Spring 1991, No. 13
THE SANTANA FORMATION
In past years unusual fossil fish from Brazil came to the attention of the Geoscience Research Institute staff. Recent scientific research on these fossils (Martill, 1988) also stimulated our interest and led us to include this fossil location in the itinerary of a research trip to South America in early 1991.
The Santana Formation, in which the fossil fish are found, is located in the southern part of Ceara Province in Northeast Brazil. These fossils first came to the attention of the world in 1828 when two European travelers briefly mentioned them and included one illustration in their publication. In 1841 George Gardner described a collection he had obtained in the Reports of the British Association for the Advancement of Science. Louis Agassiz (famous American zoologist) did taxonomic studies in 1841 and 1844 on Gardner's collection. E. D. Cope, Smith Woodward, and David Starr Jordan, well-known ichthyologists, also studied the Santana fish in 1871, 1887, and 1908 respectively. More recently there has been a revival of interest by paleontologists from several countries.
The fish fossils are usually contained in concretions and often still retain their original three-dimensional form (Fig. 1). The fossils in a concretion may range from part of one fish to several complete fish. Occasionally other organisms also are seen in these concretions.
Fig. 1: Four fish from the Santana Formation that still maintain their three-dimensional form.
This Cretaceous bed is exposed around the slopes of the Chapada do Araripe, an irregular plateau with dimensions about 115 miles long east-west and 30 miles wide north-south. The plateau is about 1000 ft above the surrounding country at an elevation between 1800 and 2700 ft (Fig. 2).
Fig. 2: The Araripe Plateau from which the concretions containing fossil fish are eroding. The concretions are scattered over the slopes closer to the top of the plateau.
The large variety of fishes and other organisms are a mixture of oceanic and fresh-water species. Along with many
modern species of true fishes are several species of extinct Mesozoic fishes and one bat fish
(Rhinobatus). The true fishes come from benthic, semi-benthic, pelagic, littoral, and estuarine environments. They also include surface feeders, microphagous planktonic feeders, small fish eaters, and two coelacanth fish, one a new genus. Coelacanths are generally considered to be deep sea fish. Fossil coelacanth fish also have been uncovered in West Africa (Martill, 1988).
Jordan and Branner (1908) regarded a specimen of Calamoplurus cylindricus from Brazil as the most perfect fossil fish they had ever seen. Color stiff remained on the scales and even the eyeballs were preserved. In the field, we opened one concretion with a fish head. The eyeballs of this specimen still maintained the spherical form even though now petrified (Fig. 3).
Fig. 3: A concretion containing a fish head.
Fossil Aspidorhyncus comptoni Agassiz are among the most abundant fossil fish. They are slender appressed fish with a pointed snout and with unusual slender scales along the sides. If only part of the body of the fish is exposed, one might think he were looking at a snake with its ventral scales (Fig. 4).
Fig. 4: Two well-preserved fish, one strongly coiled, within one concretion.
Most of the Santana fossil fish still have their scales. When a fish dies, one of the first indications of decay is the loss of scales which can commence a few hours after death. The full armament of scales on these fossil fish and the absence of isolated scales in the surrounding sediments are strong indications of extreme rapidity of burial and preservation.
In addition to fish, a surprising array of other fossil organisms is present. A list of invertebrates is as follows:
Besides a wide variety of fishes and a few plants, the following vertebrates have been collected:
An examination of these fists immediately indicates the mixed nature of the fauna. For instance, some of the marine fishes are embedded in calcareous shale in which also are located hundreds of tiny fresh-water ostracods. The marine echinoids mentioned in the invertebrate fist above were found in sediments of a fresh-water sequence.
The ostracods are mostly adults of only a few species. This lack of variety is suggestive of fresh-water environments. Marine environments support a large suite of species. The valves of these minute animals (not much larger than a pin head) often are closed, suggesting rapid burial while the animals were alive. The preservation of these ostracods and the copepods mentioned below allowed us to see minute details of appendages, mouth-parts, reproductive organs, eggs, etc. All these parts are covered with submicroscopic phosphatic crystals (Bate, 1972; Creasey and Patterson, 1972).
