Coping with Difficult, Unanswered, and Unanswerable Questions

Difficult, unanswered, and unanswerable questions are often catalysts for paradigm shifts in technology, medicine, and in personal and community value systems.

Challenging questions important to Christian value systems are often about origins, evolution, pain and suffering, age of the earth, and various creation scenarios. Christian education has a responsibility to help individuals learn how to honestly cope with difficult questions in ways that fortify their trust in the biblical worldview. Sometimes, this means learning that the answer to a question may not exist, may exist while being currently unavailable, or that the question may be considered in alternative ways.

A Difficult Question is one that has a tentative answer and might later be determined to be Unanswerable or have an answer different from what has been accepted.

An Unanswered Question as yet has no proposed answer, but we think we can eventually discover an answer.

An Unanswerable Question is one for which we have no way to obtain information/data for formulating an answer.

Some Answers Can Wait

There are profound messages in the story of Job. Job wanted to question God about many things that were happening. God agreed to let this happen but first he posed questions to Job. Job where were you when I did this? Explain how I did this? And, Job had no answers and accepted a relationship that transcended getting all the answers. There were things behind the scenes that Job didn’t understand. Job eventually expresses his commitment to serving God even if God choose to slay him. Job’s relation with God was a faith-based experience that transcended any Difficult, Unanswered, and Unanswerable Questions posed by his tormentors or by God.

 Recognizing that some questions are not answerable can help us cope with our own questions, and lead us to trust the information given us by a loving and trustworthy God.

 – The finite will never completely understand the infinite. –

Robert D. Moon Jr. PhD

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Alpine ophiolites: Remnants of a lost ocean

In 1813, French geologist Alexandre Brongniart published a paper on the mineralogical classification of rocks[1] where he introduced the new name “ophiolite” for a suite of dark rocks rich in the mineral serpentine. The name was coined from the Greek words for “snake” and “rock,” which seemed fitting, given the smooth dark green appearance of ophiolites, vaguely reminiscent of snake-skin (Fig. 1).


Fig. 1: Close-up view of serpentinite (a component of ophiolitic rocks). Coin for scale is 1 cm in size. Totalp ophiolitic nappe, Parsennfurga, Switzerland.

European geologists throughout the 19th and early 20th century were relatively well acquainted with these dark rocks, first identified in several parts of the Apenninic and Alpine mountain chains but also occurring in other regions of the world. Ophiolites were generally interpreted as igneous rocks, forming from the solidification and differentiation of magma or from volcanic effusions.

While studying ophiolites in the early 1900s, German geologist Gustav Steinmann made some important observations that contributed to a better understanding of the origin of these rocks. Steinmann noticed that ophiolites were consistently in contact with layered strata made of limestone, clay, and chert, a silica-rich rock.[2] Sediments of similar composition (lime, clay, and silica ooze) had been recently retrieved from the deep seafloor, during the earliest oceanographic expeditions. Steinmann was aware of this, and he became convinced that ophiolites and the associated sediments must have formed on the deep ocean floor.

If this was true, however, why were rocks from the deep ocean floor occurring several kilometers above sea level in the middle of the Alps? This was puzzling because, at the time, continents and oceans were thought to have remained in a fixed position since their original formation. At the most, it was believed, only continents’ edges could fold to form a narrow oceanic depression, called “geosyncline”. Perhaps, alpine ophiolites were remnants of a geosyncline separating Africa from Europe (Fig. 2). Developing this idea, the Swiss geologist Émile Argand was the first to suggest that a large collision between the drifting continents of Africa and Eurasia had trapped and uplifted the deep rocks of the intervening geosyncline,[3] a model that became a clear precursor to the modern theory of plate tectonics.


Fig. 2: An Illustration of the geoscyncline separating Europe (left) from Africa (right). Ophiolites are represented as black lensoidal instrusions of magma in the geosyncline. Fiigure published in 1924, in the book of R. Staub, “Bou der Alpen.”

However, It would take 40 more years to develop a fuller understanding of the riddle of Alpine ophiolites. In the 1960s, a wealth of new information from the study of oceanic floors revealed that, in the Earth’s past, oceans had been dynamically created instead of being fixed and permanent.[4] It was discovered that the composition and structure of the oceanic crust was very similar to what seen in ophiolitic complexes.[5] The notion of geosynclines at the edges of continents was abandoned and replaced with the concept of plate margins at zones of oceanic subduction and seafloor spreading. Eventually, it became clear that ophiolites were not magmatic intrusions localized in a geosyncline but true slices of oceanic crust trapped in powerful collisions of tectonic plates.

The ophiolites found among the alpine peaks bear witness to the tortuous path of discovery and dynamic development of scientific concepts. They also represent a tangible record of mighty forces being at work in the past. In the pages of Scripture, we find an account of the Earth’s surface being affected by God’s powerful action at the creation and at the flood. Even if revelation does not address the subject of ophiolites, experiencing the gigantic plate motions revealed by these rocks generate a distinct impression that an unfathomable power has been active in the history of our planet and will be active again (2 Pt 3:5-7).

Suggestions for further reading:

Bernoulli, D., & Jenkyns, H. C. (2009). Ancient oceans and continental margins of the Alpine‐Mediterranean Tethys: Deciphering clues from Mesozoic pelagic sediments and ophiolites. Sedimentology, v. 56, 149-190.

Moores, E. M. (2003). A personal history of the ophiolite concept, in Dilek, Y., and Newcomb, S., eds., Ophiolite concept and the evolution of geological thought: Boulder, CO, Geological Society of America Special Paper 373, 17-29.

[1] Brongniart, A. (1813). Essai de classification minéralogique des roches mélangées, Journal des Mines, v. XXXIV, 5-48.

[2] Steinmann, G. (2003). Die ophiolithischen Zonen in den mediterranen Kettengebirgen (The ophiolitic zones in the Mediterranean mountain chains). Bernoulli, D., & Friedman, G. M., translators, in Dilek, Y., and Newcomb, S., eds., Ophiolite concept and the evolution of geological thought: Boulder, CO, Geological Society of America Special Paper 373, 77-91.

[3] Argand, E. (1916). Sur l’arc des Alpes occidentales. Eclogae Geologicae Helveticae, v.14, 145-191; Argand, E. (1924). Des Alpes et de l’Afrique. Bulletin de la Societe vaudoise des Sciences naturelles, v. 55, 233–236.

[4] Hess, H. H. (1962). History of Ocean Basins, In Engel, A.E.J., James, H.L., & Leonard, B.F., eds., Petrologic Studies: A Volume to Honor A.F. Buddington: New York, Geological Society of America, 599-620.

[5] Dietz, Robert S. (1963). Alpine serpentines as oceanic rind fragments. Geological Society of America Bulletin, v. 74, 947-952.


Ronny Nalin, PhD

Geoscience Research Institute

Posted in Geology, Philosophical and Historical Perspectives, Plate Tectonics | Tagged , , , , , , , | 1 Comment

“Living with the Exceptional”

There is one small molecule that makes our world unique and special. What is it? Water! Sure, other planets and moons in our solar system may have (or had) water and even more than Earth, but it is rare to find liquid water on the surface of a planet.(Kramer 2015, Wenz 2015)  Let’s consider one of water’s well studied properties: density. The density of pure water can be precisely known to five decimal places as a function of temperature between 0 and 100 oC.(Dean 1999)


Water ice cubeWater’s solid phase has a density that is less than the liquid phase. This is very normal to us since this is what makes ice cubes float! However, there are important chemical trends to understand that most materials go through as they transition from solid to liquid to gas phases.   The typical density relationship between solid to liquid to gas is a fairly consistent decrease. Most substances show about a 1.2x (20%) decrease in density going from the solid to liquid phase with an additional 800x (80000%) decrease in density going from a liquid to a gas.(Dean 1999, Lide 2003)  This is easily explained by showing that the intermolecular distances increase with rising temperature. The expansion results from an increase in kinetic energy of the particles which overcomes the attractive intermolecular forces holding the shape and structure characteristic of each phase. This explanation works for most materials, except water and a few elements.

