overlain by gray argillaceous limestone, with the upper member a cliff-forming sandy limestone." Mollazal (1961, p. 3-35) made a rather exhaustive study of the petrology and petrography of the Ely Limestone in western Utah, east-central and northeastern Nevada, and his descriptions and illustrations firmly establish the cyclic pattern. These workers all emphasized the truly cyclic nature of many of the units which comprise the Ely and correlative formations. The present report merely adds emphasis by pointing to the fact that carbonates and related sediments of the lower and upper Ely Limestone display marked and definitive patterns of sedimentation (Fig. 1).
Figure 1--Cyclic patterns in Ely Limestone of Burbank Hills-Confusion Range, western Utah.
Hose and Repenning (1959, p. 2170-2174) emphasized the bioclastic and lithic nature which characterizes the Ely in the Confusion Range of western Utah. An illustration of this pattern in outcrops in the Burbank Hills directly south of the Confusion Range was presented by Bissell (1962b. Pl. 2, Fig. 1). Further details are provided in Figure 1 of the present report. It is to be noted for example, that in this stratigraphic section (aggregating 1,745 feet) a rhythmic to truly cyclic pattern of recurrent thick-bedded and massive reefal and skeletal limestones, micritic limestones, silty to argillaceous limestones, and sandy limestones can be established. This section compares well with that illustrated and described by Mollazal (1961, p. 24-28) for the Ely at Conger Mountain, approximately 12 miles northeast of the Burbank Hills.
Nature and extent of possible cyclicity of the Hogan Formation has not been firmly established, although in Robinson's original description of the formation (1961, p. 98, 103-104), a distinctive pattern of repetitive sedimentation of silty limestone, calcareous sandstone, cherty limestone, and sandy limestone is readily discernible. This pattern is characteristic, as indicated by field investigations of the writer in some of the ranges of eastern Nevada and western Utah. One of the most characteristic sedimentary patterns of the Hogan is that of recurrent "lunch-meat" layers of brown-weathering chert, and discontinuous layered or blebby chert, interbedded in silty limestones, sandy limestones, and calcisiltites. Harmonious rhythmic sedimentation of silica and siliceous sediment is evidenced. The Strathearn Formation, likewise, has not been studied extensively or in sufficient detail across parts of northeastern Nevada and adjacent northwestern Utah to ascertain if cyclicity, or a diagnostic pattern at least, is demonstrable.
Ferguson Mountain Formation, mainly of Wolfcampian age, has a remarkably systematic, almost rhythmic, pattern of sedimentation displayed in the interlayered units. Although the formation was not named and described in detail until 1960 (Berge, 1960, p. 18-24), some of the lithic features of this superb surface section were mentioned and illustrated prior to that date (Bissell, 1959, p. 167-170). This section aggregates about 1,875 feet at the type locality (Fig. 2), and consists of thin- to thick-bedded and massive skeletal to micritic limestone, argillaceous limestone, siltstone, reefal limestone, detrital limestone, criquinite, and cherty lithoclastic limestone. Numerous details of lithology are provided by Berge (1960, p. 18-24), and of fusulinid paleontology by Slade (1961, p. 55-92), and these need not be repeated here. It is worthy of note, however, that cycles of sedimentation are shown to advantage in this stratigraphic section, and they consist normally of oopelletoid, algal, bryalgal, fusulinal, and coralgal limestone, silty detrital limestone, sandy micritic limestone to pure micrite, and massive cherty limestone. Cycles recur throughout much of the formation. Seemingly, variation in water depth (marine epineritic and marginal infraneritic) is indicated in fusulinid and other faunas, and rock types. It may have been that the hard, dense, siliceous limestones accumulated in deeper, or at least quiescent, waters, but that the fusulinid limestone formed in shallower depths. Under higher energy conditions the algal, bryalgal, coralline, coralgal, oopelletoid and related carbonates formed in still shallower epineritic waters.
Figure 2--Patterns of sedimentation in the Ferguson Mountain Formation at tpe locality in Elko County, Nevada. Triads and tetrads are rhythmically arranged in sequence.
An alternating and recurrent, and thus cyclic, tetrad consisting of reefoid, bioclastic, matrix, and micritic limestones is the essential pattern displayed in the sediments of the Ferguson Mountain Formation at the type locality. This tetrad recurs with remarkable simplicity, and at times rhythm, within the nearly equally spaced stratigraphic units.