The copepods were parasites on two fossil Cladocyclus fish skulls. The oldest copepod parasites previously reported as fossils are Miocene said to be 10 to 20 millions of years old. These parasites of Cretaceous fish extend the range back to 100 million years based on the standard geological time scale, yet they are fully adapted to a parasitic existence on fish. These fish containing marine copepod parasites are buried with freshwater ostracods. Parasitic copepods are a highly specialized group with bizarre morphology. Their presence in Cretaceous fish means that the evolution of the group would have had to be completed before the Cretaceous. This is another example of homeostasis (stability) of a specific group even when the geologic range is greatly extended.
Recent discovery of a fossil crocodile skull from the Republic of Niger in west central Africa suggests, along with numerous other fines of evidence, the juxtaposition of Brazil with West Africa in the Cretaceous (as does also the coelacanth fish mentioned earlier) (Buffetaut and Taquet, 1972). It has been identified as Araripesuchus, the same genus as those from the Santana Formation.
Ten species of pterosaurs (flying reptiles) have been identified. The bones are uncrushed and well preserved, occasionally even articulated. In one unusual case, part of the wing membrane was preserved (Unwin, 1988).
The hardening of the concretions must have started before or during early decomposition of the fish. The bones are little altered. The body fluids of the animals probably contributed to the hardening by seeping into the sediments directly surrounding the fish. In many instances, phosphate (cryptocrystalline francolite) replacement of tissues (especially muscle tissues) prevented decay and preserved the three-dimensional shape of the fish.
Soon after the crystallization of the phosphate came the pyrite. Ovoids such as body cavities and swim bladders are lined with pyrite and calcite, the calcite being the innermost and the last to crystallize. Gas produced before the sediments hardened helped to maintain the three-dimensional features of the fish. In some instances gas bubbles forced their way through the body wall and pushed several scales out into the sediments to produce a small eruption-like crater (Martill, 1988). Release of gas pressure from within body cavities might be expected to allow the fish carcasses to collapse. In most instances this did not happen. Usually sediments and fish tissues hardened so rapidly that the fish are still "in the round."
Under the electron microscope the lamellae of the gills can be seen uncollapsed. These structures will collapse in one to three hours when removed from fresh fish. Greater magnification even shows the individual cells of the lamellae still turgid. Such a condition indicates that the preservation probably occurred within one hour (Martill, 1989)! Beautiful preservation in such abundance has not been found anywhere else in the world.
Collection of these famous fossils is done by local farmers. The concretions are scattered over the slopes along the edges of the plateau. Trenches and pits are dug to give access to more of them. We spent several fascinating hours cracking open concretions. Of the many excellent fossils we kept only a few of the best because of the weight limitations imposed by air travel. Those that we discarded would normally be classed as marvelous fossils!
The museum in the small town of Santana contains an excellent representation of fossils from this formation. Insects of unusual detail and variety, leaves and stems of plants, fish of great size and detail, flying reptile skeletons, possible dinosaur bones, invertebrates, and other miscellaneous fossils, emphasize the heterogeneous mixture from these beds.
At one location several miles beyond automobile access, we dickered with a local peasant for the purchase of some especially beautiful fish specimens. In his yard was a pile of discards that would have been considered valuable fossils elsewhere. In a small shed with thatched roof, fish fossils were piled up awaiting purchase by a middleman who would pass them on to curio stores and rock shops. By the time these fish reach Europe and North America, they will command a substantial price.
The sequence from top to bottom for the Santana Formation is as follows: Below thick deposits of sandstone and limestone that cap the plateau he the fossil-bearing beds. Directly below a thin layer of marine invertebrates fossils consisting mainly of gastropods lie the fish fossil concretions. Below the fish fossils is a 90 ft bed of evaporite (gypsum). Under the gypsum a layer of fine-grained calcareous shale that is being quarried for building stone, contains insects, small fish, and plant fossils (Fig. 5). Below these laminated limestones scattered remains of dinosaurs and petrified trees have been collected.
