CHAPTER 8

EVAPORITES*—OCEAN-FLOOR AND
CONTINENTAL TYPES OF SALT DEPOSITS

One of the most obvious and easily understood forms of sedimentary evidence for very long periods of time in earth's history is the existence of multiple-layer, thick beds of evaporite* minerals in many parts of the world. Nearly all of these layered deposits are composed mainly of salts which very obviously have been deposited by extensive evaporation of seawater in ancient shallow seas. The multiple (and diverse) layers of these cyclic deposits show that there were many changes of environment during the depositional process, and both seasonal and long-term climatic changes are represented in the layering of most such evaporite formations. (It is highly significant that sedimentologists have now reported on at least several places where this kind of deposition of evaporites is now occurring,forming annual couplet layers of evaporite and other related sediment season-by-season. One of these research reports is that of Kushnir (1981), and others will be cited farther along in this chapter.)

The existence of these ancient deposits—some of which are hundreds of feet in thickness and of wide areal extent—is of course a very perplexing problem for those who try to explain the earth's sedimentary cover as having been formed by the Flood. Consequently, most young-earth creationist writers have not referred to these formations, and apparently have not studied the geologic research reports which describe either ancient or recent evaporite deposition.

1. Halite (Sodium Chloride) Deposits of the Deep Ocean Floors

Henry Morris, realizing that geologists have described some kinds of salt deposits as having been formed by natural evaporation, has included a few pages of discussion on the great, non-cyclic deposits of halite (sodium chloride) in his Scientific Creationism (Morris, 1974, pp. 105-07). He cites certain evidences which indicate that at least some of these halite deposits were likely formed deep in the ocean floors from the release of salt "from great depths along faults during tectonic movements" (p. 106). Morris's main source of information for this is the Soviet scientist V. I. Sozansky, who made a careful study of halite deposits which lie in the deep ocean floor of the western Atlantic. Morris uses Sozansky's work in an attempt to nullify the evidences for the formation of evaporite deposits by natural evaporation.

What Sozansky has said about the halite deposits observed in his study appears to be correct, but Morris has erroneously assumed that a description of how halite salt deposits which lie deep in the ocean were formed also applies tothe cyclic deposits of anhydrite* (calcium sulfate), gypsum, calcium carbonate, and some halite layers, which are found far inland on the continents. (These continental deposits are found extending across broad areas which were once covered by shallow inland seas, in Canada, the United States, Australia, and other parts of the world.) Actually, there is little resemblance between these and the deep-ocean halite deposits.

Because Sozansky's studies of salt formations were restricted almost entirely to halite deposits found in ocean floors, he himself has tended to deny the reality of extensive evaporite deposition in ancient times. (Due to his unfamiliarity with such deposits, and his ill-informed statements about them, his works have not been well received among sedimentologists of the U. S., Canada, and Australia, where abundant cyclic, evaporative deposits of anhydrite, gypsum, calcium carbonate, and halite are found. Apparently the very restricted "climate" in which Soviet scientists are required to work has not allowed him to learn the actual nature of the continental, cyclic deposits of evaporites and the fundamental differences between them and the thick, ocean-floor halite deposits which he has studied.) Thus, it is very unfortunate that Morris has supposed that he can safely use the writings of Sozansky to support his notion that extensive evaporite deposits of various salts do not exist.¹

2. Precipitation of Evaporites in Relatively Deep Bodies of Water on the Continents

Another source which Morris used in his discussion of evaporites was a set of experiments performed by Omer B. Raup. The results of the experiments were reported in Raup (1970). The work of Raup in no way contradicts, or attempts to contradict, the necessity of intensive evaporation of the seawater by wind and sun beforethe layers of cyclic evaporite rock which are so well known could be formed. In his research report (1970) Raup repeatedly states that his experiments were an attempt to approximate the conditions which existed in ancient evaporite basinswhere extensive evaporativeconcentrations of seawater had already occurred. But Morris seems to have misunderstood the purpose, results, and most of the methods of the experiments, supposing that they were an attempt to demonstrate that layers of evaporites could be formed from seawater without time or opportunity for evaporation to take place.² The truth is that these were experiments made with marine brineswhich had been prepared in the laboratory. Raup (1970) explains, on pp. 2247 to 2251, that the experiments were performed with the use of 57 liters of normal seawater which were brought from the California coast and evaporated down to concentrated brine solutions. He then says, "The sea water brines were prepared by evaporation to eight stages of concentration: specific gravities of 1.146, 1.166, 1.183, 1.201, 1.219, 1.280, 1.313, and 1.326" (p. 2247).