Studies have not progressed far enough to permit more than basic assumptions regarding patterns of sedimentation of the Riepe Spring and Riepetown Formations of east-central Nevada and west-central Utah, so they are not discussed in this paper.
Some of the cardinal facets of stratigraphy and paleontology of the Pequop Formation have been discussed elsewhere, and the interested reader is referred to those papers (Steele, 1960, p. 106-107; Robinson, 1961, p. 93-145; Bissell, 1962b, p. 1094-1096). Cyclicity of sedimentation, as well as simple harmonic recurrent, not necessarily cyclic, patterns are evidenced; some of these are rhythmic. The middle (= Summit Springs) member of the formation best illustrates the patterns. This sequence, superbly exposed adjacent to US Highway 50 in the Moorman Ranch area northwest of Ely, Nevada (Bissell, 1962b, Pl. 3, Fig. 2), was chosen in the present study as a classic example. The cyclic (to rhythmic) pattern there normally consists of a thickness aggregating 1,000 to 1,200 feet of encrinal limestone, fusuline coquinite, sandy lithoclastic limestone, and micritic limestone (Fig. 3). Characteristic triads recur again and again, each consisting of sandy lithoclastic limestone at the base, criquinite with fusulinids, and micritic limestone. Where tetrads typify the section, calcareous sandstone is the basal unit beneath the sandy lithoclastic limestone. Seemingly, shallow-water, relatively high-energy sedimentary realms prevailed in this area during medial Leonardian time, although at times, and locally at least, quiescence dominated the regimen, as indicated by micritic, possibly chemically formed limestones. When traced in a northerly direction from outcrops near the highway, the Summit Springs Member is seen to contain interdigitated "primary" (= evaporitic) dolomite and other restricted environment sediments.
Figure 3--Cyclic patterns in middle (=Summit Springs) member of Pequop Formation in Moorman Ranch area, White Pine County, Nevada. Triads and tetrads characterize section.
Steele (1960, p. 106.107) proposed the name Loray Formation for a sequence of yellow-tan, gypsiferous silts and thin bioclastic limestones exposed at the head of Loray Wash in sec. 28, T. 38 N., R. 68 E., Elko County, Nevada. Certain details of extent, thickness, and lithology of this formation have been presented by Bissell (1962b, p. 1096-1097). More recently the writer has had opportunity to study the Loray in additional localities; the formation records a most interesting history of patterned sedimentation in the Cordilleran miogeosyncline during latest Leonardian and possibly earliest Wordian time. The Loray contains shale, claystone, siltstone, dolosiltite, evaporitic dolomite, gypsum, petroliferous limestone, and mollusk-bearing skeletal limestone arranged in a most unique pattern. The formation is normally at least 1,000 feet in thickness and is about 2,000 feet thick in the Butte Mountains of east-central Nevada. The recurrent pattern throughout a relatively large area testifies to cyclicity in the ancient depocenter under transgressive-regressive conditions; the net result ultimately being complete to near-complete withdrawal of marine waters from the geosyncline and shelf areas. Some sections contain records of 10 to 12 cycles, each normally consisting of sandy limestone that is of lithoclastic nature (at the base), argillaceous to silty-sandy skeletal limestone with nuculid pelecypods and straparolloid to small, high-spired gastropods, overlain in sequence by varicolored shale and siltstone, claystone, gypsum (or gypseous clayey limestone, locally a collapse breccia), "primary" (= evaporitic) dolomite, and argillaceous limestone which emits an hydrocarbon ordor when the rock is broken. Not all sections that have been studied to date contain outcrops of gypsum or gypseous sediment, but collapse breccia and earthy claystone are invariably present where gypsum does not crop out. Trenching in some of these nearly covered intervals invariably reveals gypsum or gypsiferous materials to be present. The cored interval in the test drilled by Standard of California-Continental Oil Company in the top of the Butte Mountains (sec. 30, T. 20 N., R. 60 E., White Pine County, Nevada) reveals substantial thicknesses of salt, gypsum, and other sediments arranged in cyclic pattern (Fig. 4).