H2O density graphI know of eight materials that exhibit an unusual density change going from a liquid to a solid in that the interatomic distance increases in the solid phase, i.e. the solid phase is less dense than the liquid phase! Seven out of eight materials are elements, or single atom type substances: Ga, Bi, Ge, Si, Pu, Sn & Sr.   However, there exists one compound, which I have been able to find, that also fits this description: H2O. When water freezes, its volume expands by about 9% creating an airy, open lattice structure resulting from hydrogen bonding interactions between the oxygen of one molecule to the hydrogen atom of an adjacent one. This 9% expansion is higher than most of the eight other materials that have this same property. Other substances that have strong hydrogen bonding interactions, such as ammonia, acetic acetic, or hydrofluoric acid, do not exhibit this behavior.   Other substances that are very polar like water also do not exhibit this behavior such as dimethylsulfoxide or formamide. There appears to be no other molecule that has this property. I have had students searching for a few years to find another COMPOUND that has the solid phase less dense than the liquid phase.   Even with the motivation of extra credit, the search continues for another compound that behaves like water. Even if a few others are found, this property is very, very rare.

It is amazing how normal this property is for us. Ice cubes float to the top of drinks; ponds and lakes form ice on the surface, and icebergs sail on the ocean surface. However, this is NOT the normal chemical behavior for most substances. Our everyday chemical experience is with the exceptional rather than the normal. It is hard for us to think of a floating ice cube as something unique, but it truly is.

Another amazing property of water is that liquid water’s density increases as it cools and reaches a maximum density at 4 oC. This gives the additional fortuitous property of cold water sinking as it gets colder, but to a point, then it becomes less dense and rises up. This temperature-density difference is responsible for creating the mixing effect that stirs the great bodies of water. Cold water falls to the bottom and helps push warm water to the top. This means that the whole body of water will need to cool down before ice forms in substantial amounts. This phenomena is a common experience for those of us living near the Great Lakes as we all wait to see when ice forms and if the whole lake will be ice covered.

Floating ice helps protect aquatic creatures in the winter time. This is because ice also behaves as a decent thermal insulator which further thermally protects liquid water once an ice layer forms. If you are not convinced about ice’s capacity to hold heat (i.e. high heat capacity = good thermal insulator), please read about Frederic Tudor who was an American businessman and merchant who shipped ice all over the world. Ice can serve to protect life from thermal variations, but can also be a problem. Ice cover that lasts too long and is too extensive can lead to low dissolved oxygen levels resulting in huge numbers of fish dying, commonly referred to as “winterkills”. It would seem like water should get less and less dense as it cools, but the reality is just the opposite. If any of these properties were different, ice formation would be more prolific, and it would seal oxygen away and decrease light for plants to make oxygen in the water. Another nice thing about ice floating is that ice at the surface means it is warmed up first and melted as the temperature increases. This helps the solid phase to disappear quickly as opposed to accumulating on the bottom.

Liquid water on the surface of a planet is a rare feat but having ice float on water is an even rarer chemical experience. The density of water and ice provide a unique relationship, between the solid and liquid phases of the same material, and this just so happen to be very supportive of life on planet Earth. Next time you see ice cubes floating in water, please pause and consider how unusual this experience is really supposed to be.



By Ryan T. Hayes, Ph.D.,

Associate Professor at Andrews University


Dean, J. A., Ed. (1999). Lange’s Handbook of Chemistry, McGraw-Hill.

Kramer, M. (2015). “Jupiter’s Moon Ganymede Has a Salty Ocean with More Water than Earth “. Retrieved June 14, 2016, from

Lide, D. R., Ed. (2003). CRC Handbook of Chemistry and Physics. Boca Raton, Florida, CRC Press.

Wenz, J. (2015). “23 Places We’ve Found Water in Our Solar System.” Retrieved June 14, 2016, from



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Fossils of the Galápagos: A review with implications for creationist models

Volcanic outcrops in the Galápagos Archipelago do not appear to provide the wealth of specimens found in other fossil-rich localities around the world. However, fossils are indeed present in the Galápagos Islands. This brief review addresses the where, what, when, and why of fossils in the Galápagos Islands and closes with a discussion of their potential contribution to the development of models on origins.

Where are fossils found in the Galápagos Islands?

1) Sediments that were deposited in shallow waters around the islands and were subsequently uplifted above sea level often contain fossils of marine organisms (such as mollusk shells) [1].

2) Lava tubes. Lava tubes form during volcanic eruptions, when the top of a lava flow cools and solidifies but hot melt continues to flow underneath. When lava drains from these tube-like conduits, an empty space is left underground. These tunnels and fissures often contain sediment with fossil remains of terrestrial vertebrates [2].

3) The interior of some of the islands is characterized by a more consistently humid climate. Here, small lakes and bogs, formed within inactive volcanic craters, can be found. The sediments filling the bottom of these small depressions contain fossil plant material [3, 4].

What kind of fossils are found in the Galápagos Islands?—The fossils found in the emerged shallow marine deposits are dominated by marine invertebrates such as bivalves, gastropods, bryozoans, corals, and barnacles [1, 5-7]. Not visible with the naked eye but very abundant in the sediments are also microfossils of other planktonic and bottom dwelling, small (< 2 mm), shelly animals, such as foraminifers and ostracods [5]. Rare, but sometimes found in these sediments, are skeletal fragments of marine and terrestrial vertebrates such as birds, lizards, and sea lions [1, 5, 7] (Fig. 1).

fig 1

Fig. 1: The carcass of a sea lion llies partly decomposed on a beach, Seymour North Island, Galápagos. Scale in cm. Skeletal elements from carcasses can be incorporated in beach deposits and eventually become fossilized.

Fossils collected from the lava tubes include tens of thousands of bones and bone fragments of birds, reptiles, and mammals, as well as shells of land snails [2, 8, 9]. The vertebrate remains include specimens of the most iconic Galápagos species, such as the giant tortoise, land iguana, finches, and mockingbirds, together with species of rodents, snakes, lizards, geckos, bats, and birds. Interestingly, most of these bones represent remains of preys regurgitated by Galápagos Barn Owls, a species that roost and nest on ledges in the lava tubes. Bones from larger organisms (such as giant tortoises), on the other hand, represent animals that fell and died trapped in the tubes (Fig. 2).

Fossil plant material recovered from bog and lake sediments mostly consists of microscopic pollen and spores [3, 4]. However, small-size macroscopic remains (such as seeds and plant fragments) have also been found [10].

lava tube composite

Fig. 2: A) Openings connecting to underground lava tubes, Isabela Island, Galápagos. Opening foreground has a diameter of ~50 cm. B): Carcass of a cat found inside the lava tube connected to the opening illustrated in A). Trapping and death in lava tubes in one of the processes that result in fossilization of terrestrial vertebrates in the Galápagos Islands.

