Evaporite Salt Research Articles

Eolian dust in the coastal desert of the sudan: Aggregates cemented by evaporites

Eolian dusts collected after dust storms contain aggregates that are cemented by evaporitic salts, mainly halite. They vary in shape, fabrics, and surface roughness. Aggregation changes grainshape, density and size distribution of dust particles (i.e., characteristics determining erosion and transport); on deposition in the sea, cements dissolve and aggregates disintegrate, leaving the resultant eolo-marine sediment component with a misleading paleo-climatic record. The eolian transport of salts with dust from the arid coastal plain to the sea constitutes a portion of anticyclic salt movement and probably plays a role in the geochemical balance of the oceans.

Ignorance concerning episodes of ocean-wide stagnation

Episodes of basin-wide abyssal stagnation have occurred in the Mediterranean Sea during the “glacial” Pleistocene and on a much larger scale in the Atlantic and Indian Oceans during the Cretaceous Period. The sedimentary products of euxinification are organic-rich sapropels which have accumulated an order of magnitude more carbon during the Cretaceous than that which is present in all the known world reserves of coal and petroleum. The storage in the Cretaceous strata of excess carbon and sulfur in the form of fossilized photosynthetic substances and pyrite is thought to have led to a significant global increase in atmospheric oxygen and to an unusual sequence of calcium-rich evaporitic salts in the South Atlantic during the Aptian. Stagnant episodes in the Mediterranean and Atlantic effectively destroyed all benthic life formerly existing on substratums underlying hydrogen-sulfide bearing anoxic bottom waters. Locally thin organic-rich strata on topographic highs near the paleo-equator of the Pacific Ocean during the Cretaceous owe their origin to an intermittently expanding oxygen-minimum zone as contrasted to total euxinification within the deep basins of the Atlantic and Indian Oceans. In the context of both land and sea areas, the late Mesozoic may have conceivably been the major “carboniferous” period of the earth since the end of the Precambrian.

Io: A Surface Evaporite Deposit?

A model is suggested for Io's surface composition involving evaporite salt deposits, rich in sodium and sulfur. According to this model, these deposits were produced as a result of the migration of salt-saturated aqueous solutions to Io's surface from a warm or hot interior followed by loss of the water to space. This model satisfies cosmochemical constraints based on Io's initial composition, current density, and thermal history. Salt-rich assemblages are easily derivable from the leaching of carbonaceous chondritic material; the chemical and optical properties of such deposits, after modification by irradiation, can be used to explain Io's overall albedo and spectral reflectance, its dark reddish poles, and the observed sodium emission as well as or better than other currently suggested materials.

Upper Devonian Duperow Sedimentary Rocks in Southeastern Saskatchewan--Why No Oil Yet?: ABSTRACT

Although oil shows are common in the 500 to 700 ft thick Duperow Formation (Frasnian) of southernmost Saskatchewan, no commercially viable accumulations have been found. However, a few miles south of the Canadian border producing fields are present in Montana. The sedimentary rocks comprise more than 20 carbonate/evaporite cycles with potentially good reservoir rocks--sucrosic dolomites, oolites, and vuggy carbonates. The inhibiting factors to hydrocarbon accumulation are: (1) extensive anhydritization plugging pore spaces; (2) halite plugging vuggy carbonates in the upper Duperow; (3) many vertical fractures, now plugged by anhydrite, but good potential escape routes for fluids in the past; (4) absence of oolite developments more than 2 ft thick. These factors explain the lack of success to date. However, the Duperow still is considered a good prospect because: (1) good porosity and oil staining are common in two zones near the middle of the Duperow section; (2) only 180 wells have penetrated the Duperow over an area of 15,000 sq mi--35% of these have terminated above the porous zones, sometimes on seismic highs where the prospect was obviously the overlying Birdbear Formation, a known producer; (3) vuggy carbonate rocks may not always be halite plugged in an area southwest of a major halite body; (4) isopach maps show that extensive solution of Middle Devonian Prairie Evaporite salts took place in Duperow deposition causing locally anomalous accumulations of Duperow sediments. Structure contour maps indicate northwest and nor heast trends of the anomalies. These trends are strongly emphasized in a computer-plotted third-degree residual trend surface analysis map. A major northeast lineament lines up with the Duperow fields in north Montana. Conjugate sets of weakness in the Precambrian basement may have caused these trends, and their intersections are the most likely prospects for Duperow oil. End_of_Article - Last_Page 907------------