There is much similarity of the laminated calcareous beds with the Green River Shales of Wyoming. Martill (1989) also compares this section of the Santana with the famous German Solnhofen limestones from which several Archaeopteryx specimens have been collected (see book review, this issue). The nature of the laminated limestones is similar, and both are quarried for building stones. Fossil preservation in both is remarkable, with that in Brazil the most spectacular. Preservation of soft tissue is less common in the Solnhofen. A variety of habitats represented by the fossils (marine, limnetic, terrestrial, etc.) is a feature of both areas. The kinds of organisms are in good agreement. For instance dragonflies, cockroaches, beetles, wasps, and flies among these listed for the Solnhofen are also found in the Santana. Vertebrates especially noticeable in both areas are small sharks, ratfish, rays, turtles, ichthyosaurs, crocodiles, and pterosaurs. The most notable differences are the presence of an evaporite bed (gypsum) and the lower abundance of marine invertebrates in the Santana Formation. As yet no birds have been found in the Santana limestones but this area, although extensive, has had little attention from paleontologists.
Fig. 5: A small fish and a plant preserved together on the same slab of calcareous limestone.
What conditions were necessary to bring about so remarkable a fossil deposit as the Santana? Much additional study is required but some tentative conclusions can be drawn.
The Chapada do Araripe is probably not the full extent of the original Santana Formation.
Many miles beyond the edges of this plateau, patches or pockets of Santana are found. The broad range of this formation, the evidences of rapid sedimentation and preservation, the quick cementation of the nodules with enclosed fish fossils, and the mixture of fresh-water and marine organisms, has been surprising to paleontologists and geologists who have tried without much success to encompass all these requirements in an estuarine environment that was stirred up by a catastrophic tsunami. The resulting sediments could have been a mixture of marine, brackish, and fresh-water sediments, and the fauna caught and buried also could have come from these three major types of environments. Yet the absence of typical bay and estuary invertebrate organisms is a problem for this model.
The evaporite layer and the fine-grained flat-lying shales could suggest quiet conditions and the passage of time. However, water of sufficient depth can allow for quiet sedimentation even when a major storm is ravaging the surface. Most evaporites, contrary to the name, probably were not produced gradually by long continued evaporation. Evaporites can readily be transported. It is most unlikely that the fish fixed within the concretions were originally living normally in water directly above a salt deposit (gypsum). Some of the concretions he directly upon the gypsum. Also there does not seem to be a transition from the underlying shale sheets to the massive evaporite as would be expected if the origin of the gypsum were truly by evaporation.
The unnatural mixture and the rapid stratigraphic shifts of fauna seem to require catastrophic water transport into the area. The large geographic extent precludes a local event. Creationists suggest that a world-wide flood could produce results as seen in the Santana Formation and is a better explanatory model.
SCIENCE NEWS NOTES
The Mima Mound Mystery Mastered (Maybe)
In a number of locations in North America and elsewhere, the ground is covered with mounds of sediment (Mima mounds) that range in diameter from 2.5-15
m and up to 3 m in height. The genesis of these mounds (also called prairie mounds, or pimple mounds) has been a mystery and the subject of controversy and discussion for over 100 years. These hemispherical to ellipsoidal mounds may be composed of unconsolidated loess, silt, sand, or even gravel. In the troughs surrounding the mounds, one finds coarse sediments such as gravel, pebbles and rubble. The type locality is Mima Prairie south of Olympia, Washington, but they are abundant in the basalt scablands of Eastern Washington, the Central Valley of California, and the Gulf Coastal Plains, as well as other areas.
Most attempts to explain this geological puzzle have centered around depositional, erosional, periglacial, and biological causes. Tufts of grass or vegetation are said to have collected wind-blown silt and loess, increasing the size and height of the mound each year. The erosional hypothesis holds, conversely, that wind or water removed sediments from intermound areas. Those favoring a periglacial process propose that freezing and thawing have brought about the segregation and accumulation of sediments needed to produce fine-grained mounds surrounded by coarse materials. There has even been a suggestion that the mounds are the result of burrow-making by ground squirrels or gophers.
A new hypothesis has been presented by Berg (1990), who proposes that these piles of dirt are produced by the seismic shaking of sediments. In most cases, the mounds are located in a thin layer of unconsolidated soil atop a flat firm surface of hardpan, gravel, or basalt. Mounds can be produced experimentally on a small scale by tapping a sheet of plywood on which a thin layer of loess has been sprinkled. Waves of motion cause a sorting of the fine and coarse fractions of the sediments into fine-grained mounds and coarse-grained troughs similar to the Mima mounds.
