During the 14th century, the Inca ruler Inca Pachacuteq (Tito Cusi Inca Yupanqui) transformed the central Andean area of present-day Cusco, Peru into a major urban center. The city became the capital of the Inca empire, containing religious and administrative areas that were surrounded by fertile agricultural expanses. In the 16th century, the Spanish conquered Cusco, building their Baroque churches and palaces atop the remnants of the Inca city. Today about half a million people live in Cusco. The city is now known for its amazing indigenous population and as a mecca for tourists that travel on to the Sacred Valley and Machu Picchu.
Cusco Historic District
Cusco was declared a UNESCO World Heritage site in 1983 and the boundary for the site is mostly what is known as the Historic District (link here for a map of the UNESCO inscribed property). I did tour some of the buildings within the Historic District, my favorite being the Convent of Santo Domingo. The Spanish built this church on the remains of Qurikancha, a revered Incan temple for the Sun God Inti. The Inca stonework is the foundation for the cathedral and it is truly enthralling to see. Interestingly, numerous earthquakes have extensively damaged the cathedral, but the Inca stone walls still stand largely undamaged.
The Vino Canchón Market
The markets of Cusco – now they are an experience that can’t be missed. If you love food, Vino Canchón in the district of San Geronimo, is the place to go. This is the largest market in Cusco, supplying families as well as businesses with all kinds of produce, hardware, flowers, and many other items. It is also a market where the traditional Quechua language dominates the conversations. The Vino Canchón market is open daily and vendors are happy to talk with customers and the inquiring tourist.
Saqsaywaman and Its Geologic Puzzle
Saqsaywaman is the ruins of a fortified complex located at the northern edge of Cusco, on a hilltop that overlooks the city. As briefly summarized by Lake and others (2012):
“Most of the complex was demolished by Spanish settlers, who used the Incan stone to rebuild Cusco into a Spanish colonial town. What remains of the Saqsaywaman complex are large limestone blocks along with some shales, plasters and limonites which were too large for the Spanish settlers to easily remove. Some of these blocks are over 125 tonnes. Chroniclers state, that the construction ofSaqsaywaman was initiated by the ninth Inca, Pachacutec and was continued by his son Tupac Yupanqui Inca, between 1431 and 1508. The construction of Saqsaywaman is testament to the stonework engineering ability of its builder architects: Huallpa Rimachi Inca, the first and main Builder, followed by Maricachi Inca, Acahuanca Inca and Calla Cunchuy Inca. The remaining walls lean inward, which according to current theory allowed the Inca to create a more earthquake resistant structure, and are comprised of mortar-less joints so closely interlocked that even a single sheet of paper cannot fit between the blocks.”
The Geologic Puzzle at Saqsaywaman
On the north side of the Saqsaywaman Archeological Park is a strange outcrop. The outcrop is andesite, but it is marked with north-east trending grooves. It is so deeply grooved in fact, that it’s known as “El Rodadero” – the roller coaster.
In a quick scan of the geologic literature, it appears that ideas for groove formation have ranged from glacial grooves, to faulting, and to the andesite being plastic to partially molten as it was extruded and basically corrugated due to the overlying wallrock. The consensus on groove formation appears to be that of the viscous flow model, but here are links to the references I found, so decide for yourself:
This is one of the best visualizations for global temperature change that I’ve seen. It’s created by Ed Hawkins, a climate scientist in the National Centre for Atmospheric Science at the University of Reading. As noted by Ed Hawkins:
“The animated spiral presents global temperature change in a visually appealing and straightforward way. The pace of change is immediately obvious, especially over the past few decades. The relationship between current global temperatures and the internationally discussed target limits are also clear without much complex interpretation needed.” – Ed Hawkins, Climate Lab Book
Lima, Peru is fast becoming a preeminent food hotspot with traditional Peruvian foods and various fusion cuisines that I found extremely delicious. And of course it is also internationally known for extraordinarily magnificent museums such as the Museo Larco with its collection of pre-Columbian art.