Figure 4--Patterns of cyclic secimentation in Loray Formation, west side of Butte Mountains, White Pine County, Nevada. Evaporite suites are present.
An area of particular significance in the present study of patterned sedimentation for the Loray Formation is to the west and southwest of Ely, Nevada. Excellent outcrops, and some road-cut exposures, along and adjacent to US Highway 6 west of Murry Summit, particularly east of Giroux Wash, southwestern part of the Rib Hill area, and the north side of Lion Spring Wash, reveal at least 1,100 feet of interlayered, cyclically formed sediments in the formation.
Sediments of the Kaibab, Plympton, and Indian Canyon Formations display distinctive patterns, but they have not been studied in sufficient detail. McKee (1938, p. 129-132) has, however, discussed significance of distinctive cycles in the Toroweap and Kaibab Formations of northern Arizona and southern Utah, stating that ". . . the Toroweap and Kaibab Formations are thought by the writer to be true cyclothems, and the members which they include are therefore equivalent to the 'phases' of Moore, though they are much thicker. The cycle represented by the transition from red beds and gypsum deposits to marine limestones and back to red beds and gypsum forms a sequence which differs from that of the various Pennsylvanian cyclothems . . . not only in thickness of units but also in number and arrangement of units and in the matter of unconformities. In sequence it appears to be more nearly comparable with the Permian cyclothems of Kansas, whose 'phases' go from continental deposits to brackish-water deposits, to marine deposits, then back in reverse order." Studies by the writer of the Toroweap and Kaibab Formations of southwestern Utah and southern Nevada in general bear out this pattern of cyclicity, but perhaps the term "cyclothem" should not be used to embrace the sequence. Toroweap Formation is not recognized in east-central to northeastern Nevada and adjacent Utah, although Brill (1963, p. 325-326) indicates it may be represented in the Granite Mountain area of the northern Confusion Range in western Utah by about 25 feet of sandstone and limestone.
Steele (1960, p. 108-109) considers the Phosphoria Formation to have an areal extent of approximately 17,000 square miles in northwestern Utah and northeastern Nevada. Certainly this formation is present in the area of current consideration, but the writer includes some of the facies which resemble phosphatic shale and thin cherty phosphorite as southerly pointing tongues in the Plympton and Indian Canyon Formations. Cyclical patterns are demonstrable for the Phosphoria Formation in southern Idaho and immediately adjacent areas of northeastern Nevada and northwestern Utah, but they are not considered in this report.
Gerster Formation is uppermost in the Park City Group, and varies in thickness from 400 to more than 4,000 feet in western Utah and eastern Nevada; it contains a fascinating record of patterned sedimentation. These patterns are cyclically arranged tetrads of skeletal, lithoclastic, and micritic limestones, and arenaceous criquinites. The thinnest section of the Gerster Formation is at the type locality of the Gold Hill district of western Utah, and it thickens progressively westward through the Pequop Mountains to the thickness of more than 4,000 feet in the Medicine Range in T. 27 N., R. 61 E., Elko County, Nevada. The pattern as shown in this latter area is a recurrent, and cyclic, arrangement of skeletal limestones, rich in productid, compositid, and punctospiriferid brachiopods, overlain by lithoclastic sandy limestone, and this in turn by micritic limestone, and arenaceous criquinite. Seemingly the sandy criquinite represents highest energy of accumulation in the epineritic part of the depocenter, with diminution upward through skeletal limestone, sandy limestone, culminating in micrite. This tetrad pattern is repeated innumerable times in the 4,000-foot section, and thus records cycles and rhythms of sedimentation (Fig. 5).
Figure 5--Rhythmic cycles of Gerster Formation in Medicine Mountains, Elko County, Nevada.
