Stegodon: Does this ancient elephant have origins in Asia?

So much has been said in recent years about the wealth of fossils in China. Almost all of it about dinosaurs: exciting new species, feathered fossils, nest upon nest of dinosaur eggs.  There is no doubt that China holds exciting clues to the history of our planet; one has only to wait to hear of the next discovery.

Within the past few months, yet another exciting find was revealed, but this time about a little known mammalian ancestor: Stegodon.

 

Stegodon by artist Hannah Stephens

Painting of a Stegodon by artist Hannah Stephenshannahleestudio.com.

 

The name Stegodon, to me, evokes ‘dinosaur’, not ‘mammal,’ but this was, indeed, an ancient animal.  Its fossils resemble those of other similar mammals, from mastodons to mammoths to today’s elephants.

 

 

Alexandra van der Geer - shrinking elephants

Figure 1: Reconstruction of four insular dwarf proboscideans with their respective mainland ancestors. Mainland proboscideans: 1, Palaeoloxodon antiquus; 2, Mammuthus columbi; 3, Stegodon zdanskyi [stegodon found in China]. Insular proboscideans: 4, Palaeoloxodon ‘mnaidriensis’; 5, Palaeoloxodon falconeri; 6, Mammuthus exilis; 7, Stegodon aurorae [a type of dwarf stegodon found in Japan]. Based on skeletons at Museo di Paleontología, University of Rome, Italy (1), American Museum of Natural History, New York (2), Taylor Made Fossils, U.S. (3), Museo di Paleontología e Geología G.G. Gemmellaro, Palermo, Italy (4), Forschungsinstitut und Naturmuseum Senckenberg, Frankfurt, Germany (5), Santa Barbara Museum of Natural History, Santa Barbara, U.S. (6), Taga Town Museum, Honshu, Japan (7). Photos 1–2, 4–7 George Lyras, photo 3 courtesy of TaylorMadeFossils.com, reproduced here with permission.

From The effect of area and isolation on insular dwarf proboscidea by Alexandra A. E. van der Geer et al; photo and caption courtesy of Dr. Alexandra van der Geer.

 

When Stegodon skulls with tusks attached have been found, many (but not all) of the tusks are close together–preventing the trunk (the ‘proboscis,’ from which this group gets its name; proboscis —> proboscidea) from hanging between them.

They lived in what is now Africa and Asia, causing continued debate over its place of origin. Until recently, the oldest known Stegodon fossil, a 6.5+ million-year-old partial molar from Kenya, was described by William J. Sanders in 1999.  That record changed this past December when Dr. Hong Ao and his colleagues published their results dating the sediment in the Lanzhou Basin, China, from which a number of fossils–including that of a Stegodon–were found.

And that Stegodon was found to be between 8 – 11 million years old.

 

GSA Geologic Time Scale - Neogene

Detail of the Geologic Time Scale, created by the Geological Society of America.  Stegodon is believed to have existed between the Miocene to the Pleistocene, a relatively small segment of time in Earth’s overall history, but still considerably longer than that of our own species!  (You can view the time scale in much better detail here.) 

 

The fossils of the Stegodon, along with at least 5 other species, were actually found in the 1980s by Professor Xing Zhang of Northwest University in China.  Given the length of time between the fossil excavations and the recent dating of these fossils, one might wonder why determining the fossil age took so long.

Dr. Ao, a scientist at the State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, and his colleagues state that western China does not have suitable material for radiometric dating, an oft-used method for this purpose.

When I asked why this was so, Dr. Ao replied by email, “Because volcanic activities are rare in western China during the late Cenozoic, it is difficult to find  in situ tephros or tuffs for radiometric dating (e.g., 40Ar/39Ar dating).”

Instead, they conducted a magnetostratigraphic study, one in which they determined the age of the rock through the polar reversal record.  Combining this with analysis of the fossils provided evidence that this Stegodon is 2 – 5 million years older than that of the Kenyan partial molar.