Lima, the capital city of Peru, has a population of almost 10 million people that is dispersed among its 43 districts. Known as the “City of Kings”, Lima was founded by the Spanish conqueror Francisco Pizarro in January 1535 when Pizarro confiscated land on the south bank of the Rimac River where the Inca curaca (local ruler), Taulichusco, had his palace. Lima then became the most important city and capital of the Spanish holdings in South America until the mid 1700’s. Lima’s supremacy later diminished as northern South America became a part of the Spanish Empire (known as the Viceroyalty of New Granada and established in 1717) and with the creation in 1777 of the Viceroyalty of La Plata, which encompassed the present-day territories of Argentina, Bolivia, Paraguay.
“The authenticity of the Historic Centre of Lima is intact as it largely preserves the original features of its urban foundation design, as a checkerboard, and the expansion area from the XVI to the XIX century, including old pre-Hispanic paths heading North (Chinchaysuyo) and East (Antisuyo).”
The Plaza de Armas is near the center of the Historic District and thought of as the birthplace of the city. There is no original building remaining adjacent to the plaza, but the bronze fountain in the Plaza’s center was erected in 1650. Some of the more significant buildings now surrounding the Plaza include the Cathedral of Lima, the Government Palace, and the Archbishop’s Palace of Lima.
The construction for the first church on the Cathedral of Lima site was completed in 1538. The present cathedral is the result of many renovations and rebuildings and is largely based on the original plans of the Cathedral that was devastated in 1746.
The Government Palace houses the official residence of Peru’s President and executive branch. The palace’s original construction began in 1535 over the residence of Taulichusco, the then Inca curaca. Similar to the Lima Cathedral, the Government Palace has been extensively rebuilt over the years.
The Archbishop’s Palace is sited on land that Pizarro designated for the head priest of Lima’s residence shortly after the city’s foundation in 1535. The present Archbishop’s Palace was built in 1924 and is well known for its ornate Moorish-style balconies.
Two of the other places that I visited – and I think are well worth going to – in the Historic Centre are the San Francisco Monastery and the Plaza San Martin. The San Francisco Monastery (Convento de San Francisco) is one block northeast from the Plaza de Armas. The Monastery was consecrated in 1673 and completed in 1774, although it has been extensively repeatedly rebuilt. Of note are its famous catacombs where a series of underground burial vaults were used until the mid 1800’s.
The Plaza San Martín is located about 5 blocks southwest of the Plaza de Armas. The Plaza was dedicated on July 27, 1921 to honor the 100th anniversary of Peru’s independence. An equestrian statue of José de San Martín is the Plaza’s central statue.
A video of Lima’s Historic Centre, done by UNESCO/NHK, gives a good overview of this area:
Lima Area Earthquakes – the Forces Behind the Rebuilding of the City
As noted several times in the text above regarding Lima’s Historic Centre, no wholly original buildings exist today, and those that do stand today have usually been repeatedly rebuilt. The continued destruction to Lima’s architecture is due primarily to several strong earthquakes in the Lima region that have occurred periodically.
“Peru is located on the western edge of the South American crustal plate, one of several large lithospheric plates that comprise the Earth’s crust and slowly move with respect to one another. The boundary between the South American plate and the Nazca plate to the west is one of the most seismically active areas of the world. The Nazca plate is being overridden and driven beneath the westward-moving South American plate. This collision between two large segments of the lithosphere is the source of most of Peru’s earthquakes. Offshore, where the two plates meet, the shocks occur at shallow depth. To the east, as the Nazca plate is pushed downward, the earthquakes occur at progressively greater depth – to as much as 600 kilometers near the Peru-Brazil border. … Shallow earthquakes are potentially more destructive than deep shocks of the same magnitude because they generate stronger surface waves.”
Although earthquakes are common in Peru, there have been several significant quakes in the Lima region since its founding. Much of the city was destroyed because of earthquakes in 1586, 1687, and 1746 (Philibosian, 2001) that had magnitudes from 8.6 to 8.7. More recent, large magnitude earthquakes (8.1 to 8.2) in the Lima area occurred in 1940, 1966, 1974 (Dorbath and others, 1990) and also caused substantial building structural damage and loss of life.