When did the fossils of the Galápagos Islands form?—The question of age is a sensitive issue for creationists. There are two approaches to dating a geological object, such as a fossil or a rock. The first, called absolute dating, aims at assigning a numerical age to the object. The second, called relative dating, tries to establish if the object is younger or older than other objects but without assigning a specific numerical age.

Absolute ages in geology are based on radiometric dating methods. Radiometric ages have values that suggest a very long chronology for life on Earth, creating a potential conflict with the Scriptural record [11]. For this reason, creationists tend to reject these absolute values, looking for alternative ways of explaining these results. In general, however, there is an acceptance that the relative order of the dates (younger vs older) can be a reliable indicator of relative age, irrespective of the absolute values. In the Galápagos Islands, radiocarbon ages obtained from some of the fossil bones are almost invariably younger than 8 ka [12], with just a couple of exceptions giving values of around 20 ka [2, 8]. Radiocarbon ages of organic matter associated with the fossil plant material are also consistently younger than 26 ka [4, 13], with the exception of one layer dated as older than 48 ka [3]. Fossils in marine deposits are considered younger than 2 Ma [14], based on radiometric ages of volcanic rocks interbedded with the deposits [1]. In the standard, long-age chronology these dates correlate with the very top intervals of the geologic column (Pleistocene and Holocene). In summary, a mixed approach of absolute and relative dating seems to suggest that Galápagos fossils formed during the most recent part of Earth history, being restricted to the top layers of the geologic column.

Why are paleontologists interested in studying fossils of the Galápagos Islands?—Fossils of the Galápagos are explored as an archive of past life and ecology in the islands. Topics being pursued by paleontologists include: a) documenting patterns in species diversity and morphological trends, with potential insight on the origination of the endemic fauna and flora [2, 15]; b) studying the impact on the ecosystem of the introduction of non-native flora and fauna, with implications for ecology and conservation [2, 10]; and c) reconstructing past climatic trends and events in the island and in the tropical Pacific ocean system [3, 4].

Implications for creationist models—Although not as iconic and well known as their living counterparts, fossils of the Galápagos Islands can indeed offer some valuable contributions to the discussion of origins when approached from a creationist perspective. The following points summarize some of the most significant considerations.

Correlation with Biblical Chronology: One of the key question asked from a creationist perspective would be if the Galápagos fossils formed before, during, or after the biblical flood. Two important elements inform a possible answer that probably most creationists would embrace. First, the fossils appear to be relatively young, being found in deposits that are often within recent features of the landscape (e.g., lava tubes, craters) and associated with Pleistocene and Holocene radiometric ages. Secondly, the fossil assemblages consist almost completely of modern species, and not of extinct types [8, 15]. Most creationists would agree that modern species differ from pre-flood species, as they adapted to new environmental conditions after the flood. Therefore, when considering these two aspects, a reasonable conclusion in a creationist model would be that these fossils formed during the post-flood era.

Stasis and Rates of Evolution: From the time of Darwin, modern species in the Galápagos have been presented as a paradigmatic illustration of speciation and origin of new species from a common ancestral form. However, currently known fossils in the Galápagos do not significantly corroborate this narrative. The overwhelming majority of recovered fossils belong to known modern species, with very few examples of extinct forms [2, 6, 15, 16]. Therefore, rather than documenting gradual change, the Galápagos fossils illustrate stasis. It could be objected that transitional fossil series are not observed because the fossil record of the islands is fragmentary and represents only the most recent time interval. However, this is a suggestion based on data we do not have. What is observable does not capture evolutionary transitions.

Order in the fossil record: Different types of fossils are not distributed randomly in the geologic column but follow a specific pattern of appearance and disappearance. Fossils of the Galápagos can be used as a model to explore why various types of fossils are not all mixed up in the strata but have a certain order. Two main factors seem to be at play: time and space. There are no fossils of dinosaurs or African lions in the Galápagos. We know that African lions are not extinct, but they live only in the African continent. Therefore, the reason why lions did not fossilize in the Galápagos is linked to their geographic distribution (space). On the other hand, dinosaurs are extinct. Therefore, it could be that they never fossilized in the Galápagos because they were not present on Earth at the time of formation of Galápagos fossils (time). The presence or absence of certain groups of organisms in time and space determined the ordered distribution of fossils, both in creationist and evolutionary interpretations of the fossil record.

The Process of Fossilization: Fossils of the Galápagos can be used to show how the process of fossilization depends on both the characteristics of an organism and its depositional environment. For example, the marine creatures best represented in the Galápagos fossils are those with shells and hard parts. Soft-bodied animals, like sea cucumbers, have much lower probability of being fossilized. The environment of deposition is also crucial for fossilization. For example, volcanic lavas are not favorable for the preservation of dead organisms, but if traps where sediment can accumulate are present (e.g., the lava tubes) fossils can be found even in volcanic terrain. Furthermore, terrestrial environments (e.g., lakes and bogs) are more likely to preserve fossils of terrestrial organisms (e.g., land plants) and marine environments will tend to be dominated by fossils of marine organisms. Using the Galápagos Islands as a case study, one could conclude that fossilization is certainly not ubiquitous and does not preserve all types of organisms but even in unfavorable environments (e.g., volcanic provinces), fossilization is not as unlikely as one would think. Depicting the fossil record as highly fragmentary and incomplete might be a mischaracterization of a very rich archive of past life forms.



  1. Hickman, C.S. and J.H. Lipps, Geologic youth of Galápagos Islands confirmed by marine stratigraphy and paleontology. Science, 1985. 227(4694): p. 1578-1580.
  2. Steadman, D.W., et al., Chronology of Holocene vertebrate extinction in the Galápagos Islands. Quaternary Research, 1991. 36(1): p. 126-133.
  3. Colinvaux, P.A., Climate and the Galapagos Islands. Nature, 1972. 240(5375): p. 17-20.
  4. Collins, A.F., M.B. Bush, and J.P. Sachs, Microrefugia and species persistence in the Galápagos highlands: a 26,000-year paleoecological perspective. Frontiers in Genetics, 2013. 4: p. 269.
  5. Finger, K.L., et al. Pleistocene Marine Paleoenvironments on the Galapagos Islands. in GSA Abstracts with Programs. 2007.
  6. Ragaini, L., et al., Paleoecology and paleobiogeography of fossil mollusks from Isla Isabela (Galápagos, Ecuador). Journal of South American Earth Sciences, 2002. 15(3): p. 381-389.
  7. Johnson, M.E., P.M. Karabinos, and V. Mendia, Quaternary Intertidal Deposits Intercalated with Volcanic Rocks on Isla Sombrero Chino in the Galápagos Islands (Ecuador). Journal of Coastal Research, 2010: p. 762-768.
  8. Steadman, D.W., Holocene vertebrate fossils from Isla Floreana, Galápagos. Smithsonian Contirbutions to Zoology, 413: 104 pp.
  9. Chambers, S.M. and D.W. Steadman, Holocene terrestrial gastropod faunas from Isla Santa Cruz and Isla Floreana, Galapagos: evidence for late Holocene declines. Transactions of the San Diego Society of Natural History, 1986. 21(6): p. 89-110.
  10. Coffey, E.E.D., C.A. Froyd, and K.J. Willis, When is an invasive not an invasive? Macrofossil evidence of doubtful native plant species in the Galápagos Islands. Ecology, 2011. 92(4): p. 805-812.
  11. A discussion of creationist approaches to radiometric dating is beyond the scope of this paper, but a useful summary can be found at
  12. ka = thousands of years before present
  13. van Leeuwen, J.F., et al., Fossil pollen as a guide to conservation in the Galápagos. Science, 2008. 322(5905): p. 1206-1206.
  14. Ma = Millions of years before present
  15. James, M.J., A new look at evolution in the Galapagos: evidence from the late Cenozoic marine molluscan fauna. Biological Journal of the Linnean Society, 1984. 21(1‐2): p. 77-95.
  16. Steadman, D.W. and C.E. Ray, The Relationships of Megaoryzomys curioi, an Extinct Cricetine Rodent (Muroidea: Muridae) from the Galapagos Islands, Ecuador. Smithsonian Contributions to Paleobiology, 51: 24 pp.
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The Cenozoic