It should be noted that the specific gravity of 1.146 represents a solution which was evaporated down to approximately 17% of the original seawater volume. (Normal seawater has a density of 1.026.) In his experiments Raup used somebrine solutions which were made from water, pure sodium chloride, and pure magnesium chloride, but all of these were of concentrations greater that 1.12 specific gravity. Thus, Raup's experiments were being made with concentrated brines of types and densities such as are formed in stagnant seas by natural evaporation—not with unconcentrated seawater or with waters obtained from hydrothermal sources.

In this research report Raup keeps pointing out that the results of the experiments support the principle of the formation of evaporite deposits by natural evaporation. The distinctive feature of his research was that it demonstrated that it is not necessary for evaporation of a body of water—such as a stagnant part of the Red Sea—to proceed allthe way down to the saturation point of sodium chloride, for example, (sp. gravity 1.219) in order to bring about precipitation of that salt, ifthe concentrated brine moves to other levels in the body of water which possess another type of brine.³

3. Organic Matter in Ancient Evaporite Deposits

A further basic error in this treatment of evaporites by Morris is his statement that there is "the complete absence of organic material in 'evaporites.' " (1974, p. 106). This is completely erroneous, and his inclusion of it in the chapter is unaccounted for. Probably Morris was again thinking only of the great halite deposits such as salt domes and some of the ocean-floor salt bodies. But there are large areas in the United States and Canada, as well as in other continents, that are underlain by ancient, cyclic evaporites which contain abundant and very obvious organic remains. There are hundreds of research reports by petroleum geologists which describe these cyclic deposits.

We want to examine evaporite deposits in some detail in this and the next chapter, not merely to demonstrate the failure of Morris to understand the great majority of them, but also to see what a decisive and positive evidencefor great age most of them are. In the next chapter we will consider a few of these large inland evaporite deposits at some length, but at this point we will briefly describe two areas in North America that are well known for their ancient evaporite strata which contain definite and obvious organic components.

(1) There are extensive deposits of thin-bedded anhydrite (calcium sulfate) in the Middle Devonian of western Canada. These evaporite layers underlie a large part of both Alberta and Saskatchewan, in Canada, and regularly contain thin, dark laminae* of organic matter alternating with the anhydrite laminae (Fuller and Porter, 1969, pp. 922- 25). This alternating of salt and organic laminations is typical of many of the evaporite formations found in the oil fields of the world. The reason that the organisms which produced the organic matter (mostly algae) could not thrive during the entireperiod of evaporite deposition is that each time the water became concentrated enough to begin precipitating the salt (calcium sulfate in this case), the algal growth was inhibited by the high concentration. The seawater has to be concentrated to slightly less than 20% of its original volume before precipitation of calcium sulfate (gypsum and anhydrite) can begin. Some species of algae are able to survive in saline waters of this concentration (Sloss, 1969, p. 779), but the large volume of growth necessary for producing a noticeable, dark organic layer in the anhydrite deposit can occur only at lesser concentrations. All evidence supports the assumption that these lesser concentrations existed during seasons when rains and other influx of water diluted the inland seas in which these evaporite deposits were formed. Many of the evaporite formations of North America, including the Middle Devonian of Alberta and Saskatchewan, have thicknesses of evaporite salts which contain some thousands of regularly alternating evaporite and organic laminae.