And it is not just the ground movement generated by earthquakes that have been devastating for Peru:
“Records indicate that since the late sixteenth century, large earthquakes centered off the Peruvian coast have generated several destructive tsunamis (1586, 1604, 1647, 1687, 1746, 1865, 1868, 1914, 1942, 1960, 1966, 1996). Of those listed, five were particularly destructive. These include the 1586, 1604, 1687 and 1746 tsunamis, as well as the 1868 Arica tsunami.” (USC Tsunami Research Center, 2005)
Probably the most extensive tsunami in the Lima area occurred in association with the 1746 Lima–Callao earthquake (with a moment magnitude recently estimated at 9.0 – Jimenez and others, 2013). Not only did this earthquake cause considerable damage and loss of life in Lima, but the ensuing tsunami basically wiped out the nearby port of Callao:
“On the evening of 28 October 1746, Lima was shaken by a violent earthquake. Out of a population of 50,000, only about 1,000 people died. But at about 11 pm, a tsunami devastated the neighbouring port of Callao, destroying the port itself and sweeping miles inland. In contrast to Lima, only a handful of Callao’s 6,000 inhabitants survived. Lima was then the most important city in South America, and the port of Callao exported gold and silver to Spain. The disaster was unprecedented for the Spanish in the region, and posed a critical economic threat to the colonial power.” (GAR, 2011)
Given the geologic setting of the Lima, Peru area, it’s a reasonable assumption that earthquake activity is and will be a part of life here.
I just returned from travels in Peru, which took me from Lima to Cusco, to the Sacred Valley, and eventually to Machu Picchu. It was a spectacular trip! Adventure Life, a company from Missoula, Montana, did the trip travel logistics for our group of University of Montana Alumni. They did an amazing job, starting with providing two incredible local guides, Ayul and Teddy. And the Peruvian food that I ate during the trip – it was delicious! Our group size was small with 19 people in total, which for me was a plus, rather than traveling with a huge bus-load of people. We covered a lot of ground during our Peruvian travels and this is the first of several blogs on the trip, starting with Miraflores, a truly captivating part of Lima.
Miraflores is well known for its green spaces. We stayed in the heart of Miraflores near Parque Kennedy, which is named after John F. Kennedy because of the aid he gave to Peru during his presidency. Although artisans, food vendors, and a free wifi hotspot are draws to the parque, probably its best known aspect is that it is home to many stray cats. No one apparently knows for sure where the cats came from. Some say that a pregnant cat was abandoned in the park about 25 years ago and that event started the parque’s cat population. In any event, today there are by best estimates, probably somewhere around 80-100 cats living in the parque that are cared for by its visitors.
The Miraflores Malecón is a six-mile expanse of parks atop the cliffs that fringe
the Pacific Ocean. The Malecón is a great place for walking, bike riding, and sea-scape viewing. We spent time walking through a part of the Malecón known as Parque del Amor (Love Park) where Víctor Delfín’s large carving of a couple in a deep embrace is its centerpiece.
The cliffs that abut the Pacific Ocean in the Miraflores area are made up of alluvial fan sediments that comprise the Plio-Pleistocene Lima Conglomerate. This geologic unit contains sediments ranging in size from cobbles to clay that were sourced in the Cordillera east of Lima and eventually deposited by the shifting Rimac and Chillon rivers in the greater Lima area. As noted by Roux, J.P. and others (2000: Sedimentology of the Rimac-Chillon alluvial fan at Lima, Peru, as related to Plio-Pleistocene sea-level changes, glacial cycles and tectonics, Journal of South American Earth Sciences 13, 499 – 510), and summarized by Koster (2008), the
“clasts are mostly granites, diorites, gabbros and Mesozoic to Cenozoic volcanic rocks. The Lima Conglomerate has a thickness of up to 86 m. It is interrupted in parts by lenticular sand and siltstone lenses that likely represent estuarine incursions caused by sea-level variations”.