The Cenozoic is the uppermost of the three major divisions of the Phanerozoic, the other two being the Mesozoic and Paleozoic (Fig. 1). The term Cenozoic (or Cainozoic) means “recent life”, implying that the fossils encountered in these layers are more similar to modern species. Geologists divide the Cenozoic into three major systems, being, from bottom to top: the Paleogene, the Neogene, and the Quaternary. The Paleogene, is further subdivided into Paleocene, Eocene, and Oligocene, the Neogene into Miocene and Pliocene, and the Quaternary into Pleistocene and Holocene.

geol column

Figure 1: The mayor subdivisions of the geologic column.

Lower Paleocene layers are characterized by low diversity of terrestrial fauna and flora and of marine organisms, but diversity increases upwards through the layers. Plant fossils look very similar to modern species of tropical, sub-tropical and deciduous plants, including cacti and palm trees. Most fossils of mammals are only known from teeth and partial skeletons of small insectivores, herbivores, and carnivores. Most notable are the marsupial mammals, which make up more than 50% of the mammal species in the Paleocene layers of the southern continents.

Eocene fossils are recognizable as having body plans similar to living species. Geologic data suggest that there were no ice caps covering Earth’s poles and that latitudinal differences in temperature were small. Warm climate predominated in many regions of the planet facilitating the growth of large forests on Earth from pole to pole, recorded now as extensive fossil deposits of tropical to subtropical plants even in Arctic regions (Fig. 2). Tropical rainforests grew even in northern latitudes of North America and Europe. Toward the end of the Eocene, the evergreen forests were replaced by grasslands, plains and deciduous trees in North America, Eurasia and the Arctic. Similar changes happened in Antarctica, which became covered with tundra.

Minolta DSC

Figure 2: A perfectly fossilized palm frond associated with fish, from the Eocene Green River Formation, North America. This type of flora is indicative of a more subtropical climate than at present.

The first fossil representative of most of the modern mammal orders appear in the lower layers of the Eocene. A remarkable feature about these fossil mammals is their very small size compared to similar faunas of contiguous Paleocene and Oligocene deposits. Some reptiles, however, were very large, including Titanoboa, a large snake found in South America, and other reptilian megafauna. Birds are also abundant in Eocene layers, as well as fossil insects preserved in amber. Eocene layers also preserve many vertebrate fossils that lived in the oceans, including large carcharinid sharks, Basilosaurus (a large marine mammal), and sirenians.

The Oligocene sedimentary layers preserve a record of decline in temperatures, expansion of ice sheets, and global sea level fall. Important mountain building activity took place during the Oligocene, including areas such as the European Alps and western United States. In general the fossil fauna of the Oligocene, both on land and in the ocean, resembles that of modern organisms, except in South America, where large-sized litopterns, notoungulates and toxodonts (extinct orders of hoofed mammals), and extinct marsupial types lived. Some of these groups are found fossilized even in overlying strata, up to the Pleistocene (Fig. 3).

Miocene deposits record further cooling of the Earth and the extension of ice caps on both hemispheres. The Alps in Europe, the Andes in South America, and the Himalayas in Asia continued to rise, forming some of the greatest mountain ranges in the planet. Extensive grasslands allowed grazers such as horses, rhinoceroses, hippos, ground sloths, and also browsers such as camels, to thrive. All or almost all of the modern bird groups, including marine birds, are present as fossils in Miocene rocks. Marine fossils are abundant, including many specimens of marine mammals and other vertebrates. The abundance of biogenic sediments in Eocene strata indicate that the oceans sustained highly productive communities of microscopic algae (diatoms and other phytoplankton), which formed thick accumulations of diatomaceous sediments containing rich and exceptionally preserved fossils of marine mammals, birds, and reptiles.

Fig 3

Figure 3: A Pleistocene fossil toxodont from Argentina.

Pliocene layers record frequent and significant sea level changes, linked to contraction and expansion of ice sheets. Fossil Pliocene vegetation indicates a reduction of tropical species worldwide. Much of the northern hemisphere was covered by deciduous forests, coniferous forests and tundra, with grasslands spreading on all continents but Antarctica. A significant feature about the Pliocene fauna is gigantism: many species of land habitats were of large size, including mastodons, rodents, ground sloths, armadillos, glyptodonts, etc.

The Pleistocene record is dominated by the effects of glaciations that shaped the landscape in ways still discernible in North America, Russia, and the Nordic countries, as well as in mountain ranges in Asia and Europe. At the last glacial maximum, sea level decreased considerably.

During the Holocene, the global temperature rose and much of the ice that covered the northern hemisphere melted causing rapid sea level rise.

Two trends of interest emerge from this simple review of the Cenozoic fossil record. The first is that the fossil fauna and flora do not differ markedly from what observed today in terms of structure and major higher taxonomic groups. In other words, the type of life documented in Cenozoic layers does not appear to be fundamentally different from what seen in the modern world. The second is the importance played by climate patterns in shaping the geologic record of the Cenozoic, with a major trend for climate deterioration and establishment of glaciation, only recently reversed. Both these macro-scale observations could fit well with a model of the Cenozoic as representing geologic, climatic, and biologic processes unfolding in the post-flood world.


By Raul Esperante, PhD

Geoscience Research Institute

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The Mesozoic

Few things in science evoke more interest in children than dinosaurs. Books, films, toys, etc. continue to fuel kids’ interest in the very alien world of our past, yet few Christians know how to respond to their children’s curiosity in a way that is both biblically sound and scientifically accurate. Although a full discussion of the fossils in Mesozoic rocks would require several volumes, a brief synopsis is presented here along with some creationist reflections for those who are interested – parents or otherwise.

066 fix

Skeleton of Tyrannosaurus rex from the Black Hills Institute of South Dakota.

The Mesozoic (“middle life”) Erathem is composed of three systems: the Triassic, Jurassic, and Cretaceous. These Mesozoic rocks make up the middle of the Phanerozoic – the rocks containing most of the fossils we find – sandwiched between the Paleozoic (“old life”) and Cenozoic (“new life”) erathems. As is the case with the rest of the geologic column, the higher one journeys in the column, the younger the rocks are, and the more the fossils within them resemble the life in our present world.