In most of these organic laminae it is impossible to distinguish the remains of the specific organisms which produced the organic substances. This is because the bottom waters of hypersaline* seas are nearly always anoxic, containing very little oxygen. When the algal cells, algal filaments, and other planktonic organisms sink to the bottom, anaerobic species of bacteria bring about a partial decomposition of the organisms. Since very few species of planktonic algae have mineralized cell walls of a kind which would survive the periods of decomposition, the cells are only occasionally identifiable in the organic laminae (compare paragraph 3 of Section 4, (b), below). This decomposition process has been observed and studied in great detail in several of the hypersaline lakes and seas of the world, and is explained in Kirkland and Evans (1981, pp. 187-88). The paper by Kirkland and Evans also gives a great deal of information on the intensity of algal growth (productivity) in the evaporite-producing hypersaline lakes and lagoons which they studied in various parts of the world. It also states the percentages of salinity at which certain algal species readily grow. The high productivity which is often found in hypersaline waters has led Kirkland and Evans, as well as other authors, to postulate that the large amount of algal growth in the ancient evaporative seas provided an appreciable part of the organic matter which was converted into petroleum to form the oil that is so often trapped beneath the evaporite layers. Another recent source which describes intense algal growth in a brine pool is Jacob Kushnir's "Formation and Early Diagenesis of Varved Evaporite Sediments in a Coastal Hypersaline Pool" (1981). In his detailed study of a hypersaline pool on the coast of the Red Sea at the southern tip of Sinai, Kushnir identified a series of annually produced, algal-gypsum couplet layers (laminae) extending chronologically from the time of his taking cores of the floor sediments, back at least 15 years. There are 15 easily identifiable couplets in the cores, showing an algal layer and a gypsum layer in each couplet (Fig. 3, p. 1195). Since Kushnir's studies extended over a period of several seasons he was able to observe that the algal growth, and layer of deposited algal remains, developed in the winter when the brine was not so concentrated; and then that the calcium sulfate—gypsum in this case—formed as a layer in the summer when the increased evaporation rate had further concentrated the brine (pp. 1194-95).

He also observed that the algal remains were identifiable in the younger laminae, but that in the organic laminae of the couplets in the deeper sediments the cell walls were no longer identifiable, because of further disintegration over the longer period of time. However, the dark, organic compounds remain in a preserved state. This seems to exactly correspond to what we find in the many ancient evaporite deposits which have organic laminae alternating with the calcium sulfate.

(2) One of the world's best-known, ancient evaporite formations which contains a large, laterally extensive, vertical sequence of laminated evaporites is the Castile Formation of west Texas and southeast New Mexico. This formation lies deeply buried throughout most of a 90- by 160-mile basin which contains a great number of oil wells, and includes in its thickness approximately 200,000 evaporite "couplet" laminations across most of the basin. (See Figure 6, and see "basin" in glossary.) These thin "couplets" (actually triplets) regularly contain a layer of calcium carbonate (CaCO₃), a layer of anhydrite (CaSO₄), and an organic layer, in each. (R. Y. Anderson, et al., 1972.) The layers are usually called either "microlayers" or "laminae" (singular "lamina"). The mean thickness per couplet was found to be 1.1 to 2.0 mm, depending on the depth from which the core being studied was taken, in the well.
 

Figure 6. Photographs of three vertical-column thin sections of the well cores used by Walter Dean in his studies of the Delaware basin. The strips of well core were ground thin enough for light to pass through for photographing. The light layers are anhydrite, and the dark layers calcite; thus many evaporitic couplets are seen in each column. Note the scale bar near the top, of length 10 millimeters. The slanting lines connecting the core sections identify the same couplet in two (or three) wells. The wells, designated as "Cowden 2," "Cowden 4," and "Phillips," are approximately 6.5 and 15 miles apart, respectively, in Culberson Co., Texas. From W. E. Dean, Jr., Petrologicand geochemical variations in the Permian Castile, varved anhydrite, Delaware basin, Texas and New Mexico,Ph.D. dissertation, University of New Mexico, 1967, 326 pp., Plate 3. (By permission of the author.)

Because of the presence of the calcium carbonate (calcite in this case) laminae of the "couplets," we are forced to conclude that the surface layer of the body of water which was precipitating the calcite and anhydrite was periodically restored to at least close to 50% of the volume and concentration of normal seawater—possibly even closer to normality. Then, during the season of high evaporation rate, the concentration again increased to where CaCO₃ precipitated out; and when the volume was further reduced to approximately 20% of that of normal seawater the CaSO₄ began to precipitate out. (The CaSO₄ probably precipitated as gypsum first and later was dehydrated to the anhydrite form.) (See p. 81, Table 1, in Wonderly, 1977, for details of the percentages of concentration at which the precipitation takes place.) It is evident that the organic lamination which each "couplet" usually contains consists mainly of the remains of the planktonic algae which grew prolifically during the time when the brine concentration at the surface of the body of water was low. This is in agreement with the fact that, throughout this great deposit of thinly laminated evaporites, the thicknesses of the alternating calcite and anhydrite laminae are in a proportion similar to thatof the dissolved CaCO₃ and CaSO₄ in seawater. (Seawater normally contains a much smaller percentage of CaCO₃ than of CaSO₄—see Wonderly, 1977, pp. 101-03 for details.) Thus the layering of the Castile Formation provides us with a physical record of the periodic—probably annual—changes of seawater concentration and the rise and fall of the organic productivity in each period. It is important also to note that the high degree of purity and distinctness of the laminae over broad geographic areas completely rules out the possibility that the deposition occurred during a period of water turbulence such as evidently existed even in the late stages of the Biblical Flood. And obviously the drying up of the waters of the Flood, as described in Genesis 8:13-14, could not have produced anything like the repetition of laminations which we find in the Castile Formation.