“We are indeed surprised by our dating results,” Dr. Ao continued, “which document that the Lanzhou Stegodon is the oldest Stegodon worldwide, although the Stegodon  fossil [was] not discovered by us. However, our dating results document it to be the oldest known Stegodon fossil.”

Dr. Hong Ao 1

 

Dr. Hong Ao 2

Dr. Hong Ao 3

Dr. Hong Ao 4

Images of Professor Yongxiang Li (from Northwest University) and his master student as well as several employed workers who helped to excavate mammal fossils, Lanzhou Basin, China; photos courtesy of Dr. Hong Ao.

 

indricotherine fossil

indricotherine fossil2

indricotherine fossil3

Images of indricotherine fossils found in Lanzhou Basin, China; photos courtesy of Dr. Hong Ao.

 

Dr. Ao himself has been working with fossils in the Lanzhou Basin for 5 years.  When asked how  he and his co-authors chose to work together on this recent paper, he wrote, “I have collaborated with them on broad subjects before, thus I [invited] them to join [in] this research.”

Finding information about this extinct species is difficult.  Unlike mammoths or mastodons, Stegodon does not appear to be a popular ancient animal.

Fortunately, Dr. Alexandra van der Geer–paleontologist, indologist, ethno-zoologist and author –has not only studied this species, she very generously made herself available for questions.  Currently, Dr. van der Geer is an Associate Researcher at both the National and Kapodistrian University of Athens and the Naturalis Biodiversity Center in the Netherlands. She is part of the Isolario project, a project that studies biodiversity and cultural evolution within an island context.

When I asked why there was such a dearth of information on Stegodon, she wrote, “We can think of several reasons for this.”

“First of all, stegodons typically are the elephants of Southeast and East Asia, where most countries did not have the resources and opportunities most Western countries had when it comes to scientific research and excavations. These activities are costly, and since they don’t have a direct use in the sense that they don’t advance the medical, technical or economic levels of a country, they have, understandably, a lower priority. Furthermore, because of this region, half the publications (especially before the 1990s or so) you can find are in Chinese or Japanese, which is not very helpful to the [English-speaking] world.

“Secondly, stegodons are forest elephants. Forest areas are very unlikely places for the long-term preservation of organic materials: everything is eaten, digested or otherwise broken down into smaller components in no time. The tropical (warm, humid) climate of these forests is not helpful either, as decomposition is much faster here. Stegodon remains only have a chance to be preserved when (1) they are covered fast, such as with river sediments, volcanic ashes etc., (2) or are in an oxygen-free environment, such as sunken deeply into a swamp, (3) or were deposited in a natural fridge such as limestone caves where they are gradually covered in clayish sediment or [travertines]. The same is valid for Palaeoloxodon, the Old World fossil elephant, but Europe has many limestone caves, which are excellent for preservation (for a nice [travertine]-preserved negative skull, see Stuttgart museum: skull cast SMNS nr. 32888 from Bad Cannstatt).

“As you can deduct from these preservation issues, it is more likely to find molars and tusks than skeletal material, which is much softer. The vast majority of proboscidean findings all over the planet consists of molars and tusks, and that is not for nothing. Inherently this means that there is much more information about their dentition and diet than about their bodies.”

I was interested in understanding why Stegodons are portrayed as hairless animals, so very similar to contemporary elephants.  Was this just an artistic guess?

“The hairlessness of stegodons is not an artistic guess but a scientific guess instead,” Dr. van der Geer answered.  “Very large animals with thick skins (pachyderms) in a (sub)tropical environment are unlikely to have a significant hair covering. Elephants lost their hairs secondarily. The information for hair growth is not lost, and baby elephants still have a thin, woolly coat. Woolly mammoths lived in the cold, temperate zones, and needed hair, so they were covered in a thick layer of hairs, and for this is evidence (mummies preserved in the permafrost), but the other mammoths (M. meridionalis, M. columbi, M. exilis, etc.), [did] not, and it’s generally assumed that they had a light coat fitting to the temperate zones.

“Tropical and subtropical stegodons almost certainly did not have any coat that’s worth mentioning. Stegodons of temperate zones, however, may have been more hairy. Indeed, the lack of hairs makes them look more like today’s elephants.”