The sedimentary pattern of Pennsylvanian and Permian rocks is substantially different in parts of Nevada such as in the Pancake Range west of Duckwater, Nye County, at Carbon Ridge and Sulphur Springs Range of Eureka County, and in the Diamond Range of Eureka, White Pine, and Elko Counties. In this area of north-south trend, sediments of the Ely, Arcturus, and Park City Groups (or age-equivalent strata) accumulated under diastrophic influences of the Antler and Sonoma belts. Thus, distinctive patterns of coarse-, medium-, and fine-textured sediments are evidenced. Moleen and Tomera for example, are typical and contain chert-pebble conglomerates within the carbonate sequence, emplaced in a cyclic to rhythmic fashion. The Riepe Spring, Riepetown, and Pequop Formations can be recognized locally; in fact, Steele (1960, p. 93) places them in his Carbon Ridge Group, thus raising the Carbon Ridge Formation of Nolan and others (1956, p. 64) to group rank. He assigned the Garden Valley Formation of Nolan and others (1956, p. 67) a Wordian to Capitanian age in his correlation chart (Steele, 1960, p. 93), but stated (p. 112): "The Garden Valley Formation presents many problems, for the age of this unit is middle Wolfcampian to possible lower Triassic." Four distinctive members typify the Garden Valley Formation: (1) a basal limestone; (2) a conglomerate, sandstone, and shale sequence; (3) a resistant siliceous conglomerate; and ( 4) a sequence of purple and red shale and conglomerate. Steele (1960, p. 112) correlated the basal member with the Riepe Spring Limestone, second member with the lower Plympton, the third member was stated to be upper Guadalupian, and the fourth member considered to be uppermost Permian or lowermost Triassic. Recent studies by the writer do not wholly harmonize with the conclusions of Steele, because in a measured section of approximately 6,000 feet, fusulinids of Wolfcampian to medial Leonardian age and a few megafossils indicative of early Guadalupian age were found. No paleontologic evidence of "uppermost Permian and lowermost Triassic" was found, and it is doubtful if highest strata of the Garden Valley Formation are younger than early Guadalupian, possibly Wordian age. The section which is illustrated (Fig. 6) in the present report does, however, illustrate the type of cyclic, rhythmic, harmonic patterned sedimentation. A rhythmic cycle here normally consists of a tetrad of conglomerate (at the base), sandstone, shale, and argillaceous limestone and skeletal limestone. This tetradal cycle is the component make-up of the formation, inasmuch as it consists of four cyclically arranged members.
Figure 6--Rhythmic patterns of sedimentation in Garden Valley Formation, Eureka, White Pine, and Elko Counties, Nevada.
Subsequent to deposition of the carbonates and related sediments of the Gerster Formation, and of those of uppermost Garden Valley Formation, complete withdrawal of marine waters from the Cordilleran miogeosyncline and shelf areas occurred in Guadalupian time. No record of Ochoan-age sedimentation has been found in the area under current study, and evidently such is lacking in the eastern Great Basin area. Thus, a hiatus of considerable time-span is represented in the areally extensive unconformity. Discussion of this great unconformity is presented elsewhere (Steele, 1960, p. 112; McKee, 1938, p. 54-61; Bissell, 1962a, p. 240-245; 1962b, p. 1103-1104; 1964, p. 632-634).
Figure 7--Paleotectonic setting during Pennsylvanian and Permian times for western Utah and eastern Nevada.
The writer (1962b, p. 1104) stated: "Periodicity of activity on the highlands accompanied by rapid removal of terrestrial materials and concomitant accumulation in the depocenters accounts for the 'cyclic' or 'rhythmic' sedimentation of Ely Limestone in some regions, such as near Elko, Nevada, and the Burbank Hills-Confusion Range area of western Utah." In his discussion of the cycles in the Ely and related formations in the eastern Great Basin, Brill (1963, p. 314) stated: "Cyclic sedimentation might be accounted for by postulating transgression and regression along an unstable border between shelf and subsiding basins; however, Imbrie and others (1959, p. 77), working in Kansas, question this rather obvious explanation." Peterson and Ohlen (1963, p. 74-79) favor the glacial-control hypothesis for cycles in the Paradox Basin of the Four-Corners area, stating: "Most of the Pennsylvanian carbonate section in the Paradox basin displays a strongly cyclic depositional history. This condition is especially well developed in rhythmic fashion in the Paradox evaporites and their equivalent facies throughout the basin . . . The orderly repetition of the cyclic layers (up to 35 in the Paradox evaporite section) is thought to be related to sea level changes probably caused by cycles of Carboniferous glaciation in the southern hemisphere . . ." In his discussion of the Paradox Basin cycles, Elias (1963, p. 188) stated: "It is the belief of this writer that the numerous cyclical deposits in