Eminence Dome - Natural-Gas Storage In Salt Comes of Age

These two salt-dome caverns in Mississippi have been solution mined specifically for storing natural gas under pressure. The pressure storage allows the gas to flow freely from the caverns as needed and keeps the water content of the produced gas at a minimum. Introduction By 1990, the U. S. will need annually almost three times as much natural gas as was sold during 1970. To meet such consumer demands during peak periods, huge storage facilities are needed. Solution-mined caverns constructed in naturally occurring subsurface salt formations has the potential for providing adequate storage. This concept has been providing adequate storage. This concept has been proved by the successful operation of several such proved by the successful operation of several such caverns in Canada and the U. S. Salt suitable for solutioning caverns is found in either of two forms salt domes and bedded salt deposits. There are 329 proved salt domes in the Gulf Coast area. Bedded salt deposits have been found in various parts of the U. S. Storage of gases and liquid hydrocarbons in solution-mined salt caverns was conceived during World War II, and by 1950 the use of such caverns in the U.S. was extensive. For more than 15 years, salt caverns have been used for storing liquefied petroleum gases such as propane and butane. petroleum gases such as propane and butane. The caverns are constructed by injecting fresh water into a salt formation and removing the resulting brine. A recent storage survey lists more than 500 of these caverns in operation, with a total storage capacity in excess of 5.25 billion gal. Only seven of these caverns, however, were developed for the storage of natural gas. The first use of a solution-mined salt cavern for storing natural gas was in 1961 when Southeastern Michigan Gas Co. leased, from the Morton Salt Co., and converted an abandoned salt cavern formed by routine brine production. The cavern, near Marysville, Mich., had a working capacity, after conversion, of about 341 MMcf of gas at a wellhead pressure of 1,100 psia and a minimum line pressure pressure of 1,100 psia and a minimum line pressure of 150 psia. The first such cavern created specifically for the storage of natural gas was constructed by the Saskatchewan Power Corp. and became operational in 1961 The 290,000-bbl cavern, located in Melville, Sask., was constructed in the Prairie Evaporite salt formation at a depth of approximately 3,700 ft. In the U.S., the first solution-mined salt cavern constructed specifically for the storage of natural gas was completed in the Eminence Salt Dome in Covington County, Miss., in 1970 by Transcontinental Gas Pipe Line Corp. After salt domes in Louisiana, Mississippi, and Alabama had been thoroughly investigated, Eminence Dome was chosen because: a seismic survey of the dome indicated sufficient salt for the caverns and for future enlargement; the salt was relatively shallow, with the top of the dome only about 2,400 ft below the surface; there was an adequate supply of fresh water for salt leaching brined-isposal wells could be completed in formations on the flank of the dome; enough land was available for all surface facilities; and the dome was near Transco's pipeline. Each of the caverns in Eminence Dome is operated "brine free"; that is, natural gas is injected into the caverns under pressure, which then causes the gas to flow from the caverns as needed. JPT P. 1299

Seismic Investigation of the Crater Lake Collapse Structure in Southeastern Saskatchewan

A detailed survey was carried out near Crater Lake, an unusual, circular depression 800 ft. (244 m) across, about 20 miles (~32 km) south of Yorkton, Saskatchewan. In-line and offset profiling with threefold subsurface coverage were used to outline this very small structure. The seismograms show a deep, narrow structural disturbance beneath the lake. This is interpreted as a chimney filled with breccia, which had collapsed into a solution cavern in the Prairie Evaporite salt over 3000 ft (914 m) below surface. About 125 ft (38 m) of salt has been removed from an area about 800 ft (244 m) in diameter. The chimney is about 350 ft (107 m) in mini mum diameter. Solution-collapse features are common in Saskatchewan, but previously none has been described that is so small or so well delineated on the surface. In northern Michigan, however, structures that are thought to be similar occur as columns of indurated breccia exposed by differential erosion.Small collapse structures present peculiar hazards to potash mining because they are very difficult to detect. There is also danger to roads and buildings should subsidence or sudden collapse occur in the future.

