Dolomite Member Research Articles

Redescription and New Nomenclature of Manitou Formation, Colorado: GEOLOGICAL NOTES

Redescription of the type section of the Manitou is necessary because the original description was highly generalized and unuseable for detailed correlation and environmental interpretation. Separated in the macroscopic and petrographic redescription are 24 units compared with two units suggested in the original description. The word Formation rather than the original Limestone is used as part of the formal name because of the wide variety of lithologies now recognized in the type section. Physical correlation of the Manitou within a southeastern facies has demonstrated that two previously unnamed members are easily recognized in the field. These members are described from a section at Horseshoe Mountain in Park County, Colorado, and assigned the new names Ptarmigan Chert Member and Leavick Tarn Dolomite Member.

Microbiota from the Late Proterozoic Tindir Group, Alaska

Preliminary investigation of carbonaceous sediments from the late Proterozoic Tindir Group, east-central Alaska, reveals the presence of abundant single-celled and spherical colonial nannofossils interpreted to represent blue-green algae. Similar micro-organisms, particularly Sphaerocongregus Moorman, have been reported from the late Proterozoic Hector Formation of southwestern Alberta, Canada. The fossils reported here come from beds tentatively considered to represent the upper Tindir Dolomitic Sandstone and Shale member, stratigraphically above the Basalt and Red Beds member, for which an age of no more than 850 m.y. has been suggested. However, it is possible that the fossiliferous sequence is correlative with the lower Tindir Dolomite and Shale member which immediately underlies the Basalt and Red Beds member, and which contains a stromatolitic structure known in beds 950 m.y. old and older elsewhere.

Hydrogeologic Factors Influencing Well Yields in Folded and Faulted Carbonate Rocks in Central Pennsylvania

Hydrogeologic factors influencing well yields in folded and faulted Cambro‐Ordovician carbonate rocks and shales were investigated in central Pennsylvania. Productivity values (in gallons per minute per foot of drawdown per foot of saturated thickness) were obtained from 80 wells, the geometric mean value being 19.00, and were grouped into various categories according to well location. Productivities for the various categories were ranked and plotted against the percentage of wells on logarithmic probability paper. Parametric and nonparametric statistical tests were applied; the results of the nonparametric tests are presented. Fracture trace wells were more productive than nonfracture trace wells. Accidentally located fracture trace wells were as productive as intentionally located fracture trace wells because the accidentally located wells were clustered in more productive rocks. The success ratio of accidentally locating a fracture trace well is 4:6. Wells in sandy dolomite and coarse‐grained dolomites were the best producers; wells in valley bottoms were more productive than those in valley walls and uplands; anticlinal wells were better producers than synclina wells; and wells in beds dipping at less than 15° had higher yields than others. The Upper Sandy dolomite member and the Nittany dolomite have similar aquifer characteristics, which are significantly different from those of Bellefonte dolomite, limestones, and shales.

Trends of Faunal Morphologic Variation and their Environmental Significance: Key to Paleoecologic Analysis: ABSTRACT

Analysis of trends of morphologic variation within faunal assemblages is significant for paleoecologic interpretation, and complements paleoenvironment interpretations based on analogy with Holocene sedimentary environments. The Rondout Formation (Late Silurian), Hudson Valley, New York, demonstrates the importance of such analysis. The Glasco Limestone Member (12 ft) records offshore subtidal deposition. It is overlain and underlain by supratidal mudflats--the Whiteport Dolomite (1-7 ft) and Rosendale Dolomite Members, respectively. Within the Glasco, 5 units in vertical sequence from base to top show morphologic variation of halysitids, coenitids, stromatoporoids, and various algae, coincident with shallowing: Unit I (1 ft), amoeboid stromatoporoids in wackestone matrix; Unit II (4 ft), thin, laminar stromatoporoids, head-shaped halysitids, encrusting algae, and small-diameter branching coenitids in packstone and grainstone matrix; Unit III (1 ft), halysitids change to blade morphology; Unit IV (4 ft), no halysitids, bloom of larger diameter branching coenitids, branching and encrusting algae, and laminar and amoeboid stromatoporoids in packstone and grainstone matrix (rare wackestone); Unit V (2 ft), massive domal stromatoporoids in calcareous shale. Transitions from heads to branches, from heads to blades, from smaller to larger diameter coenitids, and from encrusting to branching algae are interpreted as adaptation to increased turbulence. Halysitid establishment and laminar stromatoporoid morphology correlate with firm substrate. A soft substrate supported amoeboid stromatoporoids. A decrease of turbulence permitted vertical expansion of stromatoporoids to domal morphology. Paleoecologic interpretations based on single morphologic occurrences, as contrasted with trends, must be made with reservation. End_of_Article - Last_Page 850------------

Reworked Lower Devonian Fossils, Nopah Range, Inyo County, California: GEOLOGICAL NOTES

Lower Devonian brachiopods, correlative with the Trematospira Zone of Oriskany age of central Nevada, were found in the basal dolomitic sandy member of the Devonian section in the northern Nopah Range of southeastern California. The fossils show physical evidence of reworking and are judged to have been derived from nearby areas where similar fossils are known to be present at the top of the Hidden Valley Dolomite.

