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Death of the Dinosaurs - K-Pg Boundary and Deccan Traps

Death of the Dinosaurs - K-Pg Boundary and Deccan Traps

Above: Front of the Specimen Card

The large-scale geological event known as the End-Cretaceous Mass Extinction had a profound influence on life on our planet. Three-quarters of all life on Earth perished during this time, from marine invertebrates like the ammonites, to the large avian and marine reptiles which had held their dominant place for so long, and of course the dinosaurs. In a geological instant, hundreds of non-avian dinosaur species, the product of more than 175,000,000 years of evolution, completely disappeared from the Earth.

The cause of this mass extinction event is an ongoing and often contentious debate in the scientific community. Did the extinction happen rapidly or was it the product of a long period of change in climate? Or perhaps the culmination of both factors?

Above: The Death of the Dinosaurs with K-Pg material and Deccan Traps remains.

As pictured above, this item includes the physical evidence behind the two leading theories for the death of the dinosaurs: the Chicxulub Asteroid Impact and the flood basalts of the Indian Subcontinent known as the Deccan Traps.

Above: Varied material from the Deccan Traps

The Deccan Traps is one of the largest volcanic features on earth. Stretching across the Indian Subcontinent, the remnants of these powerful flood basalts reach depths of more than 1.2 miles (2,000m). The eruption of the Deccan Traps came in relatively fast pulses just before the recognized boundary between the Cretaceous and Paleogene Periods (c. 66.8 million years ago). Sulphur-dioxide released by this eruption is thought to have cooled the planet by as much as 2°C (3.6°F), a data point which is reflected in the study of extinction rates in many smaller forms of life including foraminifera as well as larger species like the dinosaurs. The specimen in Age of Dinosaurs is a mixture of the portions of three distinct phases of the main eruption donated by Professor Gerta Keller of Princeton University. We are very grateful for Dr. Keller’s kind donation of this material which underlies a lifetime of work on this fascinating subject.

Above: K-Pg Boundary Material

By contrast, the Chicxulub Asteroid Impact (c. 66 million years ago) provides a dramatic exclamation point to the end of the Mesozoic. At a minimum, the Chicxulub impactor was 6 miles (9.6km) in diameter, and the energy released likely exceeded more than 100 million megatons. Evidence of massive fires and mega-tsunamis traced to this event have been found in many areas of the world, as well as a fine layer of the element Iridium which is known today as the K-Pg Boundary Layer. The discovery of this global layer and the eventual hypothesis is credited to Nobel Laureate Dr. Luis Alvarez and his son Dr. Walter Alvarez. The specimen in the Mini Museum is a mixture of the K-Pg Boundary Layer samples taken from across North America and Europe.

The specimens are housed in an acrylic jar that is encased within a glass-topped riker display box. The box measures 4 1/2" x 3 1/2". A small information card is also included, which serves as the certificate of authenticity.

Please Note: The distribution of the material in each specimen will be unique. Product images are representative samples. The approximate size for each specimen is 2 cm wide by 1 cm tall (e.g. twice the size of the specimen in Age of Dinosaurs).

The End of the Mesozoic

"To be a dinosaur is to belong to a staggeringly successful group of animals whose reign across time may never be matched by humans or any of our mammalian kin." ~ Dr. Kenneth Lacovara, discoverer of Dreadnoughtus schrani one of the largest known dinosaurs, "Why Dinosaurs Matter" (2017)

Few aspects of deep history fascinate humankind as much as the death of the dinosaurs. Even today, new revelations, such as Dr. Robert DePalma's discovery of mass kill sites that may literally capture the very day of the Chicxulub impact, can dominate world headlines for weeks. Exploration of these discoveries is also, in many ways, challenging moments for science.

Above: "The Tanis Konservat-Lagerstätte. (A) Plaster field jacket with partially prepared (freshwater) acipenseriform fish next to a nacreous ammonite shell. (B) Partial site map showing carcasses oriented by flow. (C) Field photo showing mass grave of fish carcasses, aligned by flow from "A seismically induced onshore surge deposit at the KPg boundary, North Dakota." by Robert DePalma (2019)

The current mainstream explanation for the mass extinction of the non-avian dinosaurs derives from a theory proposed in 1980 by the Nobel Prize-winning physicist Dr. Luis Alvarez, his son geologist Dr. Walter Alvarez, and several others. It is by all accounts the leading theory, but when it was released in 1980 it dropped on the establishment like a... well, like an asteroid colliding with the Earth.

Inspired by the presence of iridium—a metal rare in Earth’s crust but common in meteorites and the deep innards of planets—in the “boundary clay” layers found worldwide at the K-Pg transition, the Alvarez hypothesis suggested the massive impact of an extraterrestrial body—a bolide, in other words, an asteroid or comet—triggered the dinosaur-destroying extinction.

Above: Top: Shaded relief image of the northwest corner of Mexico's Yucatan Peninsula generated from Shuttle Radar Topography Mission (SRTM) data, and shows a subtle, but unmistakable, indication of the Chicxulub impact crater. Bottom: Same area viewed by the Landsat satellite, and was made by displaying the Thematic Mapper's Band 7 (mid-infrared), Band 4 (near-infrared) and Band 2 (green) as red, green and blue. (Source: NASA 2003)

In the 1990s, this theory was buoyed by the discovery of the nearly 200-mile-wide Chicxulub crater along the northern Yucatan coast of Mexico, which roughly matches the 66-million-years-ago timestamp of the K-Pg extinction event. In the decades since, numerous panels have reviewed calculations, samples, and methods and most have come to the conclusion that the Alvarez theory must be correct and exclusive.

