August 2016 
Meagan Wall Presents at URTeC
(Image by Theopolisme on WikiMedia.)

The fourth Unconventional Resources Technology Conference was held in San Antonio this year, and StratoChem was of course present.  But we didn't just attend; our very own U.S. Project Manager & Business Geochemist Meagan Wall presented her paper, "An Oil-Source Rock Correlation Examining the Potential of the Chattanooga Shale as a Source Rock for Oil Within the Spivey-Grabs-Basil Field, Kingman and Harper Counties, Kansas."  It was an exciting and eye-opening example of the creative use of geochemistry to determine source rock potential in an unconventional play. If you attended URTeC, we hope you stopped by, but we'll be happy to share the presentation with you if you couldn't make it.

Your Friends at StratoChem Services

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The Western Interior Seaway
by Hunter C. Eden

I feel a certain awe in the presence of history: the Great Pyramid of Giza, Machu Picchu, Stonehenge, Chichen Itza. . . .These places feel like gifts from the past, unique and rare testaments to time periods I can't experience in any other way.  But Denver, the very city in which I live, has something almost as incredible: the ground beneath our feet.

A good hundred and thirty million years ago (give or take), geologists tell us that the Farallon Plate began to subduct beneath the North American Plate.  The angle was shallow, but this subduction profoundly affected the landscape above.  Facilitated by a warm climate completely lacking polar ice caps, this subduction created an inland sea that, thirty million years later, stretched from the Arctic Ocean down to the Gulf of Mexico, forming the area we today call the Western Interior Seaway (or sometimes the Niobraran Sea), a two-thousand mile expanse of open water that played host to an ecosystem unlike any the earth had ever seen.

I've often said the only bad thing about Denver is that it lacks an ocean. I only missed it by about 75 million years.

The Western Interior Seaway was never particularly deep.  Its greatest observed depth was only 2,500 feet (by comparison, Russia's Lake Baikal is more than twice that at 5,387 feet), with an average of only 600 feet.  But its shallow waters supported a thriving tropical sea with a rich variety of life, from massive beds of calcareous algae (preserved today in places like Kansas's Monument Rock) to some of the most fearsome aquatic predators of all time.

These latter fossils draw our attention most.  Mosasaurs, carnivorous reptiles attaining nearly fifty feet in length, dominated the food chain, enthroned as top predators in a world where competition for the title was fierce.  Mosasaurs co-existed with dinosaurs but were only distantly related, their closest living relatives being monitor lizards (the genus including the famous Komodo dragon).  

Tylosaurus proriger , top predator of the Western Interior Seaway--because prehistory needed a giant, swimming, Komodo dragon.
(Image by DiBgd on Wikipedia).

Typified by monsters like Tylosaurus proriger , the mosasaurs of the Western Interior Seaway were indiscriminate carnivores, taking prey as diverse as fish (including large sharks), other aquatic reptiles, and on occasion, each other.  At least one fossil dinosaur of an unidentifiable duck-billed species bears distinctive mosasaurid toothmarks, leading paleontologists to believe that these opportunistic predators scavenged carrion washed off the shores of the Western Interior Seaway.

Plesiosaurs like  Elasmosaurus platyurus were another typical sight in the Western Interior Seaway. Roughly as long as  Tylosaurus but with much of its body length taken up by neck,  Elasmosaurus
and its smaller cousins sometimes became prey for larger mosasaurs.  Nevertheless, it was a fearsome predator specialized in preying on fish and mollusks, including the coil-shelled cephalopods known as ammonites.

 Elasmosaurus platyurus  with unlucky diver for scale (Image by DiBgd on Wikipedia).

While the bodies of plesiosaurs lacked the hydrodynamic shape of mosasaurs or the dolphin-like icthyosaurs they ultimately succeeded, their long necks made them efficient hunters. Despite common portrayals, osteological studies show that plesiosaurs lacked the flexibility necessary to lift their heads above water in an s-shaped pose, and seem to have struck at prey from the side in a more snake-like fashion.

Below the plesiosaurs and mosasaurs, fish filled the middle tier of the Western Interior Seaway's ecosystem.  Sharks like Cretoxyrhina , a distant extinct relative of the great white, and the impressively fanged Xiphactinus , a predatory bony fish capable of attaining 6 meters in length, even preyed on smaller mosasaurs.

The rather terrifying Xiphactinus audax .

Flying reptiles and birds were also in evidence.  The most famous of these is doubtless Pteranodon , an iconic pterosaur that subsisted on a diet of fish.  Despite its size (wingspans sometimes exceeding eighteen feet), Pteranodon was a capable flyer.  While the purpose of its long head-crest is unknown, only males seem to have possessed it, perhaps indicating its use in mating rituals.   Hesperornis was a toothed diving bird somewhat similar to a loon, though this is due more to convergent evolution than any actual relation.  At about five feet long, it was well-adapted to life in the water but likely could not stand up on land due to the positioning of its feet, necessitating movement like a seal or walrus.

Pteranodon longiceps  in flight (image by Matt Martinyiuk).

But as impressive as some of these prehistoric monsters were, it may be the most humble denizens of the Western Interior Seaway that shed the greatest light on the mechanisms that allow some species to survive and force others into extinction.  As the Laramide Uplift slowly forced the Western Interior Seaway into dry land, the fossils of its denizens were preserved in the formations of the newly forming Rockies.  These included the mosasaurs and plesiosaurs, of course, but also the many mollusks that shared their environment: clams, ammonites, and belemnites.

An ammonite, named after the ram-horned Egyptian god Ammon. You knew there would be an Egyptian reference somewhere in this article (image by Nobu Tamura).

Through studies of these mollusks, scientists began to notice a pattern to the extinctions occurring in the Western Interior Seaway--and it wasn't what they expected.  As in the present, some species in the Seaway had broader ranges than others.  Corinne Myers and a team of paleontologists affiliated with the University of Kansas looked into these patterns, expecting the environmental upheavals that occurred at various points in the Seaway's history to kill off the more localized species and allow the more widespread ones to survive.  

In many cases, Myers's team found the exact opposite: the more widespread species also depended most heavily on very specific conditions in the Western Interior Seaway at the time.  When those conditions changed, whether due to climatic effects, geological upheavals, or other factors, the more numerous species died off, and the more generally-adapted local species took their niches.

It's a cogent lesson, as we move into what an increasing number of biologists call the Anthropocene, the epoch in which the greatest evolutionary pressure upon living species comes from human impacts on the environment.  The fossil record underneath the Rockies may allow us to predict which species will be best suited to the changing world around us.

Not bad for a city only founded in 1858.