Textural and Reservoir Variations of Ordovician Microdolomites, Lake Alma-Beaubier Oil-Producing Area, Southern Saskatchewan: ABSTRACT

The stratigraphic accumulation of oil in the upper Red River Formation of the Lake Alma-Beaubier region of southern Saskatchewan, Canada, is controlled by textural variations in the medial argillaceous or earthy dolomite member which separates the underlying, mottled, extensively burrowed, skeletal micrograined, dolomitic limestone of the Yeoman beds from the overlying interior anhydrite-carbonate rhythms of the Herald beds. Lenses of oil-saturated, coarse chalk to finely microgranular, calcareous dolomite (grain size 15-25 µ) pass vertically and laterally into micrograined (silt and clay intermixture) carbonate, and finally to cryptograined (less than 5 µ), commonly varved, dolomite. End_of_Article - Last_Page 745------------

Madison Limestone (Mississippian), Wind River, Washakie, and Owl Creek Mountains, Wyoming

The Madison Limestone of west-central Wyoming forms a wedge-shaped body of carbonate strata that tapers unevenly from a thickness of approximately 900 feet at the northern end of the Wind River Mountains to about 500 feet at Wind River Canyon and less than 200 feet in the Rawlins Hills. This thinning is mainly the result of a progressive decrease in the sedimentation rate but also has been affected by removal of at least 250 feet of rock from the top of the formation at some localities by post-Madison, pre-Amsden erosion. The formation becomes progressively more dolomitic southeastward along the Wind River Mountains and eastward along the Owl Creek Mountains, but this facies trend is reversed in the Rawlins Hills. A dolomite member is recognized at the base of the formation. Two distinctive lithic units in the upper half of the formation are interpreted as solution zones that were affected by the leaching of evaporite beds during post-Madison, pre-Amsden karst development. These solution zones are correlated with similar solution zones in the Mission Canyon Limestone in the type section of the Madison Group at Logan, Montana, and with evaporite intervals in the Mission Canyon at Hoback Canyon, Wyoming. Two faunal zones, the Spirifer cf. S. madisonensis Zone and the Diphyphyllum Zone, in the upper part of the formation are of great value for local and regional correlation. The Sacajawea is here used in the sense of Strickland (1957) as a member of the Madison Limestone and includes the uppermost beds of the Madison. A revised interpretation of the age, correlation, and geologic significance of this unit is supported by a thorough study of the Sacajawea problem. Corals and brachiopods collected from the Madison of west-central Wyoming suggest that the upper part of the formation is correlative with the Mission Canyon Limestone of Montana. However, the lowermost part of the formation contains Kinderhook conodonts at some localities and may be the same age as a part of the Lodgepole Limestone of Montana. The position of the boundary between Mission Canyon and Lodgepole age equivalents in west-central Wyoming is not indicated by available data.

Willow River Dolomite: Ordovician Analogue of Modern Algal Stromatolite Environments

The Willow River Dolomite Member of the Shakopee Formation (Lower Ordovician) in the Upper Mississippi Valley is composed primarily of dolomite and quartzitic dolomite with minor amounts of quartz sandstone, shale, and chert. Locally abundant algal stromatolites are the only common organic remains. Complete dolomitization has not destroyed the textural character or much of the compositional character of the rocks. As a result, environmental interpretations are possible from data gathered by examining thin sections as well as from field observations. Deposition of Willow River sediments took place in a shallow, epeiric sea consisting of three broad environments: (1) a shallow, open marine area in the northwest represented by grain sparite, abundant oölite beds, and relatively abundant fossils; (2) an intertidal or near-intertidal, high physical-energy zone where stromatolitic algae flourished in the central area represented by abundant algal biolithite with associated intrasparite; and (3) a locally intertidal and hypersaline, low physical-energy zone in the southeast represented by algal mats, micrite, and abundant desiccation features. Terrigenous materials were derived primarily from Precambrian igneous and metamorphic rocks and Cambrian sandstones to the northeast. General environment of deposition during Willow River time was similar to that in which other Lower Ordovician strata were deposited in the Appalachian, Ozark, and central Texas areas.