 

Alexandra van der Geer - Stegodon ganesa-model-I.Vjdchauhan-SiwalikHills

Photo of the two life-size models of Stegodon ganesa;photo courtesy of Dr. Gerrit van den Bergh (University of Woolongong, Australia); special thanks to Dr. Alexandra van der Geer.

 

“Note, however, that the proboscis is carried very differently. Their tusks are set very close to each other, so the proboscis doesn’t fit in between as in modern elephants, Asian and African alike. This means that the mobility of their proboscis was more restricted, relative to their living relatives.”

 

Alexandra van der Geer - Flores-excavation-31-stegodon-florensis

Fossils of Stegodon florensis insularis, from Flores, Indonesia; photo courtesy of Dr. John de Vos (Naturalis, the Netherlands); special thanks to Dr. Alexandra van der Geer.

 

Alexandra van der Geer - stegodon-timorensis-mandible

Mandible (and holotype!) of  Stegodon timorensis; photo courtesy of Eelco Kruidenier (Naturalis, the Netherlands); special thanks to Dr. Alexandra van der Geer.  Anyone familiar with proboscidean teeth and jaws will recognize the similarities instantly.

 

But how do we know that Stegodon–a rather enormous animal–evolved into something smaller?

“[D]warfs and giants are relative. Something can be a dwarf, yet have a considerable size. When we speak of dwarf stegodons, we mean stegodons that are much smaller than their ancestors. For this, you have of course to have identical or otherwise similar elements from both the descendant and the ancestor in order to compare reliably,” she continued.

“The expectation is that dwarf stegodons must have existed on the islands, following the so-called island rule, according to which large animals get smaller in isolation. There is sound evidence that this rule still stands, and is even more pronounced for fossil species (see Lomolino et al., 2013, in Journal of Biogeography).

“Indeed, the many fossil molars from the Southeast Asian islands (‘Wallacea’) are all much and much smaller than the same molars from their mainland ancestors (see Van den Bergh, 1999). True, you first have to know what is the ancestor, and for this you need information about morphology, or how the molars, tusks, skulls and postcranial elements look like. After that, you compare the sizes.

“Note that if a molar is, for example, half the length of the same molar of its ancestral species, the body weight of that animal must have been a quarter of that of its ancestor! (the cubic law: linear reduction 50% means volume reduction 50% of 50%).”

Alexandra van der Geer - Flores-stegodon-florensis

Molar of Stegodon florensis; photo courtesy of Dr. Gerrit van den Bergh (University of Woolongong, Australia); special thanks to Dr. Alexandra van der Geer.  

 

“The most interesting dwarf stegodon is Stegodon sondaari, named after the Dutch palaeontologist Paul Yves Sondaar (1934-2003), expert in fossil insular mammals. This stegodon lived on the island of Flores about a million years ago, and weighted only about 15% of the weight of its ancestral species, S. elephantoides (see Van der Geer et al., 2016, in Journal of Biogeography, doi:10.1111/jbi.12743).

“Sondaar’s dwarf stegodon is not the smallest stegodon, that honour goes to the Sumba stegodon (S. sumbaensis), of only 8% of the original weight. Sondaar’s stegodon is interesting because it may have witnessed the arrival of early humans, possibly the ancestors of the Hobbit, or Homo floresiensis. Its fossils are contemporaneous with primitive lithic artefacts, dated to about a million years ago (see Brumm et al., 2010, in Nature 464, pp. 748–752).”

 

Alexandra van der Geer - Sumba-stegodon-sompoensis-holotype-in-Naturalis-Leiden-2

Molar (and holotype!) of Stegodon sompoenisphoto courtesy of Dr. Gerrit van den Bergh (University of Woolongong, Australia); special thanks to Dr. Alexandra van der Geer.  

 

“[R]ecently,” she concluded, “one of the island dwarf stegodons (S. timorensis of Timor) has been dated to about 130 thousand years ago (see Louys et al., 2016, in PeerJ 4:e1788). This excludes, according to the authors, an anthropogenic cause for its extinction, because humans had not yet arrived at the island.”

