Mesozoic sauropods, like many modern herbivores, are likely to have hosted microbial methanogenic symbionts for the fermentative digestion of their plant food. Today methane from livestock is a significant component of the global methane budget. Sauropod methane emission would probably also have been considerable. Here, we use a simple quantitative approach to estimate the magnitude of such methane production and show that the production of the greenhouse gas methane by sauropods could have been an important factor in warm Mesozoic climates.

If you read the story (full text here) you will find that the contention depends on many assumptions and rather extravagant extrapolation. The gassiest dinosaurs were the Sauropods which became abundant during the Jurassic Period about 150 million years ago. Global temperatures are estimated to have been 18 F warmer than today, but that warmth began in the preceding Triassic Period about 250 million years ago. There seems to be a timing problem. Also, the researchers estimate that the amount of methane produced by dinosaurs was similar to the amount produced today by livestock farming and industry, so why aren’t we warmer?

At the end of the paper, the researchers note as an attempted justification for their speculation:

 ”Although dinosaurs are unique in the large body sizes they achieved, there may have been other occasions in the past where animal-produced methane contributed substantially to global environmental gas composition: for example, it has been speculated that the extinction of megafauna coincident with human colonization of the Americas may be related to a reduction of atmospheric methane levels.”

That references a 2010 paper in which the researchers estimated the amount of methane produced by mammoths and other large herbivores. They speculate that the arrival of humans in North America and the subsequent disappearance of these animals reduced methane emissions and led to an abrupt cooling period, the Younger Dryas, about 12,800 years ago.

At the end of the Younger Dryas, the global temperatures and atmospheric methane both rose rapidly. So where did the methane come from since those flatulent mammoths were no more? The mammoth fart theory fails to explain previous similar abrupt cooling and warming in the Older Dryas period and the Oldest Dryas period, nor a subsequent similar event about 8,200 years ago.

Both of these papers present interesting stories, but they both fail upon close inspection. Still, science is speculative and the stories make headlines and get the authors published.

See also:

Arizona Geological History Chapter 5: Jurassic Time

Ice Ages and Glacial Epochs

Research Review 3 Climate cycles and a Mammoth Mystery

The PETM temperature spike caused global temperatures to get even warmer.  Drill core data from deep-sea sediments in the Atlantic and Pacific oceans suggested a rapid rise (geologically rapid, i.e., 10,000 years) of 5°C to 9°C (9-16°F) higher than the existing temperature prior to the event, that is, to as much as 34°F warmer than now.  Global temperature stayed at this elevated level for about 100,000 years, then rapidly cooled back to the prevailing normal temperature and then cooled even more.  Atmospheric carbon dioxide is estimated to have risen from the prevailing 1,000 ppm to about 1,700 ppm, more than four times higher than today.

The cause of the temperature spike is controversial.  Theories include volcanic eruption and massive forest fires that could have put large quantities of carbon dioxide into the atmosphere, changes in ocean circulation, and evolution of methane into the atmosphere.  Recent research shows that the amount of carbon dioxide in the atmosphere was insufficient to cause all of the temperature rise (Zeebe et al.), and that warming began before the rise of carbon dioxide (Secord et al.).

The current favored hypothesis is that methane (CH₄) was the primary cause of temperature rise.  Methane is a powerful greenhouse gas and its evolution into the atmosphere could have initiated warming.  Carbon dioxide is formed by reaction of methane with oxygen. Under warming conditions carbon dioxide also exsolves from the ocean. Evidence suggests that warming happened in several pulses.  However, once all the methane was destroyed by reaction with oxygen, the planet cooled in spite of there being copious carbon dioxide in the atmosphere.  This shows that the weak warming effect of carbon dioxide is easily overcome by other natural forces.

Where did the methane come from? Let me set the scene. At the time of PETM, the continents were not in their present location.  The North Atlantic was just beginning to open to the Arctic Ocean; this could have changed the ocean circulation and hence the sea temperature. Volcanism and other tectonic disturbances were very active as the Atlantic opened.

There are two potential sources for methane.  One is methane hydrates sequestered in ocean sediments.  Methane hydrates are ice-like compounds of water and methane formed under cold deep sea temperatures and pressure.  Either a change in temperature or a change in pressure would release the methane.

The second, a perhaps more likely source, involves volcanism and organic methane sequestered in deep sea sediments, similar to the oil shale deposits now being explored.  As noted in Geotimes (October 2006), research in the Norwegian sea found thousands of hydrothermal vent complexes that date to the Paleocene-Eocene boundary.  As methane-bearing sediments were subducted deeper and deeper, they came into contact with hot magma from the mantle.  This can cause explosive events and rapid release of methane.  This scenario is supported by the high ratio of Carbon-12 to Carbon-13, indicating microbic generated methane, found at the PETM event.

With rapid warming came both death and opportunity.  Mammal diversity and range exploded as did that for terrestrial plants. The North American horse first appeared at this time.  At the same time, however, deep-dwelling ocean fauna suffered a rapid extinction.