The lowest, and therefore oldest, rocks of the Mesozoic are called the Triassic. The Triassic picks up right after the Permian, the last of the Paleozoic systems. Animal fossils change drastically across the boundary between the Permian and the Triassic, such that evolutionists refer to this as the Permo-Triassic Extinction, thought to be the largest extinction event in earth’s history. Despite the great faunal extinctions, plants go through the P/T Extinction relatively unscathed. This is an interesting phenomenon of the fossil record: plant extinctions and animal extinctions do not seem to line up as would be expected from an evolutionary perspective. Dramatic changes in the flora can be found in the middle Permian and later within the Cretaceous system. The dominant type of plants found in the Mesozoic, up until the Lower Cretaceous, are gymnosperms – plants such as conifers, gingkoes, cycads, and cycadeoids (an extinct group). In the Lower Cretaceous, however, there is an explosive radiation of a completely different type of plant: angiosperms, the flowering plants. Angiosperms dominate our ecosystems today, but they are totally absent from rocks below the Lower Cretaceous – except for some possible Triassic pollen (Hochuli and Feist-Burkhardt, 2013) and a possible Jurassic flower (Liu and Wang, 2015).

What are we to make of the absence of flowering plants – the overwhelmingly dominant form of plant today – in the Triassic and Jurassic? There is almost nowhere you can go on our earth today where you will not find angiosperm pollen. How could the past have been so different? The evolutionist suggests that angiosperms evolved during the Mesozoic from some kind of gymnosperm ancestor, but such transitional fossils are lacking, leaving the event shrouded in mystery. Perhaps, as will be discussed later, the answer lies in segregated ecosystems.

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Skull of a stereospondyl amphibian from the Los Angeles County Museum of Natural History.

The vertebrate animals found in Lower and Middle Triassic rocks would have seemed very foreign to us were we to meet them today, although many of our familiar invertebrates are found in these rocks. There are no crocodiles before the Upper Triassic. Instead, there are crocodile-mimics called phytosaurs and stereospondyl amphibians. There are no large, herbivorous mammals to be found here like cows, sheep, antelope, or deer; rather, we see vast numbers of dicynodonts – tusked and beaked “mammal-like reptiles” – as well as sharply-beaked reptiles called rhynchosaurs. There are no dolphins, seals, or sea turtles – there are dolphin-shaped ichthyosaurs, long-necked nothosaurs, and often turtle-mimicking, clam-crushing placodonts. Instead of armadillos, there are large-reptilian tanks with upturned noses: aetosaurs. There are no birds, frogs, salamanders, or snakes to be found in these rocks.

Then, in the Upper Triassic rocks, there is a sudden change. Several groups make their presence known for the first time in these strata: crocodilians, turtles, dinosaurs, pterosaurs (“pterodactyls”), and even mammals (Bi, et al., 2014). In the Triassic, dinosaurs and dinosaur-like animals are already surprisingly diverse with small and large carnivores and herbivores of various shapes. The pterosaurs, too, are fully-formed and diverse when first found in the record. This is not what we should expect given Darwinian evolution, where a new group should evolve and increase in diversity over time. Instead, we see rapid appearances of new groups in the fossil record, already very diverse.

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Skull of the mosasar Platecarpus from the Los Angeles County Museum of Natural History.


With the start of the Jurassic rocks, most of the bizarre Triassic groups mentioned in the last paragraph have disappeared, except ichthyosaurs and stereospondyls, and even more groups have appeared including lizards and modern amphibians. Dinosaurs are even more diverse in the Jurassic, and some forms get enormous. Notably, the sauropods – dinosaurs like Brachiosaurus, Apatosaurus, and Brontosaurus (now a valid genus again (Tschopp, et al., 2015)) – were the largest land animals to have ever lived, some of which reached lengths over 30 meters! Other new dinosaurs can be found in the Jurassic including armored dinosaurs like Stegosaurus and large carnivores like Allosaurus and Ceratosaurus.

Plesiosaur swimming Paddle

Image: Plesiosaur flipper showing hyperphalangy (the condition of increasing number of phalanges (finger bones) for already existing digits from the South Dakota School of Mines.

Marine rocks suggest oceans teeming with long-necked, four-flipped plesiosaurs and ammonoids with straight and coiled shells. Many new pterosaur types appear in the Upper Jurassic and Lower Cretaceous strata including the filter-feeding ctenochasmatids and the shell-crushing dsungaripterids (Witton, 2013). Notably, the first bird (although maybe not (Xu, et al., 2011; Agnolín and Novas, 2013)) in the fossil record, Archaeopteryx, is found in Middle Jurassic rocks. Although possessing the feathers expected for a bird, it also has several dinosaurian traits including a long bony tail, teeth in its jaws, and clawed hands, evidences which have been used to argue for its transitional state between theropod dinosaurs and birds. Interestingly, many of the most bird-like dinosaurs are found in Cretaceous rocks, and Archaeopteryx and its allies, Anchiornis, Xiaotingia, and Aurornis, seem to show up suddenly in the fossil record with no immediate ancestors.


Apart from the appearance of flowers, and their pollinators: bees, in the Cretaceous, this system of rocks is notable for its dinosaur diversity. Large, occasionally-bipedal herbivores like Iguanodon and the duck-billed hadrosaurs dominate Cretaceous ecosystems along with the quadrupedal horned dinosaurs including Triceratops and Centrosaurus. Rarer in the fossil record are the heavily armored ankylosaurs and the bipedal, dome-headed pachycephalosaurs. New theropod groups, including the herbivorous ground sloth-mimicking therizinosaurs, the toothless ostrich-mimics (ornithomimosaurs) and oviraptorosaurs, and the alvarezsaurs, which possessed only one finger on each hand, appear for the first time in the Cretaceous. Small, carnivorous theropods included the famous dromaeosaurs, such as Deinonychus and Velociraptor. The biggest carnivorous theropods are found in the Cretaceous: the tyrannosaurs and the southern hemisphere’s caracharodontosaurids (although Veterupristisaurus is Jurassic (Rauhut, 2011)). Pterosaurs also reached gargantuan sizes, with azhdarchids like Quetzalcoatlus reaching 10-11 meters in wingspan! Despite these enormous animals, the largest Cretaceous mammal is only the size of a Virginia opossum (Hu, et al., 2005). Birds of various kinds, including enantiornithines, are found in many Cretaceous deposits, and mosasaurs – giant, four-flippered sea serpents – dominate the oceans. The first snakes, interestingly possessing four limbs, are also found in Cretaceous rocks (Martill, et al., 2015).

Triceratops skull

Triceratops skull from the Los Angeles Museum of Natural History

Then, with the transition from the Cretaceous to the Paleogene, it all changes. There are no ammonoid, ichthyosaur, plesiosaur, mosasaur, pterosaur, or dinosaur fossils higher than the Cretaceous. Mammals, birds, crocodiles, frogs, lizards, snakes, insects, and other animals continue to be found in Cenozoic rocks, but the absence of the others is a mystery. The most popular explanation in evolutionary circles is that a large asteroid hit the earth, killing the dinosaurs. Smaller animals, such as mammals and birds, were able to survive, whereas the large dinosaurs could not. However, this scenario is obviously too simplistic. Why would the asteroid kill ammonoids, and leave squids? Why did small dinosaurs die when birds did not?


Perhaps a better explanation is that the K-Pg boundary represents the end of Noah’s Flood. The Cenozoic, then, represents the recolonization of the earth. Certain animals: dinosaurs, pterosaurs, etc. were unable to survive in the post-Flood world, whereas others were incredibly successful. Perhaps this explains why the Triassic and other systems possess equivalents to today’s animals, rather than our modern forms. Crocodilians and phytosaurs lived in different pre-Flood ecosystems, but after the Flood, the extinction of phytosaurs allowed crocodilians to take over all kinds of compatible ecosystems. Frogs are never found in the Carboniferous or Permian, despite being a place Kermit would love to call home, because there are other animals already in the environments preserved in those systems: microsaurs, dissorophoids, and branchiosaurs. Frogs could have been restricted to certain areas before the Flood, but in the post-Flood world they would have been able to spread themselves all over the world while many other amphibian groups could not and went extinct. Instead of always taking our current world and trying to fit the past into it, maybe we need to recognize that the place outside our windows is the recovery from a worldwide catastrophe, and as such is actually not the norm for earth’s history.