The larger clasts from the Lima Conglomerate form the beach pavement, making for a very rubbly beach surface.
Huaca Pucllana, a pre-Inca ruins dating from about 400-700 CE, lies in the midst of a Miraflores residential neighborhood. The ruins encompass about 5 hectares and most prominently consist of a 22-meter high pyramid with 7 levels presently identified that was built by the Lima culture.
The pyramid is made of adobe bricks stacked like books on shelves; fill for the structure mainly consists of sand and gravel from the surrounding area. This building technique is thought to minimize damage caused by earthquakes, perhaps lending to the complex’s remarkable preservation.
The pyramid part of the complex was most likely used as a ceremonial sector. Clay huts and structures that probably functioned as administrative buildings surround the pyramid.
The Lima culture abandoned Huaca Pucllana about 700 CE. From about 800 CE until 1000 CE, the Wari culture occupied Huaca Pucllana, using it mainly as a burial site for the nobility. In 2008, archaeologists uncovered the intact remains of three people from the Wari culture– two adults that were wearing masks and a child that appears to have been sacrificed.
A later social group, the Ychsma (inhabiting the site from about 1000-1450 CE), appear to have reused some of the adobe bricks from the ruins to build what look like temporary shelters on-site and to use the site for offerings and as a cemetery. In 2015, archaeologists found four Ychsma culture mummies (three women and one man) at the complex.
To add to the mystique of Huaca Pucllana, is the presence of a very fine restaurant where we dined during our evening in Miraflores. The food is wonderful and it was equally fun to see Huaca Pucllana in lights as we ate.
Dr. James Hansen (Director of Climate Science, Awareness and Solutions Program Earth Institute, Columbia University) and 18 co-authors just published an article – Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2 °C global warming could be dangerous – in the journal AtmosphericChemistry & Physics. Their article is significant because not only does it raise the issues of superstorms and sea level rise that are associated with human forcing of climate change, but their research also suggests that current climate models do not adequately gauge the effects of ice melt runoff from the Antarctic and Greenland ice sheets. The video embeded below is done by Dr. Hansen and his co-authors and is a good abstract of their recent research findings.
Montana Outdoors just published an article on two Forest Legacy projects that I’m very proud to have worked on – the Haskill Basin and Trumbull Creek projects, which are both located near Whitefish, MT. Both are projects where varied interests have come together for a common goal. As well stated by the article’s author, Allen Morris Jones,
That’s the concept behind the Forest Legacy Program, a little-known conservation workhorse administered by the U.S. Forest Service. Forest Legacy was created in 1990 in response to widespread development turning the nation’s privately owned forests into “nonforest uses”—housing estates, golf courses, and other commercial sites. The conversion of timberland hurt logging and sawmill businesses, cut off recreational access, fragmented critical wildlife habitat, and degraded streams with sedimentation and leaching septic systems.
These projects are also a great tribute to a late colleague of mine from the Trust for Public Lands, Alex Diekmann, who passed in early February. Alex’s hard work and perseverance on these projects makes them a success.
Siccar Point, located on the southeast coast of Scotland, is well revered in the geological community. Outcrops at this locale display ‘Hutton’s Unconformity’. This is an angular unconformity where tilted rock units of about 370 million years in age called the Old Red Sandstone (with a basal layer of conglomerate) lie atop nearly vertical strata of greywacke that are approximately 435 million years in age. James Hutton observed these rock juxtapositions while on a boat trip past Siccar Point in 1788 with James Hall and John Playfair. His observations and contemplation of this unconformity formed a basis for his theory of repeated cycles of deposition, uplift, and erosion, which was later known as uniformitarianism.
The British Geological Survey posted a new video on Siccar Point a few days ago. Their video features amazing drone video of the locale and good accompanying audio. It is well worth a view!
Spending time in Puerto Rico is a fantastic experience. The beaches are wonderful, the rain forest of El Yunque National Forest is unique in the U.S. Forest Service’s holdings, the bio-bays are enchanting, and of course there are intriguing rocks that underlie all these natural wonders.