Although the global temperature dropped rapidly after PETM once the methane was used up, another warming spike happened about 40 million years ago in mid-Eocene time, possibly due to a similar cause.  But afterwards another sharp cooling trend began and by 34 million years ago ice began to form in Antarctica.  Global temperatures have been dropping ever since.   We are presently in an interglacial period of an ice age that began about three million years ago.

References:

Ross Secord, Philip D. Gingerich, Kyger C. Lohmann & Kenneth G. MacLeod, 2010, Continental warming preceding the Palaeocene–Eocene thermal maximum, Nature 467,955–958.

Richard E. Zeebe, James C. Zachos & Gerald R. Dickens, 2009, Carbon dioxide forcing alone insufficient to explain Palaeocene–Eocene Thermal Maximum warming, Nature Geoscience 2, 576 – 580 (2009)

See also:

Ice Ages and Glacial Epochs

Arizona Geologic History: Chapter 1, Precambrian Time When Arizona was at the South Pole

Arizona Geological History: Chapter 2, Cambrian and Ordovician Time

Arizona Geological History: Chapter 3: Devonian to Permian Time

Arizona Geological History Chapter 4: Triassic Period

Arizona Geological History Chapter 5: Jurassic Time

Arizona Geological History 6, The Cretaceous Period

Arizona Geological History 7: The Cenozoic Era

But there are environmental concerns. Most of those concerns are about possible contamination of groundwater from the drilling fluids. The Department of Energy has announced “Breakthrough Water Cleaning Technology Could Lessen Environmental Impacts from Shale Production.”

A private company, ABSMaterial, developed its Osorb® technology, which uses swelling silica material to remove impurities from the flow back water and produced water from hydraulically fractured oil and gas wells. Tests show that the silica removes “more than 99 percent of oil and grease, more than 90 percent of dissolved BTEX (benzene, toluene, ethylbenzene, and xylenes), and significant amounts of production chemicals.” Testing has shown that total petroleum hydrocarbon levels in the water were slashed from 227 milligrams per liter to 0.1 milligrams per liter. The silica material “a hybrid organic-inorganic nano-engineered structure, is a breakthrough in hydrocarbon removal technology that rapidly swells up to eight times its dried volume upon exposure to non-polar liquids. The swelling process is completely reversible—with no loss in swelling behavior even after repeated use—when absorbed species are evaporated by heating the material.”

Still, some media hypes anti-energy propaganda. Typical is the headline from an April 10 story in the Arizona Daily Star which read: “Water wells show contamination near gas-drilling sites.”

The story mentions “potentially dangerous concentrations of methane gas in water from wells near drilling sites in northeastern Pennsylvania…” Methane is non-toxic but can produce a fire hazard if concentrated. The Star story says that researchers from Duke University did not find any trace of chemicals used in the hydro-fracturing process.

Upon further reading we find, “The authors admit they have no baseline data at all, which makes it impossible to characterize the state of those water wells prior to recent development.” So we don’t know if nearby drilling caused “contamination” or if the presence of methane there is a natural phenomenon. The headline does not match the story.

The Arizona Daily Star has so far not mentioned the water cleaning technology. Does the Star practice content bias?

Update from a reader:

The chemist who first discovered Osorb and its unique properties, Dr. Paul Edmiston, grew up in Tucson. He is an a graduate of Salpointe High School, went to college at Pepperdine in California and returned to the U of A for his PhD.  He is now at College of Wooster in Ohio, He and his partner, Steve Spoonamore, are the founders of ABSMaterials.

Construction of the Rocky Mountains, volcanism, and emplacement of our major copper deposits, all of which began in Cretaceous time, continued in the Cenozoic until about 40 million years ago. During this time, the oceanic crust of the Pacific Ocean was being subducted beneath the westward-moving North American continental plate. The resulting compression caused southern and western Arizona to be topographically higher than the Colorado Plateau, the opposite of current topography.

By about 20 million years ago (mya) Arizona was covered with thousands of feet of volcanic rocks, locally punctured by calderas. Sometime between 30- and 20 million years ago the north American tectonic plate overrode a spreading center called the East Pacific Rise. This area is similar to the spreading center of the Mid-Atlantic ridge that gradually separated Africa from South American, and Europe from North America. Today, this western spreading center runs up the Gulf of California and separates Baja from mainland Mexico. It is also the driver of the San Andreas fault in California. By over-riding the spreading center, the tectonic regime changed from compression to extension. Arizona began to be pulled apart to form the Basin and Range physiography of today.

Arizona is divided into three physiographic provinces: the Colorado Plateau in the northeast, a transition zone extending from northwest to southeast Arizona (the Mogollon Rim), and the Basin and Range province in the south and west. Currently the Basin and Range extends from the Snake River plain in Idaho, through Nevada and Arizona, into Mexico.