If this theory is correct, these sediment piles are evidence of seismic activity on a grand scale in the past. Such earthquake activity is expected during the time of crustal adjustments and major volcanic upheavals that occurred during early post-flood times.
The eruption of Mount St. Helens, in 1980, was an exceptional event for Americans who live in the contiguous 48 states. No volcanic eruption has occurred here within the lifetimes of most of the inhabitants.
Although lives were lost and property damage resulted from this eruption, all was not bad. No volcano has been as well studied as this one. Danger from great landslides such as happened on the north face of the mountain on May 18 the greatest rock and land slide witnessed by modern man is now appreciated. Three major rockfalls that followed in rapid succession deposited great quantities of material into the upper Toutle River Valley and produced a debris flow that moved 15 miles down the valley.
A unique feature of this deposit is its hummocky terrain. Surprisingly the debris from the mountain was not mixed during its movement along the valley floor. The surface of the flow is uneven with peaks and pinnacles. This unexpected surface topography is characteristic and has led to the identification of similar major rockslides in other areas that had not been recognized.
One of the more spectacular of these areas is the odd terrain consisting of numerous conical domes located on the northwest side of Mount Shasta, California. These small hills had been variously interpreted but the favored opinion was that they were the result of small volcanic eruptions even though craters or eruptive centers were not obvious. The true interpretation came quickly after the eruption of Mount St. Helens. This area near Mount Shasta was clearly the result of a major prehistoric landslide. The slide was so large and the resulting hummocky ground was on such a large scale that the cause of this landscape had not been recognized until a similar landscape was produced by the smaller landslide from Mount St. Helens. Travelers on Interstate 5 can see part of this unusual topography where the freeway passes northwest of Mt. Shasta.
The Mississippi River Delta
The delta of the Mississippi River is much smaller than would be expected if the river had been flowing for hundreds of thousands or millions of years. In fact, the present rate of sediment discharge would have filled the Gulf in approximately 10 million years, but the presence of a deep and open gulf speaks against the passage of millions of years since the establishment of the drainage of the Mississippi River. Past calculations, based on the present rate of sediment being transported down the river into the Gulf of Mexico, indicated that the delta is only 4000-5000 years old.
More recent surveys and drillings on the bottom of the Gulf of Mexico are said to have added substantially to estimates of the total amount of sediment brought into the Gulf by the Mississippi River in the past. The 4000-5000 years for the age of the Mississippi delta fits well with biblical chronology, but the recently determined increase in delta sediments has pushed back substantially the time calculated for the beginning of Mississippi River deposition into the Gulf.
Another factor needs to be included before any final conclusions can be drawn about the age of the delta. Conditions following the Genesis flood appeared to have favored the establishment of large glaciers covering portions of continents. Much water was locked up as ice in glaciers in Canada, Northern United States, Northern Europe, and other locations. When glaciers began to recede, water swelled the rivers and increased the erosion of newly exposed, unvegetated land. The deposition of sediments at the mouth of the Mississippi River was then more rapid than now. Research along the Atlantic Coast on the sediments from the mouth of the Hudson River off New York to Cape Hatteras, North Carolina, has revealed that much of it came from the drainage of the Hudson River. Today the Hudson River contributes little sediment to areas so far to the south. The sediment discharge rate of the Hudson then is thought to have been as much or more than that of the Amazon or Mississippi Rivers today.1 If the Hudson River was so much larger then, what size was the Mississippi River at that time? Based on oversized river channels as compared to the sizes of the present rivers, most rivers have been larger in the past. It is not difficult to visualize that the rate of sedimentation for the Mississippi River during melt-back of continental glaciers was much greater than present rates. Similar to the Hudson River, the Mississippi had its sources in areas along the edges of the continental glaciers and in the heavily glaciated mountains of the Rocky Mountain states drained by the Missouri River.
The correction factor required by the increased sedimentation rate during the retreat of glaciation may not be determinable, but a 4000-5000 years span for the growth of the Mississippi delta may well be close to the correct figure. There also is controversy concerning the true source of these newly discovered sediments farther out in the Gulf. Some researchers think they may have been derived from slumps and turbidity currents not directly associated with the Mississippi and its delta.