Can an Ocean Dry Up? Results of Deep-Sea Drilling in Mediterranean: ABSTRACT

Between 5 and 6 m. y. ago, at the climax of an episode of evaporite deposition, a series of events occurred on the floor of the Mediterranean Sea which left a fossil imprint reminiscent of a parched salina. The primary evidence of this unexpected happening was unearthed in the uppermost layers of a bedded sequence of evaporite salts of late Miocene age which were retrieved from beneath the present sea floor during Leg 13 of the Deep Sea Drilling Project. In continuous sections of core the shipboard scientific team discovered a remarkable transition from sterile chemical precipitates (gypsum, anhydrite, and halite) to deep-sea pelagic sediment. At all the sites drilled, the transition occurred between Miocene salts and Pliocene biogenic ooze. In the eastern Mediterranean, the transition consisted of a 10-cm thick zone of dolomite gravel containing littoral benthonic fauna. Beneath the Balearic abyssal plain in the western Mediterranean, the corresponding zone is a 2-m thick bed of flat-pebble conglomerate directly overlying a massive unit of current-bedded gypsiferous sandstone. In the central Tyrrhenian basin the transition involved a pebbly breccia composed of lateritic soils, strikingly similar in lithology to the limons rouges of littoral sequences in North Africa and Italy. The most plausible explanation of these findings is that a once actively precipitating deep brine basin became choked off from the open ocean and evaporation continued to the point of desiccation. Thereafter, the newly formed desert disappeared under a major marine inundation. End_of_Article - Last_Page 362------------

Evaporite Deposition from Layered Solutions

It is widely accepted that carbonates, especially those which originate as banks or reefs, and the evaporites with which they are closely associated represent mutually exclusive, successive phases of deposition: (1) a stage of carbonate bank or reef deposition under conditions of normal marine circulation, followed by (2) a time of sulfate deposition under conditions of restricted circulation, (3) an episode of further restriction leading to chloride precipitation, and, in some instances, ending in (4) an ultimate stage of bittern-salt accumulation. A multistage history of carbonate-evaporite deposition requires paleogeographic interpretations that appear bizarre in view of the epeiric setting of most deposits. An alternative is sought in deposition from density-layered waters with an upper layer of nearly seawater salinity and a lower layer or layers saturated with respect to one or more evaporite salts. Brine is supplied to such a system by evaporation on shelf areas surrounding a basin, and saturation is maintained by contact with salts on the basin floor. In this manner layered solutions persist for geologically significant spans of time, in spite of diffusion and mixing, while carbonate deposition continues in the upper dilute waters. Episodic exposure of the lower brine to evaporation is required for evaporite deposition. S ch exposure may be the result of displacement of the upper layer by wind, or may accompany long-period, high-amplitude, internal seiches. Layered systems and the effects of winds and internal seiches are demonstrable in present-day saline lakes; the processes involved are amenable to laboratory investigation.

Deep-Water Evaporite Deposition: A Genetic Model

Reasoning by analogy with modern salinas, many geologists believe that ancient marine evaporite deposits formed in shallow, slowly subsiding basins in regions of arid or semiarid climate. If this model is considered critically in the light of knowledge of several well-studied ancient deposits, however, inconsistencies arise which suggest the need for an alternative hypothesis. Sedimentation rates inferred from ancient salt deposits appear to be compatible with temperate rather than arid climates. More significantly, the thickness of evaporite salts in many localities requires either extremely rapid subsidence or salt deposition over a period substantially longer than that permitted by present stratigraphic control. In addition, the petrography, stratigraphy, and bromine content of the halite in such basins can be reconciled with the salina model only with great difficulty. The observed inconsistencies may be overcome by postulating that the salts were deposited in basins several hundreds to several thousands of meters deep. A model of evaporite deposition is shown to be both geologically reasonable and oceanographically tenable, and to be consistent with the depositional histories of the Zechstein, Salina, Castile, and at least part of the Elk Point evaporites. Direct stratigraphic evidence of deep-water deposition is available in the Castile Sea. The Elk Point (Prairie or Muskeg) Evaporites of Alberta are examined in the light of the deep-basin model, and implications of the model for the exploration geologist in the region are developed.

Evaporite Deposition in Deep Water: ABSTRACT

Reasoning by analogy with modern salinas, most geologists believe that ancient marine evaporite deposits were formed in shallow, slowly subsiding basins in regions of arid or semiarid climate. When this model is applied to several well-studied ancient salt deposits, however, inconsistencies arise which suggest the need for an alternative hypothesis. Sedimentation rates inferred for the Zechstein salts of Germany and the Salina of Michigan appear compatible with temperate rather than arid climates. More significantly, the thickness of evaporite salts in each of these localities requires either extremely rapid subsidence of the evaporite or salt deposition during a period of time substantially greater than that permitted by existing stratigraphic control. In addition, the petrography and bromine content of the halite in both basins may be reconciled with the model only with great difficulty. Most of the inconsistencies observed may be overcome by postulating salt deposition in a several hundred to several thousand feet deep. A basin model of evaporite deposition is developed in detail. The model is shown to be both geologically and oceanographically reasonable, and to be consistent with at least part of the depositional history of both Zechstein and Michigan evaporite basins. Direct stratigraphic evidence of deep-water evaporite deposition in the Midland is cited in further support of the model. The Elk Point evaporites of Alberta are examined in the light of the deep model, and certain implications of the model for the exploration geologist in this region are developed. End_of_Article - Last_Page 549------------