Walter Dean made a very detailed study of the couplet layers of this Castile Formation throughout almost the entire basin (Dean, 1967). He actually measured and recorded the thicknesses of the rnicrolayers in 12,800 "couplets" which are vertically sequential in the 200,000 couplet series of the Castile Formation, in Texas and New Mexico (Dean, 1967, pp. 213-87). The measuring of these thicknesses in the well cores from different parts of the Castile Formation (which fills the ancient evaporative basin) made it possible to check to see how far individual laminations could be traced across the basin. The result was that several sets of laminations (e.g., those shown in Fig. 6 of this book) were distinctly correlated for a distance of 60 km (37 miles). Thus Dean states that "results of this investigation indicated that individual laminae within the Castile Formation could be traced with remarkable uniformity for a distance of at least 60 km." (1967, p. 15; pp. 73-75 explain the procedures of these correlations). Very uniform thicknesses of the laminae of the "couplets," as well as a consistency in the chemical content and in the organic matter, had been preserved across this 60 km distance. A report of the extensive chemical tests which were made on all three types of laminae in the "couplets" is given in the dissertation (1967, pp. 29-60). Correlative work done later in this same basin traced individual laminae, and also beds of nodular, laminated anhydrite, for distances up to 113 km (Anderson, et al., 1972, pp. 61, 70; Handford, et al., 1982, p. 325).

Dean's observations concerning the relationships between the organic layer and the two mineral layers of the "couplets" are very significant. He says:

A microcrystalline calcite lamina is usually followed by one or more very thin organic laminae separated by carbonate-free sulfate laminae which frequently contain "flakes" of organic matter concentrated at the top of the sulfate lamina. These organic "flakes" often form a lacy network immediately below a microcrystalline calcite lamina. (Dean, 1967, p. 37)

Thus we are forced to conclude that the layers of the Castile Formation were formed naturally by evaporation and periodic algal growth. Morris has made his denials of the reality of evaporative deposition (Morris, 1974) without knowing or understanding the nature of the evaporite deposits or of the processes of evaporite deposition. Unfortunately, there is no change in this in the new, 1985 edition. (The section on evaporites is pp. 105-07 of both the 1974 and the 1985 editions.)

Sometimes there is a question of why small, hard-skeleton fossils are so infrequently found inthe organic laminae of evaporite deposits. It must be remembered that very few of the marine animals which produce such skeletons are able to live in hypersaline waters. It is mainly the algae which have this capacity; and even they, as pointed out above, come practically to a standstill in their growth during parts of the year when the water has become sufficiently concentrated to precipitate gypsum or anhydrite.

However, there are many laminated anhydrite formations which contain identifiable fossils in black shale layers which are interbedded with the sets of organic and evaporite laminae. For example, in the Paradox Formation in Utah, fossilized conodonts, brachiopods, and plant remains are found in the black shale layers which alternate with sets of evaporite and organic laminae (Duff, 1967, p. 204). (The shale layers obviously were formed during the longer periods when the water in the evaporative basin was less saline, allowing these organisms to grow.)

¹All that Morris says about Sozansky's work in his Science, Scnpture, and the Young Earth(1983, pp. 10-11) is a further demonstration of the fact that he very seriously misinterpreted Sozansky's writings and thus concluded that all of the world's evaporite formations are very similar to the halite deposits in the floor of the Atlantic Ocean.

²Misunderstandings of this type are usually due to failure to read the research report carefully, or to mere dependence upon the abstract and conclusion of the paper. This must certainly have been the case here, because Raup's report is very clearly written.

³For additional information which complements Raup's work see Sloss (1969); Schmalz (1969); and Davies and Ludlam (1973), pp. 3527-46.

⁴For example, occasionally a couplet was found to have the organic lamina on top of the calcite. This apparently means either that, in that particular year, conditions were unusually favorable, so that the algal growth could continue until the calcite had precipitated out; or that the percentage of co2 in the surface layer of water dropped so low, due to the algae's use of the CO2. that the precipitation of CaCO3 was triggered earlier than usual (Dean, 1967, p. 148).