the Pennsylvanian System of the Paradox Basin resulted from numerous transgressions and regressions of the sea, just as in the Midcontinent area." Elias was comparing the Paradox Basin cycles to the Kansas cyclothem, however, not attempting to apply the term cyclothem in the Paradox Basin, but to compare the two provinces in terms of depositional history. He believes that the Paradox Basin was a land-locked or at least fairly well-enclosed body of water during Middle Pennsylvanian time, with the Emery Uplift taking the role of a spit or bar, similar to the feature at the Gulf of Karabugas. His (Elias, 1963, p. 201) illustration bears out this idea, with possible straits (Oquirrh and Fremont) connecting the Paradox Basin with Cordilleran geosyncline; he added: "Any deepening of the water over the Emery positive area would have allowed freer intermingling of Cordilleran sea waters with those in the Paradox basin. Any shallowing at the threshold would have restricted exchange between the two water masses; excessive evaporation in the Paradox basin then would have resulted in the widespread precipitation of salts." Elias illustrated and discussed the bioherm-evaporite-tectonism relationship (p. 198), noting: "Since evaporites are likely to be deposited in submarine depressions, the synclinal position may suggest that the submarine depression was tectonically controlled and that it was into such tectonic sags that heavy salt-laden water flowed during the regressive phase of the depositional cycle. This concept is not out of harmony with the other evidence for the age of folding."
McKee (1938, p. 131) discussed the cycles of the Toroweap and Kaibab Formations of northern Arizona and southern Utah, and obviously did not favor the glacial-control hypothesis, for he stated: "The character of the sequence and also the relation of stages in sedimentation to periods of change in base level in the Permian are decidedly different from those in the Pennsylvanian. In addition to these differences, the great thickness of beds in most of the units of the Toroweap and Kaibab cyclothems argues strongly against glaciation as the cause." He summed his conclusion by stating (p. 131): "In brief, the writer believes that the most logical explanation for these cycles is to be found in earth movements in the region of deposition."
Evidence gained from field and laboratory studies in the region under current consideration conclusively proves in some areas, and strongly suggests in others, that periodicity of diastrophism of marginal and intra-basin landmasses as well as submarine diastrophism substantially controlled the pattern of sedimentation in depocenters of the Late Paleozoic miogeosyncline. Rhythmic, recurrent, and cyclic patterns in the Permian evaporites (Summit Springs Member of the Pequop Formation, and Loray Formation) seemingly are related to cyclical changes in the environment during fluctuations, orogenic and epeirogenic, of the depocenters. Climate, as well as tectonism, likely influenced the patterns developed in the basins and also in outlining the basins; aridity necessary for accumulation of evaporite suites was related to climatic changes, in part at least. Eustatic change of sea level may have exercised tremendous control during medial Permian time, and this may have been related to continental glaciation in the southern hemisphere, when sea level was substantially raised and lowered. It must not be overlooked, however, that a mechanism similar to that outlined by Elias (1963, p. 187-201) for accumulation of the evaporite cycles in the Paradox Basin of the Four Corners area could also have accounted for Permian evaporites in western Utah and eastern Nevada. Much can be said in favor of anticlinal-synclinal warping within the various depocenters of the Cordilleran miogeosyncline; distinctive patterns of sedimentation (not necessarily limited to evaporite suites) may have formed in the tectonically formed depressions and across the submarine banks, some of the latter conceivably being anticlinal warps.
Marine oscillations and concomitant transgressive-regressive sedimentation across the broad shelves, banks, basins, troughs, and evaporite pans established various patterns of carbonate and related sediment deposition in the geosyncline. In verity, the miogeosyncline--the eastern Great Basin portion of the Cordilleran geosyncline is an excellent example--is composed of these various elements. Rhythmic orogenic and epeirogenic activity of the Antler-Sonoma orogenic belt, Northeast Nevada Highland, West-Central Utah Highland, Ely Uplift and others (Fig. 7) provided detritus and otherwise initiated and controlled patterned sedimentation. Diastrophism within the Ely Basin, Oquirrh Basin, Wood River Basin, Bird Spring Trough, Arcturus Basin, Butte-Deep Creek Trough, and Park City Basin must have exercised tremendous influence at the times when transgressive-regressive sedimentation characterized areas during Pennsylvanian and Permian times.
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