Puerto Rico is the eastern-most island of the Greater Antilles, which is a group of islands in the Caribbean Sea that includes the countries of Cuba, Hispaniola (Haiti and the Dominican Republic), Jamaica, and the U.S. territory – the Commonwealth of Puerto Rico. Puerto Rico (and its outlying islands of Culebra and Vieques), along with the U.S and British Virgin Islands are the subaerial form of a microplate that exists at a seismically active plate boundary between the North American plate and the northeast margin of the Caribbean plate. Because of the tectonically-active location, this area has experienced large magnitude earthquakes and destructive tsunamis.
38 on Puerto Rico’s Geology, Geochemistry, Geophysics, Mineral Occurrences:
The island consists of volcaniclastic and epiclastic rocks of volcanic origin as well as other sedimentary rocks of Late Jurassic to Paleocene and Eocene age and intrusive mafic and felsic plutonic rocks of Late Cretaceous and early Tertiary age. These rocks are overlain unconformably by Oligocene and younger sedimentary rocks and sediments.
Touring Puerto Rico’s North-Northeast Area
I flew into San Juan, but as soon as I picked up a rental car, I headed to the beaches in the Piñones area. This area is about 10 miles east of San Juan, located along Route 187, which skirts Puerto Rico’s north coast, linking San Juan and Loíza. Route 187 is a scenic drive and there are many places to pull off the road and enjoy the beaches. The beaches of Pinoñes fringe a mangrove forest and large sand dunes. The beach areas are further enhanced by eolianites and beachrock creating a relatively continuous barrier that protects the shore and make for a relaxing swim.
Further east along Puerto Rico’s northern coast, the beaches of the Luquillo area provide better access to some surf. La Pared, the Wall, is one of these surf beaches and is located nearest to downtown Luquillo. Its western end is a narrow stretch of sand shaded by palm trees where there is easy access to set up beach chairs and enjoy life. East from here, the surf increases and this is where most surfing action occurs.
The El Yunque National Forest is the only tropical rain forest in the U.S. National Forest system. Although it is one of the smallest of the national forests (approximately 28,000 acres), its biological diversity is immense. The US Forest Service provides an excellent description of El Yunque:
The rugged Luquillo Mountains that rise to 3,533 ft. above sea level comprise most of the forest land. Their steep slopes can sometimes receive rainfall of over 200 inches (508 centimeters) per year at higher elevations. Caressed by gentle easterly winds the forest has an average temperature of 73° F (21° C), and seasonal changes are almost imperceptible. It is the ideal climate for exuberant tropical vegetation. The rain forest is noted for its biodiversity; it is “home” to thousands of native plants including 150 fern species, 240 tree species (88 of these are endemic or rare and 23 are exclusively found in this forest). The El Yunque National Forest has no large wildlife species, but hundreds of smaller animals abound in this gentle forest, many of which exist nowhere else on the planet.
Driving south on Highway 191 from Palmer into El Yunque, there is a progression in forest types as elevation increases. Forest growth changes from Tabonuco (tall trees and low light intensities at ground level), to Palo Colorado (upland swamp of short-statured trees with shallow root systems), to Sierra Palm Forest (overall smaller vegetation of the two previous forest types found on steep slopes, unstable soils and streambeds). There is one
last forest type – the cloud forest (upper edges of the Palo Colorado and Sierra Palm Forest types with water-saturated soils), but to see this, you need to hike. A good hike to get to the cloud forest is to do the climb to the Mt. Britton Tower. The trail takes off from Highway 191, but you have to walk up the road from the last parking area to get to the trail head. It’s a 0.8 mile, one-way hike and climbs 594 feet in this short distance. The trail head is well signed and the trail is paved and maintained.
Highway 191 winds its way through El Yunque National Forest within the Cretaceous Tabonuco Formation. The Tabonuco Formation is marine in origin and contains andesitic
to basaltic volcaniclastic sandstone, mudstone, volcanic breccia, and conglomerate. One of the best places in El Yunque to see the Tabonuco Formation is at La Coca Falls. La Coca Falls is easily accessible and is one of the first spectacular features to be seen along Highway 191 as one travels up into the forest.