Above: Luis (left) and Walter Alvarez at the K-Pg Boundary in Gubbio, Italy 1981. (Source: Lawrence Berkeley Lab Archives)

Certainly, there is no doubt that a massive object collided with the Earth at the end of the Cretaceous. The latest research on the Chicxulub also suggests that the location of the primary impact was especially devastating. Sulfur aerosols released in mass quantities would make the atmosphere toxic and rapid ocean acidification due to increased carbon would mean death for marine species as well.

Yet if we've learned anything about life during the exploration of billions of years of history, it is that it is resilient in the face of overwhelming natural disasters. It really does find a way, at least in the short term. What truly impacts life on a grand scale is the march of time itself; the shifting of continents for example, and the large-scale effects of long-term climate change.

Not long before the Alvarez team presented their impact hypothesis in 1980, paleontologist Dewey McLean had suggested the end-Cretaceous mass extinction was caused by a series of enormous volcanic eruptions that built the flood-basalt province of the Indian subcontinent known as the Deccan Traps.

Though the Deccan Traps theory has been majorly overshadowed by the impact hypothesis essentially since the latter’s inception, it’s had a fierce proponent for decades in the form of the Princeton University Professor of Geosciences Dr. Gerta Keller.

Above: Dr. Gerta Keller at Princeton with an Allosaurus unearthed in 1941. (Source: Princeton Alumni Weekly Photographer: Peter Murphy)

Based on Dr. Keller's work with the unicellular marine organisms called foraminifera (or “forams,” for short)—which have left behind such an abundant and long-term fossil record that they’re something of a benchmark for tracking broader evolutionary trends—Keller contends the hundreds of thousands of years of Deccan Traps basalt floods were the primary driver of the K-Pg extinctions, not a bolide impact.

Above: Late Campanian–Maastrichtian faunal and floral turnover. Note the rapid increase in species richness in all groups in the late early Maastrichtian, except for inoceramids and rudistids, which decreased and went extinct. Planktic foraminifera reached maximum Cretaceous diversity. The terminal decrease in all groups began during the last 500 ky of the Maastrichtian. (Source: Keller, Abramovich, 2003)

Like the Alvarez theory, Keller's work has a basis in a massive data set. For decades she and others tracked the gradual diminishment in foram vigor and diversity across 300,000 years before and after the K-Pg boundary. The data suggests that the drastic global impacts of the prolonged Deccan Traps eruptions—acid rain resulting from the basalt floods’ sulfur, global warming-induced by their carbon dioxide and methane, rains of ash, lead, and mercury, and the like—upturned ecosystems and spelled the demise of much of life on Earth, but in a more drawn-out fashion than the sudden space-rock annihilation favored by impact theorists.

Above: "The effects of increasing environmental stress upon planktic foraminiferal assemblages from optimum to catastrophe conditions show the successive elimination of large, specialized k-strategy species, the survival of small r-strategy species, the overall dwarfing of these species and their great abundance. All of these factors characterize the Lilliput effect. (Source: Keller, Abramovich, 2003)

Other major flood-basalt eruptions seem to correspond with older mass extinctions: The Siberian Traps, for instance—among the largest-known flood-basalt provinces—may have contributed to the devastating End-Permian Extinction (the “Great Dying”), the worst of all.

Keller also sees plenty of sobering modern relevance in the idea of the Deccan lavas’ atmospheric impacts orchestrating a great global die-off, given the current state of the human-caused climate change. In a 2018 interview in The Atlantic, she said, “You just replace Deccan volcanism’s effect with today’s fossil-fuel burning. It’s exactly the same.”

The purpose of this discussion is not to settle the debate or to cast doubt on either theory, but rather to give a moment's pause here at the end of the Mesozoic Era. No matter which theory is correct, or even if they are both wrong or right together, what we know for certain is that one of the most successful groups of animals in the history of our planet perished along with so many other species and families.

Now, millions of years removed, we too face a moment of intense challenge. The signs are all around us. How do we act? What do we do to avoid a similar fate? How do we treat each other now, and what world do we hand to generations yet to come by our actions in the present?

These questions are things to think about as you look at the Age of Dinosaurs and think about all of the magnificent creatures and geological wonders we have explored together. 

Further Reading

DePalma, Robert A., et al. "A seismically induced onshore surge deposit at the KPg boundary, North Dakota." Proceedings of the National Academy of Sciences 116.17 (2019): 8190-8199.

Poling, Devereaux A., and E. Margaret Evans. "Are dinosaurs the rule or the exception?: Developing concepts of death and extinction." Cognitive Development 19.3 (2004): 363-383.

Keller, Gerta, and Sigal Abramovich. "Lilliput effect in late Maastrichtian planktic foraminifera: Response to environmental stress." Palaeogeography, Palaeoclimatology, Palaeoecology 284.1-2 (2009): 47-62.

Thomson, Keith Stewart. "Marginalia: Dinosaurs as a cultural phenomenon." American scientist 93.3 (2005): 212-214.

Brennan, Peter. “The ends of the world: Volcanic apocalypses, lethal oceans, and our quest to understand Earth's past mass extinctions.“ Harper Collins, (2017), 309 pp.

Lacovara, Kenneth. “Why dinosaurs matter.” Simon and Schuster, (2017), 163 pp.

Achenbach, Joel. “The Dissenter.” Princeton Alumni Weekly, 6 June 2012.

Bosker, Bianca. “The Nastiest Feud in Science.” The Atlantic, 7 September 2018.

Above: The back of the Specimen Card.

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