 

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So many people helped with this blog post!  (But please remember that any errors are my own.)

Many, many thanks to Dr. Hong Ao (Dr. Ao Hong) from the State Key Laboratory of Loess and Quaternary Geology (Chinese Academy of Sciences) for his fascinating responses and the great images of fossil excavations in the Lanzhou Basin.  I am thrilled that he was willing to answer questions about his research and that of his colleagues! It was a great honor and a pleasure connecting with him!

I am indebted to Dr. Alexandra Van der Geer, who very kindly (and so very quickly–despite everything else she has going on!!) answered specific questions about Stegodon that I could not find anywhere else and who provided pictures of dwarf Stegodon fossils.  It was an equally great honor and pleasure connecting with her!

A mastodon-sized thank you to the amazing Dr. Katy Smith for providing needed and hard-to-find material on Stegodon fossils!

And an enormous thank you to artist Hannah Stephens for her depiction of a Stegodon as it may have appeared in life.  I am particularly moved by the warmth of its intelligent-looking eyes, and I love the tones within its skin.  I adore this picture.  I am grateful to have it in this post;  I am thrilled to have the actual painting hanging on my wall!  Please be sure to check out her artwork at: http://hannahleestudio.com or http://hstephens.blogspot.com

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References from Dr. Alexandra Van der Geer:

  1. Brumm A, Jensen GM, van den Bergh GD, Morwood MJ, Kurniawan I, Aziz F, Storey M (2010) Hominins on Flores, Indonesia, by one million years ago. Nature 464, 748–752.
  2. Lomolino MV, van der Geer AAE, Lyras GA, Palombo MR, Sax DF, Rozzi R (2013) Of mice and mammoths: generality and antiquity of the island rule. Journal of Biogeography 40, 1427–1439.
  3. Louys J, Price GJ, O’Connor S. (2016) Direct dating of Pleistocene stegodon from Timor Island, East Nusa Tenggara. PeerJ 4:e1788
  4. van den Bergh GD (1999) The Late Neogene elephantoidbearing faunas of Indonesia and their palaeozoogeographic implications; a study of the terrestrial faunal succession of Sulawesi, Flores and Java, including evidence for early hominid dispersal east of Wallace’s line. Scripta Geologica 117, 1–419.
  5. van der Geer AAE, van den Bergh GD, Lyras GA, Prasetyo UW, Due RA, Setiyabudi E, Drinia H (2016) The effect of area and isolation on insular dwarf proboscideans. Journal of Biogeography, doi: 10.111/jbi.12743

References used in this blog post:

  1. New magnetochronology of Late Miocene mammal fauna, NE Tibetan Plateau, China: Mammal migration and paleoenvironments; by Hong Ao, Peng Zhang, Mark J. Dekkers, Andrew P. Roberts, Zhisheng An, Yongxiang Li, Fengyan Lu, Shan Lin, Xingwen Li; Earth and Planetary Science Letters; 1o December 2015
  2. Oldest record of Stegodon (Mammalia: Proboscidea); by William J. Sanders; Journal of Vertebrate Paleontology; Vol. 19, No. 4, Dec. 13, 1999, pp. 793 – 797
  3. Fossil elephantoids, Awash paleolake basins, and the Afar triple junction, Ethiopia; by Jon E. Kalb; Palaeogeography, Palaeoclimatology, Palaeoecology; 1995, pp. 357 – 368
  4. The effect of area and isolation on insular dwarf proboscidea; by Alexandra A. E. van der Geer, Gerrit D. van den Bergh, George A. Lyras, Unggul W. Prasetyo, Rokus Awe Due, Erick Setiyabudi, and Hara Drinia; Journal of Biogeography; 11 March 2016.
  5. Magnetostratigraphy – concepts, definitions, and applications, by Cor G. Langereis, Wout Krijgsman, Giovanni Muttoni, and Manfred Menning; Newsletter on Stratigraphy, Vol. 43/3: 207–233, April 2010
  6. Mammoths and Mastodons of the Ice Age, by Adrian Lister, Firefly Books, 2014
  7. Mammoths, by Adrian Lister and Paul Bahn, University of California Press, 2007
  8. The Proboscidea: Evolution and Palaeoecology of Elephants and Their Relatives, Edited by Jeheskiel Shoshani and Pascal Tassy, Oxford Science Publications, 1996
  • Stegodontidae: evolutionary relationships by Haruo Saegusa, pp. 178 – 190, The Proboscidea: Evolution and Palaeoecology of Elephants and Their Relatives
  • Palaeobiogeography of late Neogene African and Eurasian Elephantoidea by Jon E. Kalb, David J. Froehlich, and Gordon L. Bell, pp. 117 – 123, The Proboscidea: Evolution and Palaeoecology of Elephants and Their Relatives
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Fossil Landscape Revealed: Reading the Rocks in New England Summits