Hummingbird Structure of Southeast Saskatchewan

ABSTRACT Saskatchewan's first Devonian oil pool was discovered September, 1966 at Hummingbird, 45 mi southwest of Weyburn, Saskatchewan. The Hummingbird structure, located on the northwest flank of the Williston basin, is domal in nature and covers approximately 1 sq mi. Oil production is from two zones. The Ratcliffe Member of the Mississippian Charles Formation produces from an average of 49 ft in an algal and bioclastic limestone. The Devonian Birdbear Formation produces from an average of 56 ft in a fine-crystalline, vuggy dolomite. The Hummingbird structure is not diastrophic in nature. Rather, it is a sedimentary structure resulting from multiple-stage salt solution and collapse. Recurring local solution of Middle Devonian Prairie Evaporite salt during Late Devonian and Early Mississippian time resulted in collapse of overlying strata and deposition of compensating thicknesses of Souris River, Duperow and Bakken sediments. Between Mississippian and Cretaceous time, solution of Prairie Evaporite salt in the surrounding area caused collapse of all post-Prairie Evaporite beds. The extra Souris River, Duperow and Bakken strata at Hummingbird created the structure. Vertical migration of formation waters along a high-angle fault is suggested as the cause of the local salt solution at Hummingbird.

Evaporite salts from the dry valleys of Victoria Land, Antarctica

Evaporite salts from the dry valleys of Victoria Land, Antarctica

Sedimentation and Economic Prospects of Middle Devonian Winnipegosis Formation of Saskatchewan: ABSTRACT

The Middle Devonian Winnipegosis Formation of Saskatchewan is divisible into upper and lower members on the basis of a regionally developed argillaceous interval which forms the uppermost part of the lower member. The lower member consists of a regionally dolomitized marine carbonate of relatively constant thickness and lithology, attaining a maximum observed thickness of 54 ft. The upper member is a varied marine carbonate sequence, with three major facies developments. In the southwest lies a wedge of lithologically relatively consistent carbonates, reaching a maximum thickness of about 130 ft. along a northwest-trending axis extending through Weyburn and Elbow. In the north and east, bioclastic-pelletoidal carbonate banks with true reef intervals (up to 345 ft. thick), and finely laminated, interbank carbonates (up to 68 ft. thick) occur. The lower member was laid down in a broad epicontinental sea. The relatively shallow, open marine conditions culminated on two occasions in basin-wide, reducing, lagoonal conditions, evidenced by the medial and upper very bituminous argillaceous intervals containing impoverished faunas. The upper member appears to have been deposited in a shallow shelving sea which deepened toward the northeast. Using a regionally developed Amphipora zone as a datum, three pre-Amphipora tectonic-sedimentational regions are discernible: in the southwest, the Elbow-Weyburn basin, subsiding relatively rapidly to accommodate thick, shallow-water carbonates; in the north and east, the comparatively stable Saskatoon shelf, with thin laminated carbonates and basal carbonates of the bank sediments; and the mo e rapidly subsiding Meadow Lake-Sayese basin complex, with similar sediments, except that bank sedimentation was further advanced. In post-Amphipora time, subsidence continued in the north, accelerated in the shelf area to accommodate thick bank accumulations, whereas, in the southwestern basin, carbonate deposition was almost complete. Although no commercial quantities of oil or gas have been found in Saskatchewan, production of oil from the Winnipegosis in the Outlook and Redstone fields of northeastern Montana is encouraging. The occurrence of oil and gas shows in some drill-stem tests and of oil staining in the Winnipegosis Formation in Saskatchewan offers further encouragement, especially in the Elbow-Weyburn basin, which is a northwestern extension of the oil-producing facies of northeastern Montana. The presence in the southwestern basin of permeability traps resulting from differential dolomitization and recrystallization, and in the north and east, of important thickening in short distances, associated with variably porous bank carbonates, together with the widespread development of an excellent top seal i the form of the Prairie Evaporite salt or carbonate-anhydrite sequences, provide excellent conditions for the entrapment of hydrocarbons. End_of_Article - Last_Page 1570------------

Exploration for Evaporite Salts in Green River Basin, Wyoming: GEOLOGICAL NOTES

Exploration for Evaporite Salts in Green River Basin, Wyoming: GEOLOGICAL NOTES