Revision of Lower Ordovician Nomenclature in the Upper Mississippi Valley

Detailed study of more than forty exposures in the upper Mississippi valley area suggests a logical solution to stratigraphic nomenclature of the Lower Ordovician (Prairie du Chien) strata of this area. Examination of the type area of the Shakopee Formation indicates that strata cropping out in Shakopee, Minnesota, belong to the upper carbonate unit of the Prairie du Chien. The Prairie du Chien Group is comprised of the lower Oneota Dolomite and the upper Shakopee Formation. The Shakopee is subdivided into the New Richmond Sandstone Member and the Willow River Dolomite Member.

Lower Clinton (Silurian) Relationships In Western New York and Ontario

A new interpretation of Silurian Lower Clinton relationships observed in the area between Medina, New York, and Clappison9s Corners, Ontario, is presented. The Lower Clinton Group in this area is considered to include those units between the Thorold Sandstone and the Irondequoit Limestone. The profound lithological and faunal differences between the Lower Clinton strata of western New York and those of the Niagara Peninsula in Ontario are probably the result of deposition in a shallow basin under conditions controlled by proximity to the Cataract shelf (Bolton, 1957). The influence of this shelf extended south and east of Hamilton, Ontario; its effect was felt at the beginning of Early Clinton time. Frequent slight changes in the elevation of the shelf area and the nearby depositional basin to the south and east resulted in fluctuations in strand lines and reworking and removal of some units. Supporting evidence includes thin conglomerates at several contacts, wedging out or overlap of lithologic units, and changes in fauna of successive units. The Reynales Formation between Medina, New York, and Clappison9s Corners, Ontario, is restricted and redefined to include only the lower, fossiliferous, limestone units which are here designated the Hickory Corners Limestone Member (new name) and the Merritton Limestone Member (new name). The upper more dolomitic and less fossiliferous unit, herein named the Rockway Dolomite Member (new name), is removed from the Reynales and is considered to be the lower member of the Upper Clinton Irondequoit Limestone.

Proposed Stratigraphic Nomenclature for Lockport Formation (Middle Silurian) in New York State: GEOLOGICAL NOTES

The Lockport Formation in New York extends from Niagara Falls 200 mi eastward to Ilion Gorge where it pinches out. Within the Lockport vertical and lateral lithologic differences permit recognition of members. At Niagara Falls the formation is 200 ft thick and consists of 5 dolomite members, in ascending order, the Decew, Gasport, Goat Island, Eramosa, and Oak Orchard. Farther E. at Rochester, the Lockport comprises the DeCew, Penfield (new name), and Oak Orchard members. From the Clyde to Oneida quadrangles, the limestone and dolomite facies are placed in a new member, the Sconondoa. The eastward-thinning Ilion Member of shale and dolomite occurs in the Rome, Utica, and Winfield quadrangles. E. of the Winfield quadrangle the Lockport is absent but its stratigraphic position is believed to be occupied in part by the upper Herkimer Sandstone (Clinton) and in part by the Herkimer-Brayman (Salina) disconformity.

Cyclic Sedimentation of Primary Dolomite and Limestone

ABSTRACT Cyclic repetition of limestone and dolomite was studied in a railroad cut near Charlton, Maryland. 35 cycles were recognized, each composed of a basal dolomite member and an upper limestone member. Field and petrographic evidence suggests a primary origin for the dolomites in the section studied. The cyclic repetition of dolomite and limestone, it appears, was due to tectonism.

Stratigraphic relationships of the Lower Ordovician Chipman Formation in west-central Vermont

The Chipman formation includes 4 members: the Burchards, characterized by limestone with dolomitic mottling; the Weybridge, composed of limestone with thin interbeds of sandy limestone; the Beldens, made up of interbedded limestone and massive dolomite; and the Bridport dolomite member, consisting of massive dolomitic beds, which in the Cornwall area interfinger with limestones of the Chipman formation. Nearly a century ago Augustus Wing correlated strata of the Weybridge and Beldens with those of the Bridport dolomite. This correlation has been recently reaffirmed by Marshall Kay, who also recognized the faunal affinity of the Weybridge member of the Chipman with late Beekmantown age. Recent mapping by the authors, particularly by Zen in the Sudbury Brandon area, shows that the sequence of the Burchards, Weybridge, and Beldens members, though generally in about that order, is locally much varied; also the Weybridge is locally missing in western areas and the Burchards is missing in some areas to the E. The irregular distribution of the Burchards, characterized by localized fossils, suggests biostromal deposits. These deposits apparently formed offshore from the Bridport dolomite member, which was deposited in nearshore shallows that fringed the eastern Adirondack area.