CLAUSEN IN RUSSIA
Ben Clausen spent three weeks in Russia as a guest of the Academy of Sciences of the USSR during the month of March. Lectures on nuclear structure were given and visits were made to accelerators at the Joint Institute of Nuclear Research at Dubna, the Moscow Meson Factory under construction at Troizk, and the Leningrad Nuclear Physics Institute at Gatchina. He spent time assisting in the computer simulation of particle interaction and decay in a pion spectrometer at Dubna, helped install a data analysis computer system for nuclear physics experiments at Troizk, and visited the proton beam fines at Gatchina that are used for cancer therapy and for producing exotic short-lived nuclei that rapidly undergo radioactive decay. An openness to religion was evident by suggestions for future lectures on religion and science and by questions concerning his church and beliefs. Two were very pleased to receive Bibles and attended part of a Sabbath church service. The invitation to visit Russia came as the result of collaboration with two Russian scientists on an experiment at Los Alamos in August, 1990. The scientists of the Academy of Sciences went out of their way to make the visit pleasant and informative.
GEOSCIENCE VISITS COSTA RICA
The Geoscience Research Institute conducted a three-day creation seminar October 5-7, 1990 on the campus of the Adventist University of Central America (Universidad Adventista de Centro Americana), in Costa Rica. The seminar was led by Drs. David Rhys, Clyde Webster and Jim Gibson. More than 100 faculty and students attended the weekend seminar. While at the university, the GRI members also met with the university faculty to discuss the research program at the university, which has recently achieved full government recognition. During their time in Costa Rica, the GRI team was able to visit some of the many volcanoes that make up the backbone of the country and form the link connecting North America and South America.
MAY I ASK A QUESTION?
Did dinosaurs live after the Flood?
A few reports of dinosaurs depicted in petroglyphs, on ancient pottery, etc., are sometimes used to suggest that dinosaurs lived after the Genesis flood. These evidences are not convincing. The figures are questionable they could be representations of turtles or other animals that give the superficial appearance of dinosaurs.
The recent discovery of dinosaur eggs and nests in Montana, Alberta, and elsewhere could be interpreted to mean that the animals which laid the eggs lived in a normal situation during the Cretaceous. Sediments of this period are usually classified by creationists as late Flood deposits. Nest building and egg laying are usually not activities one would expect during a world-wide catastrophe. Yet there are aspects that indicate unusual conditions. The nests and eggs were obviously buried quickly. Embryos and hatchlings are found buried beside or near the eggs. Three or more levels of these nest sites, separated by a few feet of water-laid mud and directly above each other, require repeated flooding and burial. Furthermore, in some cases thousands of adults (Horner, 1988) were buried in deposits stratigraphically and geographically close to the eggs.
There is reason to believe that some dinosaurs had herding instincts. A breeding time that brought all the pregnant females to egg laying at about the same time is likely also. If breeding occurred near the beginning of the Genesis flood, egg-laying time would find the dinosaurs struggling with a major catastrophe. The gravid females would be forced to lay their eggs on whatever ground was exposed, even ground subjected to repeated overflow of water and mud deposition.
The dinosaurs disappeared suddenly at the end of the Cretaceous. A few suggestions of dinosaur remains in the Cenozoic Paleocene, if true, are not a problem for creationists who would consider the Paleocene also to be late Flood deposits. Many theories have been proposed for this abrupt extinction as noted by this statement from a paleontology textbook (Beerbauer, 1960):
What happened? Change of temperature? Change in the plants? Blasts of heat from a meteor; mammals eating dinosaur eggs; hyperpituitarism; change in oxygen concentration; over-specialization and senility of the dinosaur stalk; and so on ... and on ... and on? Some of these explanations seem absurd, but this illustrates the desperate straits into which paleontologists have been pushed by the mysterious extinction of the dinosaurs.
Extinction by a world-wide flood is as reasonable an explanation as any theory, even though one does not often find this idea in the scientific literature. Charles Camp (1930), who spent many years hunting and excavating dinosaurs, made the following comments:
In many instances it seems that skulls and skeletons sank rapidly in oozy ground which later became subjected to great pressure from superimposed sediments resulting in flattening and crushing of the bones.... Occurrences of fossil wood and bone in the Chink are so distributed that they might be taken to indicate periods of cataclysmic extinction. From the presence of great volcanic ash deposits and the frequent occurrence of pure charcoal lumps and charcoal encrusted logs in these deposits, it would seem at first thought that the bone beds and fossil forest may be due to sudden destruction of life by volcanic outbursts, accompanied by fire and flood.