M. Aaron

Geoscience Research Institute



Agnolín, F.L. and Novas, F.E. 2013. Avian ancestors. A review of the phylogenetic relationships of the theropods Unenlagiidae, Microraptoria, Anchiornis, and Scansoriopterygidae. SpringerBriefs in Earth System Sciences: 1-96.

Bi, S., Wang, Y., Guan, J., Sheng, X., and Meng, J. 2014. Three new Jurassic euharamiyidan species reinforce early divergence of mammals. Nature 514: 579-584.

Hochuli, P.A. and Feist-Burkhardt, S. 2013. Angiosperm-like pollen and Afropollis from the Middle-Triassic (Anisian) of the Gemanic Basin (Northern Switzerland). Frontiers in Plant Science 4: 344.

Hu, Y., Meng, J., Wang, Y., and Li, C. 2005. Large Mesozoic mammals fed on young dinosaurs. Nature 433: 149-152.

Liu, Z.-J. and Wang, X. 2015. A perfect flower from the Jurassic of China. Historical Biology. DOI: 10.1080/08912963.2015.1020423.

Martill, D.M., Tischlinger, H., and Longrich, N.R. 2015. A four-legged snake from the Early Cretaceous of Gondwana. Science 349(6246): 416-419.

Rauhut, O.W.M. 2011. Theropod dinosaurs from the Late Jurassic of Tendaguru (Tanzania). Special Papers in Palaeontology 86: 195-239.

Tschopp, E., Mateus, O.V., and Benson, R.B.J. 2015. A specimen-level phylogenetic analysis and taxonomic revision of Diplodocidae (Dinosauria, Sauropoda). PeerJ 3: e857.

Witton, M.P. 2013. Pterosaurs. Princeton University Press, Princeton, New Jersey.

Xu, X., You, H., Du, K., and Han, F. 2011. An Archaeopterx-like theropod from China and the origin of Avialae. Nature 475(7357): 465-470.

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The Paleozoic Rock Record: A Broad Overview of Features and Trends

The rocks of the Earth are like pages of a history book containing information about the past. Geologists who enjoy reading this “book” have found that it consists of two “volumes:” the first, named Precambrian, is mostly devoid of macroscopic fossils. The second, named Phanerozoic, contains layers and sediments providing a rich archive of past forms of animal and vegetal life. The Phanerozoic “volume” is further subdivided in three “sections,” called Paleozoic, Mesozoic and Cenozoic, each consisting of several “chapters” (Fig. 1) [1].

geol column

Fig. 1: The geologic column, with its standard subdivisions, including the Paleozoic and its systems.

This article focuses on the Paleozoic interval of the geologic record. Estimates from global compilations of maps suggest that about 20% of the surface of the Earth is covered by Paleozoic rocks [2]. These rocks are usually well preserved, although mineralogical modifications (e.g., recrystallization) and physical disruption (e.g., faulting and folding) are common. Therefore, Paleozoic rocks represent a substantial and accessible part of the rock record and attempting a comprehensive synthesis of their main characteristics in a blog post is an impossible task. This overview concentrates on selected topics about Paleozoic sedimentary rocks, igneous rocks, fossil patterns, and tectonics. The article will close with some suggestions on the significance form a creationist perspective of salient features and trends in Paleozoic rocks.


Paleozoic Sedimentary Rocks

1) Global Stratigraphic Signal. There is a great variety of types represented in Paleozoic sedimentary rocks. However, when looking at the macroscale, certain types of rocks show a specific frequency increase within the Paleozoic or some of its intervals. This non-random pattern of stratigraphic distribution [3] is often observed on a global scale. Examples include: Cambrian sandstone composed almost exclusively of quartz (Fig. 2), found across most of the North American continent and documented on other continents [4]; peaks in abundance of carbonate deposits in the lower and mid-Paleozoic [4, 5], including (for the lower Paleozoic) globally distributed facies such as stromatolites [6] and flat-pebble conglomerates (Fig. 3) [7]; widespread marine black shales, rich in organic carbon, common in the lower Paleozoic and upper Devonian-Mississippian [8]; abundant reef-like deposits in the Silurian and especially in the Devonian [9, 10]; immense coal deposits in the Pennsylvanian and Permian [11]; and extremely wide and thick accumulations of evaporites in the Permian [12].

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Fig. 2: An example of Cambrian quartzite, consisting of well rounded and well sorted quartz granules. Sawatch Quartzite, Manitou Springs area, Colorado, USA. Penny for scale is 2 cm wide.

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Fig. 3: An example of Cambrian flat pebble conglomerate, consisting of variously orientated elongated limestone pebbles, several cm in size. Notch Peak Formation, Millard County, Utah, USA. Scale increments are 1cm wide.

2) Widespread Marine Deposition over the Continents. Lower to mid-Paleozoic sedimentary rocks are remarkable in documenting large-scale flooding and establishment of seas over continental interiors. This is perhaps best seen in the North American rock record, where up to four major successive continent-wide flooding phases can be observed in Paleozoic deposits [13]. The topography of the submerged continents must have been very subdued because the layers deposited over the flooded landscape generally show extremely high lateral continuity and flat basal contacts (Fig. 4). In some cases, even thin beds only a few cm thick can be followed laterally for tens of kilometers [14].


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Fig. 4: A classic example of flat contacts between laterally widespread Paleozoic layers. Grand Canyon, Arizona, USA.

3) Upward Increase in Terrestrial Deposits. If it is true that the lower to mid-Paleozoic is dominated by marine deposits even over continental landmasses, terrestrial deposits become substantially more represented in the upper Paleozoic, from the Pennsylvanian upward [15]. In addition, the style of fluvial deposition also appears to differ, with predominantly sheet-like sandy deposits in the lower Paleozoic being complemented from the mid-Paleozoic upward by mud-rich deposits, interpreted as more typical of meandering rivers [16].


4) From Low to High Frequency Cyclicity

When tracing rock units along the vertical direction, it is common to see repetitions of certain types of deposits (e.g., sandstone, mudstone, limestone). The cyclical pattern in these rock types reflects changes in the environments of deposition, such as variations in water depth and sediment supply. These changes in rock types, often marked by discontinuity surfaces between packages of layers, are observed throughout Paleozoic sedimentary deposits. However, in the upper Paleozoic (starting from the upper Mississippian) a marked increase in the frequency of these sedimentary cycles is observed on a global scale [17]. Broadly speaking, lower to mid-Paleozoic relatively monotonous deposits are overlain by cyclical successions more intensely punctuated by discontinuities and alternations of different rock types.