A Middle or Lower Devonian Psilophyte Flora from Central Arizona and its Paleogeographic Significance

An assemblage of fossil plants has been discovered about 16 feet above the base of the Devonian section in central Arizona. This section, at the mouth of Flying V Canyon, is rediscribed, and rocks of the lower portion are reported in detail. All Devonian deposits in this region have previously been assigned to the Upper Devonian series, but the plant fossils reported here indicate either Middle or Early Devonian age for the basal part. The plant fossils are at the base of the lower dolomitic member of the Martin formation as denned by Huddle and Dobrovolny (1952). This member is the stratigraphic equivalent of the lower part of the Jerome formation of Stoyanow (1936). Thus it is evident that sedimentation began no later than in Middle Devonian time over a wide area in central Arizona. The plant assemblage consists of branching axes similar to Hostimella and Aphyllopteris; of fertile structures comparable in organization to Cooksonia, Hicklingia Rhynia, Dawsonites, and Hedeia; and of isolated megaspores and meiospores evidently representing several kinds of terrestrial plants. A singular type of fungus-like microfossils, resembling Tasmanites and Leiosphaera in its composition, is also present. The character of the assemblage is evident, but several genera probably are new, and a later taxonomic report is planned. The plant fossils and lithologie facies suggest that the environment of deposition was essentially estuarine or lagoonal. Sedimentation seems to have been continuous between the time of deposition of the plant-bearing bed and the deposition of the marine beds above that contain Late Devonian fossils. A further study may indicate the position of the boundary between the older and younger Devonian series.

Silicification in the Oneota dolomite [Wisconsin

A short description of silicification in the Oneota dolomitic member of the Lower Ordovician Prairie du Chien group in the form of silicified stromatolite colonies and chert nodules near El Paso, Wisconsin is given. The occurrence of chert pebbles showing dehydration cracks and other evidence indicate that silicification took place during the time of the sedimentation.

Devonian Correlations in Wyoming-Montana-Alberta-Saskatchewan: ABSTRACT

Regional correlations in the Devonian have been obscured by diversity of treatment and the erection of numerous names for local lithologic developments. Broad-scale studies suggest that four operational rock units can be carried over much of the area and that these form a rational basis for analysis of the complex stratigraphic problems involved. Four units are recognized. (1) A basal including the Basal Devonian unit and Dc of Montana. Ghost River formation of the Alberta mountain front, and Elk Point and equivalent units in the Alberta-Saskatchewan subsurface. (2) A lower limestone including the limestone member of the Jefferson formation, the Fairholme formation (minus uppermost beds), and lithologic equivalents in the subsurface. (3) A dolomite-evaporite including the dolomite member of the Jefferson (plus evaporite-breccia zones in the lower part of the Three Forks), the lower part of the Darby formation of Wyoming, the Potlatch anhydrite, Morro member of the Palliser and Alexo silt of the Fairholme, and lithologically equivalent subsurface units. (4) An upper post-evaporite including the upper part of the Three Forks formation, the End_Page 1106------------------------------ upper Darby, the Costigan member of the Palliser, and equivalent clastic and non-clastic beds between the top of the anhydrite and the base of the Exshaw shale in the subsurface. An attempt is made to refine correlations by tracing of cyclical evaporite deposits, widespread clastic zones, and biostromal and fossiliferous-fragmental limestones. End_of_Article - Last_Page 1107------------

South Canyon Creek Dolomite Member, A Unit of Phosphoria Age in Maroon Formation Near Glenwood Springs, Colorado

The South Canyon Creek dolomite member of the Maroon formation crops out at many places from South Canyon Creek, which is 4½ miles west of Glenwood Springs, Colorado, northwestward for 22 miles. The thickness of the member ranges from 1½ feet to 6 1/3 feet. The member commonly consists of a basal unit of medium gray, very fine-grained dolomite; a middle unit of light gray to light buff, dense dolomite; and a top unit, 1 foot or less thick, of thinly laminated fossiliferous limestone having an undulatory or wavy structure, suggesting an algal origin. A preliminary study of the fossils collected from the member has yielded a tentative list of 24 forms, comprising 19 pelecypods, 2 scaphopods, and 3 gastropods. The fauna appears to be a Permian one of Phosphoria age