It’s remarkable to think that we are discovering ice on a dwarf planet 4.67 billion miles (7.5 billion kilometers) away from Earth, at a time when we are still unraveling clues to the ice that once shaped this planet.

Two New England geologists have spent years studying the rocks and traces left by ancient glaciers in the White Mountains, the northern stretch of the Appalachian Mountains in New Hampshire and Maine. This past October, they co-authored a paper in Geology with 3 other scientists.  And in it, they revealed that the highest summits in New England were covered by solid ice during the Last Glacial Maximum.

 

View from the summit of Mount Moriah in New Hampshire looking at the White Mountains’ Presidential Range; image by Cappi Thompson at Getty Images.

 

But what does this mean? And why should we care?

“This question about whether or not the New England summits were covered by an ice sheet is long standing, going back over 100 years,” explained Dr. P. Thom Davis by phone.  “And one reason this question is important is because continental ice sheets take a long time to build up, and as they build up, they reduce global sea level.   So ice sheet thickness has implications far beyond just New England.”

Dr. Thom Davis of Bentley University and Dr. Paul Bierman of the University of Vermont actually wrote and presented the paper at the annual Geological Society of America conference in 1999, but they didn’t publish it until 2015.

“We sent a draft around informally to some colleagues,” said Dr. Davis, “and they sort of were giving us a hard time, wanting us to go back and rethink a lot of the implications. And then one thing led to another, and we just kept rethinking and rethinking for the next 15 years.”

“It was a much more radical proposition in 1999 than it is today,” explained Dr. Bierman. “Since then a whole lot of work has come out of the Arctic. So when we finally submitted this now, I guess it was a surprise, but it wasn’t unexpected.”

That ‘radical proposition’ involved whether or not ice covered the mountains, whether it was a certain type of ice, and therefore whether it did or did not preserve “fossil” or “relic” landscapes.   These ideas have been pondered (or dismissed) by various geologists since the mid 1800s.

While the term “fossil landscape” might inspire images of preserved prehistoric environments suffused with traces of ancient life, this is not at all what it means.  Rather, it refers to the geology left behind by cold-based ice–ice frozen all of the way to the ground–that both shielded rocks from the effects of cosmic rays and slowed erosion.

Think of how much impact an enormous sheet of ice can have on an environment.  When ice is not completely frozen to the ground (warm-based ice), water runs through it, pulling dirt, rocks–and the glacier itself!–along with it.  The ground erodes; the debris is carried elsewhere. Remnants can be seen in boulders scattered throughout New England.

Notice the shape of the valley in Crawford Notch, NH.  This valley is a result of glacier ice moving through the environment, albeit at a remarkably slow speed. Image by Mark Zelasko at Getty Images.

Boulder in Salisbury, NH

 

Detail of boulder in Salisbury, NH

Images of a boulder (perhaps a glacial erratic: a rock carried by a glacier and deposited in another location in geologic terms) in Salisbury, NH; photos taken by the author

 

“The word ‘fossil landscape’ sort of worried me from the get-go because of how it might be misconstrued to having more of a biological context, like mammoth bones,” stated Dr. Davis, in reference to the press release describing their work. “We’re looking at the age of exposure, the length of time those surfaces have been exposed to the cosmic ray bombardment.”