Initially, crustal extension along a northeast-southwest axis was characterized by widespread normal faulting and fault-block rotation. Movement occurred along high-angle normal faults which at depth flattened into low-angle detachment faults (see figure below from Spencer and Reynolds). Displacement along these faults is several tens of kilometers. The present location of the Tucson Mountains is a direct result of this extension. (See Tucson Mountain Chaos) Later extension resulted in high-angle faults which bound our valleys and make some of the valleys as much as 15,000 feet deep to bedrock.

This extension sometimes made the life of geologists very interesting when exploring for porphyry copper deposits, because some of those deposits were cut and fanned out like a deck of cards. Finding all the pieces took some geologic detective work. For instance, the Twin Buttes mine, the Mission-Pima mine, and the San Xavier mine south of Tucson, together with buried mineralization between them, represent slices of a once-intact mineral deposit. The Sierrita mine, located on the opposite side of a major fault from the others is still intact.

Middle Cenozoic veins host gold, silver, and base-metal deposits. Copper-gold mineralization is associated with the detachment faults. Manganese and uranium deposits occur in the basins resulting from the extension.

Volcanic activity resumed 2- to 3 million years ago with eruption of basalt which produced flows and cinder cones. The rocks of the San Francisco volcanic field near Flagstaff, the Springerville-Show Low field, the San Bernardino field east of Douglas, and the Pinacate field in Mexico are examples of this episode.

The Grand Canyon was formed during the late Cenozoic. The Colorado River existed as long ago as 20 million years, but it flowed to the northeast across the Colorado Plateau. Crustal extension disrupted this flow pattern and caused the formation of several lakes similar to the Great Salt Lake (i.e., the lakes filled by interior flow from rivers that did not flow to the sea). As the Gulf of California opened, drainage into the Gulf gradually worked its way north and eventually “captured” the interior drainage of the Colorado River system. The lower river began its development about 5.5 mya; by 1.2 mya it was at its present grade in the western Grand Canyon.

Climate in the early Cenozoic continued to be hot and steamy, about 18 F warmer than today, even though atmospheric carbon dioxide had been decreasing for 80 million years due to coal formation in the Cretaceous. Around 55 mya, there was a sudden temperature spike that lasted for about 100,000 years. (That’s geologically sudden, i.e., 10,000 years to form.) The spike is known as the Paleocene-Eocene Thermal Maximum (PETM). Data, derived from drill cores brought up from the deep seabed in the Atlantic and Pacific Oceans, show that the surface temperature of the planet rose by as much as 15 F over the already warm temperatures. The cause is controversial.

Carbon dioxide levels rose from 1000 ppm to 1700 ppm–more than four times higher than today’s level of 385 ppm, but that rise began after the start of the temperature spike.

Isotopic analysis of carbon suggests that the culprit was methane, which is 65 times more powerful as a greenhouse gas than carbon dioxide. There are two hypothesis as to the source of methane: microbially generated methane buried in sediments along the slopes of the continental shelves; and methane clathrates. Methane clathrates are crystalline structures of methane bound to water. They form at near freezing temperatures under high pressure. They are stable up to 64 F under high enough pressure. This form of methane exists along our coasts today, frozen in the sediment at low temperatures and high pressures. They are being investigated as a source of energy.

It is speculated that volcanism and tectonic disturbance released pressure that was holding the methane in clathrates or in sediments themselves. This “sudden” release of methane caused the temperature spike. (There is nothing to prevent this from happening again.)

After that temperature spike subsided, temperatures remained warm until about 34 mya. At that point the Antarctic ice sheet began to form. Temperatures continued to drop. About 2.6 mya, continental ice formed at lower latitudes and initiated the glacial epochs and interglacial periods of our current ice age. (I will write in detail about our ice age and its cosmic connection in a future blog.)

See other chapters in this series:

Precambrian, Early Paleozoic, Late Paleozoic, Triassic, Jurassic, Cretaceous.

Throughout this series I have been using paleomap reconstructions of where continents have been. The continents are still moving. Here’s where the continents might be 50 million years from now.

See:

Ice Ages and Glacial Epochs

References:

Shellito, Cindy, 2006, Catastrophe and Opportunity in an Ancient Hot-House Climate, Geotimes, October 2006.

In Arizona Geological Society Digest 17:

Lucchitta, Ivo, 1989 History of the Grand Canyon and of the Colorado River in Arizona.

Lynch, D.J., 1989, Neogene volcanism in Arizona.

Menges, C. M., 1989, Late Cenozoic Tectonism in Arizona and its impact on regional landscape evolution.

Scarborough, R., 1989, Cenozoic erosion and sedimentation in Arizona.

Spencer, J.E. and Reynolds, S.J., 1989, Middle Tertiary tectonics of Arizona and adjacent areas.

Spencer, J.E., and Welty, J.W., 1989, Mid-Tertiary ore deposits in Arizona.