The current popular theory is that an extraterrestrial body hit the earth, produced a dust cloud that blotted out the sun for months, and brought about the extinction of certain plants and animals including dinosaurs. If such an event actually happened, we would consider it to be part of the complex of activities associated with the flood catastrophe.
Seventh-day Adventists customarily place the disappearance of the dinosaurs in the Genesis flood. Part of the basis for this position are statements appearing in Spiritual Gifts, vol. 3, p. 92, and vol. 4, p. 12 1. The latter quotation is as follows: "There was a class of very large animals which perished at the flood. God knew that the strength of man would decrease and these mammoth animals could not be controlled by feeble man."
Barthel, K. W., N. H. M. Swinburne, and S. Conway Morris. 1990. Solnhofen: A study in Mesozoic paleontology. Cambridge University Press, New York. 236 pp.
Approximately 100 km north of Munich, Germany, are several valley basins containing pure thinly laminated Jurassic limestones that have been mined for centuries as building stone. Occasionally, well-preserved fossils are seen as the thin beds of limestone are pried apart and prepared for building stone. Among the large variety of organisms found in the rocks were several specimens of
Archaeopteryx, which has been widely acclaimed as a connecting link between reptiles and birds. The Solnhofen limestones will no doubt continue to be an area of high interest to paleontologists, even though
Archaeopteryx is losing its significance because modern-type bird remains are being found in "older" rocks elsewhere. The large number of fossil organisms collected over the years from the Solnhofen, include marine invertebrates (king crabs, molluscs including cephalopods, jellyfish, starfish, worms, and many others); terrestrial invertebrates (dragonflies, cockroaches, beetles, wasps, flies, etc.); vertebrates (fish, sharks, turtles, marine reptiles, crocodiles, dinosaurs, etc.); and plants (algae, seed ferns, and conifers including
ginkgoes and cycad-like small trees).
The Solnhofen beds are thought to have formed slowly in basins not well connected to the open ocean. Periodically, storms washed or blew the sea and terrestrial organisms over the barriers into the basins where they quickly died in the anoxic bottom waters. In such an environment, decay and disintegration were presumably delayed until burial fixed the organisms permanently in the sediments. Although the thinly laminated limestones would seem to preclude heavy water action, their low organic carbon content does not appear to suggest anoxic bottom waters. The well-preserved plants and animals from both land and sea argue against the loss by decay and oxidation of planktonic and organic debris that normally would be expected to have settled from the warm surface waters during significant lapse of time between the deposition of successive sheets of lime.
Jurassic and Cretaceous beds are considered by most creationists to have been deposited during the termination of the Genesis Flood. A better explanation than that given by Barthel, et al., for these unusual fossil sites is the sinking of a variety of storm transported organisms into deeper quiet waters below wave base. The broad geographical areas involved and the unusual variety of organisms suggest a major catastrophe such as a world-wide flood.
Staff members of the Geoscience Research Institute had the opportunity to visit the Araripe Plateau in Northeast Brazil, the location of the remarkably preserved fish of the Cretaceous Santana Formation (see lead article). Below the concretions containing the fish, laminated limestones display an array of well-preserved fossils. These thinly bedded limestones are sometimes referred to as the Brazilian "Solnhofen." The authors of Solnhofen: A study in Mesozoic Paleontology make comparisons with several other areas of similar lithology and paleontology, but they do not include this Brazilian location, probably because it is not well known.
Spring 1991, No. 13
Editor - Harold G. Coffin
Associate Editor - Katherine Ching
Subscription requests, correspondence, and notices of change of address should be sent to: Geoscience Reports, Geoscience Research Institute, Loma Linda University, Loma Linda, CA 92350.
Geoscience Reports is a newsletter published by the Geoscience Research Institute to present current happenings at the Institute as well as articles of general interest which deal with creation/evolution issues for secondary-school and college science classes. The views expressed are those of the authors and not necessarily those of the Institute.
Staff of the Institute are Ariel A. Roth - Director, Katherine Ching, Ben L. Clausen, Harold G. Coffin, L. Jim Gibson, and Clyde L. Webster.
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