Paleozoic Igneous Rocks

1) Volcanic Rocks. It is difficult to systematically address global trends in volumes and types of volcanism during the Paleozoic, because of limitations due to the incomplete nature of the rock record. Notably, while basaltic rocks of the ocean floor offer a continuous record of submarine volcanism for the Cenozoic and part of the Mesozoic, only slivers of Paleozoic oceanic crust are preserved. However, Paleozoic rocks do contain a record of some notable episodes of volcanic activity. For example, Upper Ordovician deposits from North America and Europe contain a cluster of ash layers attributed to some of the largest explosive volcanic eruptions ever recorded in the whole Phanerozoic [18, 19]. Large igneous provinces (LIPs), which are regions preserving immense volumes of lava effused within a very narrow stratigraphic interval, have also been documented for the Paleozoic. They include Cambrian, Devonian, and Permian examples, the most spectacular being the Siberian Traps in Russia, where an estimated volume of over 2 million km3 of magma were mobilized at the very end of the Paleozoic [20].


2) Plutonic Rocks. Plutonic rocks form from the solidification of magma at depth in the Earth’s crust and constitute the core of the continents. The study of plutonic rocks, therefore, helps to understand the timing and process of formation of the continents. For example, it would be interesting to know how much of the continental crust formed or was recycled during the Paleozoic. Limitations in dating and the incompleteness of the rock record hamper these types of reconstructions. However, some clues can be obtained in indirect ways. Zircon, for example, is a mineral that forms during the crystallization of magma and is very durable and resistant. Even if the original intrusive rock hosting a zircon is eroded, the detrital zircon may survive and be included in younger rocks. Studies looking at the age distribution of detrital zircons indicate that the Paleozoic was one of several intervals with significant crystallization or recycling of crust [21]. Another way to assess the Paleozoic production of plutonic rocks is to look at their preserved surface area compiled from geologic maps. It appears that Paleozoic plutonic rocks are more abundant on the Earth’s surface than their Precambrian or Cenozoic counterparts [22]. This confirms that the Paleozoic was an interval of significant magma emplacement and crystallization.


Paleozoic Fossil Patterns

1) Diversity Trends. The most remarkable aspect of the Paleozoic rock record is the abundance of macroscopic animal fossils when compared with underlying Precambrian rocks. This major transition has been called the “Cambrian explosion” and occurs in lower Cambrian strata, where fossils of most animal phyla first appear [23]. An equally important interval is what has been called the Great Ordovician Biodiversification Event (GOBE), referring to a remarkable increase in diversity of marine fossil groups in the Lower to Mid-Ordovician [24]. The Cambrian explosion is unique for the sudden appearance of a large number of new animal body plans, but the GOBE shows the greatest increase in diversity of fossil forms within already known body plans. As a result of these two important stratigraphic intervals, Paleozoic marine faunas can be broadly divided in two groups [25]: the Cambrian fauna (dominated by trilobites) and the overlying Paleozoic fauna (dominated by suspension feeders such as brachiopods, bryozoans, crinoids, and corals) (Fig. 5). These faunas are punctuated by several turnovers at specific stratigraphic levels (e.g., top of Ordovician and, most significantly, top of Permian), where the coordinated disappearance of certain groups is observed [26].

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Fig. 5: Close up view of a typical example of a lower Paleozoic marine fossil assemblage after the GOBE. Brachiopods, bryozoans, and crinoids make up most of the skeletal fragments seen in the picture. Upper Ordovician Richmond Group, Hueston Woods State Park, Ohio, USA. Scale increments are in cm.

2) Ecological Trends. Along with increased diversity, the GOBE seems to mark a shift to marine faunal assemblages representative of greater ecological complexity [24]. Cambrian layers contain mostly invertebrates that lived on the surface of bottom sediments, but overlying strata include planktonic organisms, fish, burrowers, and suspension feeders that stood taller above the bottom because they were erect. Another important transition is observed in mid-Paleozoic strata, where the fossil record ceases to include only marine organisms and begins to document terrestrial organisms. Macroscopic fossils of land plants first appear in the Silurian and become more common in the Devonian [27], terrestrial invertebrates (including insects, spiders, and millipedes) first appear in the Devonian [28], and a few tracks and remains of land vertebrates first appear in the Devonian [29] but become common in the Carboniferous. Notable groups completely absent from Paleozoic layers are dinosaurs, mammals, birds, and flowering plants.


Paleozoic Plate Tectonics

Reconstructions based on paleomagnetism and distribution of major orogenic belts seem to indicate that the initial Paleozoic configuration of continents consisted of four distinct major continental masses, one of which (named Gondwana) grouped all the current continents of the southern hemisphere [30]. Interestingly, whereas most of the margins of these continents show lowermost Paleozoic patterns of sedimentation typical of passive, extensional margins, a remarkable tectonic shift is observed in the Upper Cambrian to Ordovician, where most of these continental margins show evidence for the onset of large scale active convergence [31]. An intriguing aspect of Ordovician plate tectonics is that none of the widespread convergent margins seem to involve collision between continents but only accretion of microcontinents and volcanic arcs, a condition not seen in any other part of the Phanerozoic [32]. A sustained trend of convergence is consistently documented by orogenic belts along continental margins throughout the Paleozoic, resulting in the progressive amalgamation of the different continental masses. Paleogeographic reconstructions indicate that the continents were finally assembled into a supercontinent (named Pangea) by the Early Permian, a configuration that persisted to the end of the Paleozoic [33].

Another feature of interest for Paleozoic plate tectonics is the suggestion of a Cambrian episode of significant true polar wander [34, 35]. This phenomenon implies the redistribution of continental masses with respect to Earth’s axis of rotation resulting in movements of tens of degrees of latitude (e.g., from polar to tropical latitudes) and representing a mechanism of plate motions faster than and different from classic plate tectonics.


The Paleozoic: A Creationist Perspective

The existence of a discontinuity in terms of fossil content between the Precambrian and the Paleozoic makes it tempting for creationists to link this horizon to a major discontinuity in Earth’s history. This perception is reinforced when considering that the base of the Paleozoic is often expressed with a physical stratigraphic discontinuity [4] that marks a mechanical-erosional boundary and a significant shift in sedimentary and tectonic conditions [36].

From a biblically informed perspective, a possible candidate to generate such discontinuity would be the global flood of Genesis 6-8. Some Paleozoic sedimentary patterns would fit well on a general level with the description of the biblical catastrophe, in particular the patterns of extensive flooding of continental masses and global signature in the style of sedimentation. Extensive plate rearrangements could also be hypothesized as part of the flood event, and the lowermost Paleozoic presents an interesting interval where both fast plate reorganization and change in predominant tectonic regime seem to be documented. Certainly, plate tectonics offer an important background mechanism to explain several Paleozoic trends. For example, the progressive assembly of Pangea might have controlled the Paleozoic trend in increasing terrestrialization observed both in the sedimentary and fossil record. Interestingly, this parallel increase in preservation of continental deposits and land fossils supports the suggestion of creationists that trends in appearance of fossil groups result at least in part from sampling of different habitats and ecosystems rather than biological evolution. The trend toward a supercontinent configuration might also have played a role in the switch to higher frequency cyclicity observed in the upper Paleozoic sedimentary record, as clastic material from exposed landmasses with extensive drainage systems became more available. Finally, active plate convergence during the Paleozoic would account for the modal peak in Paleozoic igneous rocks, as continental collision settings tend to be favorable for the preservation of new continental crust [37].