Drs Davis and Bierman collected samples near to or on the summits of Mt. Katahdin in Maine and Mt. Washington and Little Haystack Mountain in NH during the 1990s.  Their ‘radical’ suspicion–that these summits were indeed covered by solid ice–could only able be proven recently with advanced technology.

Before that, they–like their peers in the last two centuries–relied on visible clues: the type of rock on summits and in valleys, striations (or grooves) in the rocks that may have been made by  ice, the type of sediment in the valleys and whether this indicated the type of glacier that might have helped create them.  And one of the biggest clues?

Erratics.

“That is,” Dr. Davis explained, “stones that have been transported from another location.”

“Two centuries ago, scientists might have argued [that erratics] were deposited in these high locations by great floods,” he continued. “But that pretty much ended with Agassiz’s glacial theory in the middle of the 1800s.”

He is referring to Louis Agassiz, an eminent Swiss biologist and geologist who taught at Harvard, and perhaps the first to support the idea that these summits were covered by an ice sheet.  It is important to note, however, that he believed that ice sheet was a local glacier rather than a vast continental ice sheet.

Prior to this, geologists such as Charles T. Jackson–the first NH State Geologist–or Edward Hitchcock (of trace fossil fame) believed that a flood complete with icebergs was responsible for misplaced boulders. Striations could be explained by the force of rock against rock from powerful currents within that water.

British citizens Mary Horner Lyell and her husband, Charles–another well-known geologist from the 1800s–explored these mountains in 1845, including a trip up Mt. Washington on horseback. Lyell attributed erratics to melting icebergs.

Frozen tower and communication equipment at the summit of Mt. Washington; image by Onfokus at Getty Images.  Charles Hitchcock — son of Edward and Orra Hitchcock — helped create this year-round weather station.  He was a NH State Geologist and a Dartmouth professor. 

NH geology took a step forward with James W. Goldthwait and then later his son, Richard, in the 1900s.  They proposed that New England summits were covered by solid ice–not warm-based ice–and by a continental–not a local–ice sheet.

“[James W. and Richard P. Goldthwait] recognized this importance long ago, from the turn of the last century,” said Dr. Davis. ‘They both recognized very fresh looking erratics. The only way erratics can arrive on these summits is by continental ice sheets.”

“They made a really good case that the last ice sheet that dropped these erratics on the summits happened during our last glaciation about 20,000 years ago. [I]f the summits had been nunataks during the last major glaciation about 20,000 years ago, then the erratics should have been more weathered, the soils should have been more developed on the summit areas, and the bedrock should have been more weathered, as well.”

Baxter Peak of Mount Katahdin in Baxter State Park, Maine. View from Knife Edge Trail; image by Posnov at Getty Images.

Mount Katahdin is the highest mountain in Maine at 5,268 feet (1,606 m). Katahdin is the centerpiece of Baxter State Park: a steep, tall mountain formed from underground magma; image by Simon Massicotte at Getty Images.

The debate about the type of ancient ice in the White Mountains was dropped for a few decades, slowly regaining interest in the 1970s.  But it wasn’t until the recent paper by Drs. Bierman and Davis that proof lent itself to solving the issue.

“[Our method was to] count the abundance of very, very rare isotopes,” Dr. Bierman explained, “And, by that we mean isotopes of the element beryllium and the element aluminum.”

“The beryllium isotope with a total mass of 9 is the normal stuff that you find in nature. The beryllium isotope with a total mass of 10 per atom is extremely rare. And in order to measure these isotopes, we needed the technical ability to do that, and that didn’t come about until the late 1970s with a device called the accelerator mass spectrometer. These are very large, very expensive, difficult to maintain, and rare beasts. Over the past 30 years, they’ve been used increasingly by geologists to make the kinds of measurements that we did.”