GEOLOGY OF THE PALEOZOIC ROCKS, LOGAN QUADRANGLE, UTAH

The succesion of Paleozoic strata in the Logan quadrangle, northern Utah, is one of the thickest and best exposed in the western United States. It includes 16 formations, representing every system of the Paleozoic except the Permian. Measurable sections of these formations have a total thickness of 23,200 feet. Here most of the formations are better exposed than in the area, contiguous to the Logan quadrangle at its northeasteastern corner, where Mansfield made his phosphate studies. These formations are described in detail. The Swan Peak formation (Ordovician) is divisible into three members; the Jefferson formation (Devonian) is divided into two members—the Hyrum dolomite member below and the Beirdneau sandstone member above. For the Lower Devonian rocks of the area a new formation, the Water Canyon formation, is defined. The Upper Mississippian rocks, called the Brazer formation, are 3700 feet thick at one locality in the quadrangle, a much more complete exposure than at the type locality of the formation in the Randolph quadrangle to the east. Pennsylvanian rocks reach a total thickness of 6000 feet in this area. A stromatolitic limestone in the Wasatch conglomerate is named the Cowley Canyon limestone member. The structures of the area include folds and overthrust faults produced in the Laramide deformation and high-angle faults of the Basin-and-Range type produced late in the Cenozoic. The major Laramide folds are the Logan Peak syncline and the Strawberry Valley anticline. Overthrusting appears to be responsible for separating the homoclinal masses that constitute the mountains of the west side of Cache Valley. The principal high-angle faults are defined as the East Cache, Hyrum, Wellsville, Dayton, and Clarkston faults. A resume of the geologic history of the area includes the recognition of two erosion surfaces—the Rendezvous Peak surface (late Tertiary) and the McKenzie Flat surface (Quaternary).

Structural control and wall-rock alteration at the Wilbert Mine, Dome District, Butte County, Idaho

The ore at the Wilbert mine in Butte County, Idaho, consists largely of fine-grained galena deposited mainly by replacement of a dolomitic member in a thick series of complexly folded and faulted Ordovician quartzites. Ore has been mined almost continuously from the surface to a depth of 800 feet and laterally for a distance of about 2,000 feet. In the upper levels the ore bodies have been localized by fracture and breccia zones along the crest of a sharply bent, overturned anticline, in the intermediate levels by a fissure in the plane of a curved thrust fault, which lies on the underside of the overturned anticline, and in the lower levels by a weak zone of fracturing and slipping along the contact of dolomite with overlying quartzite. The fracturing along the contact has apparently been localized by a minor bend in otherwise uniformly dipping beds; the ore body extends laterally downward at first and then assumes a horizontal position in the deep part of the mine.Mineralization was accompanied by marked alteration of the dolomite, which was feldspathized, carbonatized, silicified, and somewhat sericitized and pyritized prior to ore deposition. Feldspathization apparently was accomplished by high-temperature solutions emitted during a late stage of magmatic differentiation and was followed by intrusion of lamprophyre. Subsequent carbonatization and silicification (chiefly chalcedonization) apparently took place at relatively low temperatures.The mineralization is probably related genetically to early Tertiary magma, and ore deposition apparently occurred at moderate depth under essentially telethermal conditions.

STRATIGRAPHY OF THE UPPER CAMBRIAN, LLANO UPLIFT, TEXAS

The two formations and eight members that constitute the Upper Cambrian in the Llano uplift of central Texas are described or redefined, and their lithic characters in 19 measured sections are graphically summarized. Standard reference to them is thus furnished. The Riley formation comprises the basal Paleozoic strata of the Llano uplift. Its initial sediments were deposited on a submerged pre-Cambrian terrane having a known topographic relief as great as 800 feet. Its thickness normally averages about 680 feet but ranges from probably less than 200 to about 800 feet. At most places it is subequally divisible between the Hickory sandstone member below and the Cap Mountain limestone member above, with the thin but widespread, glauconitic Lion Mountain sandstone member capping and completing the sequence. The Wilberns formation includes five named members between the Riley formation and rocks of the Lower Ordovician Ellenburger group. It normally averages about 580 feet thick and ranges from 540 to 610 feet thick, but in the southeastern corner of the Llano uplift truncation of the upper beds has reduced it to 360 feet. The thin but widespread, nonglauconitic Welge sandstone member introduces the sequence. Above it is the Morgan Creek limestone member, grading to the succeeding argillaceous beds of the Point Peak shale. At the top of the sequence are the San Saba limestone and Pedernales dolomite members. These two are essentially equivalent and gradational facies, with the Pedernales normally overlying the San Saba.