In the modern history of creationism, the general consensus about where to place Paleozoic rocks in biblical history has followed an interesting trajectory. The majority of Scriptural geologists, in the first half of the 19th century, assigned the formation of Paleozoic rocks to the time between Day 3 of creation and the onset of the flood [38]. The trend was decidedly reversed in the 20th century, when key figures such as G. Price, H. Clark, H. Morris, and J. Whitcomb clearly interpreted the formation of Paleozoic fossil-bearing rocks as a consequence of the flood [39]. In the past two decades, there has been renewed consideration among some creationists of the possibility that part of the Paleozoic might have been deposited before the flood [40, 41].

Given the immensity of data archived in the Paleozoic rock record, any attempt at a synthetic model from a creationist perspective will have to find the delicate balance between an ability to see the bigger picture without overlooking important details. Before that balance is reached, an exciting work of study and discovery will continue to accompany us in our journey.

Ronny Nalin, PhD

Geoscience Research Institute



  1. This article adopts the standard geologic column as a reliable indicator of the spatial stratigraphic order of rocks, without endorsing the absolute chronology attached to it. For more on this approach, see our previous blog post Patterns in the fossil record at
  2. Dürr, H.H., M. Meybeck, and S.H. Dürr, Lithologic composition of the Earth’s continental surfaces derived from a new digital map emphasizing riverine material transfer. Global Biogeochemical Cycles, 2005. 19(4): p. n/a-n/a. This study estimates that Paleozoic sedimentary and volcanic rocks cover 15.8% of Earth’s surface. However, metamorphic and igneous rocks are not included in the estimate. The undifferentiated cover of metamorphic and igneous rocks is estimated at about 12% of Earth’s surface. Assuming that one third of this 12% of undifferentiated cover is Paleozoic, we arrive at the 20% figure.
  3. For a recent treatment of this feature of the stratigraphic record see Brett, C.E., et al., Time-specific aspects of facies: State of the art, examples, and possible causes. Palaeogeography, Palaeoclimatology, Palaeoecology, 2012. 367–368(0): p. 6-18.
  4. Peters, S.E. and R.R. Gaines, Formation of the `Great Unconformity’ as a trigger for the Cambrian explosion. Nature, 2012. 484(7394): p. 363-366.
  5. Mackenzie, F.T. and J.W. Morse, Sedimentary carbonates through Phanerozoic time. Geochimica et Cosmochimica Acta, 1992. 56(8): p. 3281-3295.
  6. Riding, R., Microbial carbonate abundance compared with fluctuations in metazoan diversity over geological time. Sedimentary Geology, 2006. 185(3–4): p. 229-238.
  7. Kim, J.C. and Y.I. Lee, Flat-Pebble Conglomerate: A Characteristic Lithology of Upper Cambrian and Lower Ordovician Shallow-Water Carbonate Sequences, in Ordovician Odyssey, Short papers, International Symposium on the Ordovician System, 7th, Fullerton, California Pacific Section, SEPM (Society for Sedimentary Geology). 1995. p. 371-374.
  8. Arthur, M.A. and B.B. Sageman, Marine Black Shales: Depositional Mechanisms and Environments of Ancient Deposits. Annual Review of Earth and Planetary Sciences, 1994. 22(1): p. 499-551.
  9. Kiessling, W., Geologic and Biologic Controls on the Evolution of Reefs. Annual Review of Ecology, Evolution, and Systematics, 2009. 40(1): p. 173-192.
  10. Copper, P. and C.R. Scotese, Megareefs in Middle Devonian supergreenhouse climates, in Extreme depositional environments: Mega end members in geologic time, M.A. Chan and A.W. Archer, Editors. 2003, Geological Society of America Special Paper 370 Boulder, Colorado. p. 209-230.
  11. de Sousa e Vasconcelos, L., The petrographic composition of world coals. Statistical results obtained from a literature survey with reference to coal type (maceral composition). International Journal of Coal Geology, 1999. 40(1): p. 27-58.
  12. Warren, J.K., Evaporites through time: Tectonic, climatic and eustatic controls in marine and nonmarine deposits. Earth-Science Reviews, 2010. 98(3–4): p. 217-268.
  13. Sloss, L.L., Sequences in the Cratonic Interior of North America. Geological Society of America Bulletin, 1963. 74(2): p. 93-114.
  14. Brett, C.E., P.I. McLaughlin, and G.C. Baird, Eo-Ulrichian to Neo-Ulrichian views: The renaissance of” layer-cake stratigraphy”. Stratigraphy, 2007. 4: p. 201-2015.
  15. Wall, P.D., L.C. Ivany, and B.H. Wilkinson, Revisiting Raup: exploring the influence of outcrop area on diversity in light of modern sample-standardization techniques. Paleobiology, 2009. 35(1): p. 146-167.
  16. Davies, N.S. and M.R. Gibling, Cambrian to Devonian evolution of alluvial systems: The sedimentological impact of the earliest land plants. Earth-Science Reviews, 2010. 98(3–4): p. 171-200.
  17. Wright, V.P. and S.D. Vanstone, Onset of Late Palaeozoic glacio-eustasy and the evolving climates of low latitude areas: a synthesis of current understanding. Journal of the Geological Society, 2001. 158(4): p. 579-582.
  18. Mason, B.G., D.M. Pyle, and C. Oppenheimer, The size and frequency of the largest explosive eruptions on Earth. Bulletin of Volcanology, 2004. 66(8): p. 735-748.
  19. Sell, B., L. Ainsaar, and S. Leslie, Precise timing of the Late Ordovician (Sandbian) super-eruptions and associated environmental, biological, and climatological events. Journal of the Geological Society, 2013. 170(5): p. 711-714.
  20. Ernst, R.E. and K.L. Buchan, Large mafic magmatic events through time and links to mantle-plume heads, in Geological Society of America Special Papers 352, R.E. Ernst and K.L. Buchan, Editors. 2001: Coulder, CO. p. 483-575.
  21. Voice, P.J., M. Kowalewski, and K.A. Eriksson, Quantifying the Timing and Rate of Crustal Evolution: Global Compilation of Radiometrically Dated Detrital Zircon Grains. The Journal of Geology, 2011. 119(2): p. 109-126.
  22. Wilkinson, B.H., et al., Global geologic maps are tectonic speedometers—Rates of rock cycling from area-age frequencies. Geological Society of America Bulletin, 2009. 121(5-6): p. 760-779. This surface distribution only refers to plutonic rocks that have not been subsequently metamorphosed, therefore excluding orthogneisses or other crystalline rocks derived from a plutonic precursor.
  23. Marshall, C.R., Explaining the Cambrian “explosion” of animals. Annual Review of Earth and Planetary Sciences, 2006. 34(1): p. 355-384.
  24. Servais, T., et al., Understanding the Great Ordovician Biodiversification Event (GOBE): Influences of paleogeography, paleoclimate, or paleoecology. GSA Today, 2009. 19(4): p. 4-10.
  25. Sepkoski, J.J., A Factor Analytic Description of the Phanerozoic Marine Fossil Record. Paleobiology, 1981. 7(1): p. 36-53.
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  27. Edwards, D. and N.D. Burgess, Plants, in Paleobiology: A Synthesis, B. D.E.G. and P.R. Crowther, Editors. 1990, Blackwell Scientific Publications. p. 60-64.
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  36. Snelling, A., Earth’s Catastrophic Past: Geology, Creation, & the Flood. 2009, Dallas (TX): Institute for Creation Research, pp. 707-711
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  38. For an in depth historical analysis of scriptural geologists se the series of articles by T. Mortenson available at
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41.       Gentet, R.E., The CCC Model and its geologic implications. Creation Research Society Quarterly, 2000. 37: p. 10-21.

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