“We also used cosmogenic carbon-14,” he continued, “which is an isotope with a much shorter half-life, about 5,730 years. And what that means is that when a rock is exposed to cosmic rays at the surface and then buried, that carbon 14 disappears much more rapidly than beryllium 10 and aluminum 26 isotopes.

“[Data from the accelerator mass spectrometer] tells us the [exposure] age because we can count the number of carbon-14 atoms, just like we can count the beryllium-10 atoms. We know that these are produced at a certain rate every year. It’s a very low rate.

“For beryllium-10, it’s just a few atoms per year per gram of material that we’re measuring. It’s a little bit more for carbon-14.  And since we know how quickly they’re made and we can count how many atoms there are, we can calculate an age–or a residence time–near the surface.”

“A lot of these ages from our exposure dating,” added Dr. Davis, “were coming out much older than we expected, much older than the last glaciation from the summits of both Katahdin and Mt. Washington.”

 


A view of Mt Washington and Mt Madison along some farmland in Shelburne, New Hampshire during winter; image by Cappi Thompson at Getty Images.

“I think the Goldthwaits were primarily looking at these kinds of qualitative data, like how fresh the erratics in the bedrock were,” Dr. Davis offered. “And based on that, they probably weren’t exposed very long.  But as it turns out, weathering varies dramatically to different latitudes, so is not a very quantitative method. That’s all we had, though, until these cosmogenic radionuclides became available for measuring.”

“The main point of our geology paper is that, apparently, even at temperate latitudes, the higher elevations may have been overrun by ice sheets that were frozen to the bed, leaving what we call ‘relic landscapes,'” he concluded.

“From a geologic point of view,” Dr. Bierman continued, “it points to the complexity of the evolution of the New England landscape. It’s another piece of the puzzle in how this landscape evolved over time.”

 


Sunrise clouds above the White Mountains’ Presidential Range in Jefferson, New Hampshire; image by Cappi Thompson at Getty Images.

Old_Man_of_the_Mountain_4-26-03

 

Old Man of the Mountain–an iconic NH rock formation, one that seems appropriate to share in a blog post on geology–on April 26, 2003, seven days before the rocks of its face collapsed. A late spring snow fell the night before. Image by Jeffrey Joseph, public domain, Wikipedia.

Dr. P. Thom Davis and Dr. Paul Bierman not only introduced me to a new science, they also piqued my interest in it. Basic geologic vocabulary was foreign to me. I delighted in discovering the meaning behind new words (nunataks, moraines, varve records, basal thermal regime!) in order to better understand their work. Thanks to their time and their research, I now look at the world around me with much more discerning eyes, especially at the many boulders erratics that scatter the landscape.  Fossils in New England may be scarce, but rock formations are not.  I extend a sincere and resounding THANK YOU to both, for their help, their graciousness and the fun three-way conversation we had discussing their paper!

Thank you to Kea Giles at the Geological Society of America for sending me a copy of the paper!

I highly recommend the book “The Geology of New Hampshire’s White Mountains” shown below, co-authored by Dr. P. Thom Davis. It is a fascinating account of NH geology and a great introduction to geology itself.

Woodrow Thompson, another co-author of that book, wrote an engaging account of the history of NH geology (paper is listed below). It was a great help to me in writing this piece, and I encourage anyone interested to read it

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References:

  1. Fossil Landscapes in New England, GSA press release, October 26, 2015
  2. Cold-based Laurentide ice covered New England’s highest summits during the Last Glacial Maximum, Paul R. Bierman, P. Thompson Davis, Lee B. Corbett, Nathaniel A. Lifton, Robert C. Finkel, Geology, October 2015
  3. History of Research on Glaciation in the White Mountains, New Hampshire (U.S.A.), Woodrow B. Thompson, Géographie physique et Quaternaire, Volume 53, 1999
  4. The Geology of New Hampshire’s White Mountains, J. Dykstra Eusden, Woodrow B. Thompson, Brian K. Fowler, P. Thom Davis, Wallace A. Bothner, Richard A. Boisvert, John W. Creasy; Durand Press, 2013

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