About 0.5 miles north of Mt. Britton lies El Yunque, a towering peak that has been iconic in Puerto Rican history since pre-Columbian times. El Yunque (Spanish for anvil) is 3,412 feet high, breaking through the old growth forest where it is covered by clouds. The topographic prominence of El Yunque has recently caught the attention of geologists who wondered why the peak is not covered with vegetation and eroding rapidly given the area’s humid tropical climate. Their research indicates that El Yunque is part of an ancient supervolcano named Hato Puerco that was active about 145-66 million years ago. The hardness and chemical properties of the rocks that form El Yunque and deter rapid erosion came from being cooked in the chamber of the supervolcano.
Puerto Mosquito and the Bio-Bay of Vieques
The island of Vieques lies about 8 miles east of Puerto Rico. Vieques is an island
municipality of Puerto Rico and was home to a major naval base until 2003. Consequently, much of the island escaped intense development. The easiest way to get to Vieques is on the ferry that leaves from the town of Fajardo. The ferry trip is probably usually uneventful, but on the way back from Vieques to Farardo, there was a multiple vehicle smash-up during loading time. Just a couple hour delay, which wasn’t too bad, considering all the damage.
Of particular interest to me was the bio-luminescent bay, Puerto Mosquito, found in the southern part of the island and considered to be the largest and brightest of Puerto Rico’s bio-bays. The luminescence in the bay is caused by a dinoflagellate, Pyrodinium
bahamense, which glows whenever the water is disturbed, leaving a trail of light. A combination of factors results in ideal conditions for the growth of Pyrodinium bahamense and hence thebioluminescent bay. These factors include red mangroves that surround the bay adding vitamin B-rich bacteria to the water, the restricted outlet to the Caribbean, the shallow water depth, water temperature and salinity, and little variation in atmospheric conditions. All this combines to give an amazing light show!
I kayaked Mosquito Bay with one of the local tour companies, JAK Water Sports. My kayak had a clear bottom which really enhanced the streaming of the bio luminescence, I also did the tour during the dark of the moon – another plus for maximum viewing and definetly a bucket-list event.
And of course the beaches of Vieques are excellent. I stayed in Esperanza, on the south side of the island. Even within walking distance, there is no lack of desirable beach. The nearby beach locally known as Coconut Beach
even had rock exposed. The exposed rock is a Cretaceous granodiorite that is, needless to say, extensively weathered.
The Dog Town Mine Tertiary fossil vertebrate locality is nestled on private property within the southern extent of the Elkhorn Mountains, southwestern Montana. The locality is about 20 miles southwest of Townsend, Montana, where Mesozoic and Paleozoic carbonate, quartzite, and red-colored mudstone, siltstone, and sandstone rocks underlie Eocene (Chadronian) strata. These unconformable Eocene strata contain the Dog Town Mine vertebrate fossil locality.
Earl Douglass (yes, that Earl Douglass of the Dinosaur National Monument fame) first collected at the site on Friday, June 27, 1902 (based on transcriptions from Earl Douglass’ journals done by Alan Tabrum and volunteers from the Carnegie Museum of Natural History). According to his journal, Douglass met a man from Toston, Montana, on horseback and this person told him about the Dog Town Mine, which was located on the divide between the Toston/Townsend and North Boulder Valleys. Douglass was headed to the North Boulder Valley anyways, so he rode to the mine where he found invertebrate fossils (brachiopods and bryozoa) in carbonate rock which was in contact with the ore deposit. A Mr. Allen, who he dined with that evening, told him that more fossils could be found a little ways west of the mine. After dinner Douglass rode a short way west of the mine and found banks along a ravine that looked like Tertiary White River beds. Here he found “Oreodont, Ischyromys, Palaeolagus, Titanotherium, and turtle remains” (June 28, 1902, Douglass Journal entry). This area is the present Dog Town Mine vertebrate fossil locality.
Tertiary strata at the Dog Town Mine are fine-grained, predominantly consisting of siltstone with minor fine-grained sandstone units. The deposits are probably of aeolian origin, originating from areal sediments rich in volcanic ash. These deposits are probably similar lithologically and in mode of origin to those Tertiary White River units found at high elevations within the Laramie Range and Medicine Bow Mountains (Evanoff, E., 1990, Early Oligocene paleovalleys in southern and central Wyoming: Evidence of high local relief on the late Eocene unconformity: Geology, v. 18, p. 443–446; Lloyd and Eberle, 2012, A late Eocene (Chadronian) mammalian fauna from the White River Formation in Kings Canyon, northern Colorado: Rocky Mountain Geology, v. 47, no. 2, p. 113–132).
Vertebrate fossils have been collected at the Dog Town Mine site for various museums since Douglass’ initial collection. The Carnegie Museum of Natural History in Pittsburgh, PA houses a collection from the site as well as the Museum of the Rockies in Bozeman, MT.
Most vertebrate paleontologists probably think of the spectacular dinosaur finds near Jensen, Utah, when the name Earl Douglass is mentioned. Douglass’s discovery of a partial Apatosaurus near Jensenin 1909 did spark the beginning of his long career with finding more dinosaur material in what we now know as Dinosaur National Monument. But Douglass began his quest for fossil vertebrates while he was in southwestern Montana – several years before he was summoned by the Carnegie Museum of Natural History’s director William Jacob Holland to find dinosaurs.
From the spring of 1894 to 1896, Douglass taught at a one-room school in the lower Madison Valley of southwestern Montana. The school house was located in the lower Madison Valley, directly west of the area known as the Madison Bluffs. These bluffs contain strata that range in age from probably as old as Eocene through the late Miocene. The strata are continental units that include alluvial fan to fluvial trunk stream deposits.
During his tenure at the lower Madison Valley school, Douglass spent much of his spare time exploring the Madison Bluffs. At the beginning of his teaching contract in 1894, he had very little knowledge of vertebrate paleontology and of the area geology. He initially considered the Madison Bluff beds as Cretaceous in age. But when he found a “tooth very much like a Protohippus” (Earl Douglass journal entry on May 12, 1894), Douglass knew that the beds were younger in age. As time passed, he began to find a significant quantity of fossil vertebrate mammal material within the bluff’s deposits. Consequently, he immersed himself into reading about comparative anatomy so he could readily identify the fossil material. Douglass eventually used his collected fossil material for his 1899 Master’s thesis at the University of Montana – ostensibly the first Master’s degree awarded by the University.
Douglass kept journals of his time in the lower Madison Valley, and often detailed both the area geology as well as his fossil finds. Alan Tabrum and volunteers from the Carnegie Museum of Natural History have transcribed many of his journal entries from southwestern Montana. I’ve included two portions of journal entries to illustrate his finding of a horse jaw from the bluffs (above diagram) and one of Douglass’s drawings of “Big Round Top” (an area in the bluffs near the one-room school house) as compared to that same area today in a photo that I took about a week ago.
It’s not difficult to understand how Earl Douglass became enthralled with the geology and paleontology of the Madison Bluffs. In addition to the fossil vertebrates, the bluffs contain many other fascinating geological features. Towards the central part of the bluffs (immediately south of the Madison Buffalo Jump State Park), calcic paleosol stacks mark the boundary between most likely Eocene and Miocene strata. The calcic paleosol stacks contain at least two generations of soil profiles (typically minus the A and upper part of the B horizons). Rootlets and burrows are commonly associated with these paleosols.
Volcanic tuffs also occur within the bluff’s strata, which is really handy for those of us who like isotopic age control for southwestern Montana Tertiary deposits. The tuffs could potentially help age constrain the paleosol stacks and sedimentation within the so far non-fossil bearing part of the bluffs. And with the help of the New Mexico Geochronology Lab, a group of us are working on just that aspect of Madison Bluff geology.