Current Research

Each year the Yamhill River Pleistocene Project works with land owners, local governments, volunteers and professional scientists to facilitate an annual paleo-archeological or paleontological dig during mid to late summer in our project area. We coordinate and do site preparation, access local resources and participate in the digs. Concurrently, we search for fossil and artifact locations on the Yamhill River drainage basin. The specimens found are documented, collected and preserved for further study.
When the season ends we work to stabilize and preserve specimens, update records and maps of the finds. We produce meter grids of site excavations and assist the professional scientists, when possible, in producing papers on the summer's work, and maintain the specimen collection available to scientific investigators and the general public.
Additionally, we are committed to the public trust, and education is a large focus of our annual events. We are glad to display the fossils and artifacts to the public, and have attended elementary and high school classes as well as public service groups to deliver presentations on our Project and the late Pleistocene. We have conducted tours of our paleo-archeological dig sites, participated in job shadow training at Linfield College, and on occasion facilitated student field trips down the Yamhill Rivers.
We have applied a multidisciplinary approach to our project: by drawing on resources from many scientific backgrounds a more complete picture of the distant past is revealed to us. Among the scientists that have been or are actively involved in our project are paleontologists, paleo-archeologists, geologists and forensic pathologists.
Lisa Ripps and Mark Fitzsimmons excavate mammoth remains at the McMinnville Mammoth Fossil Site. "The study of ancient life". Every single find is exciting, whether it is picked up along the river bank or carefully excavated from a dig site or one that can only be described as the "find of a lifetime." While most of what we have collected has little overall significance, we have been fortunate enough to find some truly awesome specimens. All of the specimens are entered into the fossil logs, described, stabilized and maintained for continued study. The entire collection is promised to the Condon Museum of Natural History at the University of Oregon.
Dr. Alison Stenger, Ph.D. studies projectile points with Alia Moore. Evidence of late Pleistocene/early holocene human activity is indeed quite rare in our area. To date we have not found in situ artifacts. The few artifacts we have found have proven to be quite fascinating, from a variety of styles and cover a huge span of time representing possible Haskett points, Cascade culture and recent holocene. The quest for a true Pleistocene human site has escaped us, so far, but the search continues. Dr. Alison Stenger's Institute for Archeological Studies has taken the lead in our Paleo-Archeological studies.
Mark Fitzsimmons studies stratigraphy of the Gilpin Creek Fossil Site. The geology and geography that fossils are located in give us valuable clues to what the paleo-environment was, and where to look for further finds. The matrix or sedimentation that the specimen was located in, its exact location and relationship to other known specimens are studied and logged. Stratigraphy not only at the level of the specimen, but above and below it is recorded, helping us to understand how the specimen came to be where it is and what processes occurred before and after it was deposited.
Marvin Reken and Mike Full attempt to identify a calcaneous: Mammoth or Mastodon? The study of each specimen found is undertaken to try to identify every species of fauna possible, and we do not hesitate to access expert resources such as the Page Museum at the Rancho La Brea Tar Pits. The frequency of finds may speak to the overall density and dispersal of each population, and in turn give insight to the relationship between species and the overall environment and ecosystem. So, the more successful we are at identifying as many finds as possible, the more complete our understanding.
Mack Reid studies a bone fragment for possible evidence of human modification. The relatively new field of taphonomy, literally the study of everything that has happened to a specimen which results in it being in the condition that we have collected it in, yields exciting glances into the past. Whether examining the predatory tooth marks consistent with a dire wolf, the gnaw marks of some ubiquitous rodent, or the greenstick fracture with retouching and polishing that may indicate human modification; taphonomy can either deepen the mystery or bring a moment of pre-history into exquisite focus.
The North and South Yamhill Rivers form the Yamhill River at McMinnville. It is an older, meandering river system that has cut its way deeply into the fertile soil of the valley floor, revealing a cross section of recent Oregon geologic history stretching back more than 50,000 years. 
The geologic history of the late Pleistocene and early Holocene are revealed in the banks of the river like the pages in a book. A preliminary soil gradient study at the McMinnville Mammoth Site, currently radiocarbon dated at greater than 51,700 years, shows this area to be underlain by a thick deposit of variated blue clay, quite pure in places, silty or sandy in others; indicating a low energy water environment, possibly slow river, pools, ponding or a small shallow lake.
A layer of poorly sorted and poorly concreted gravelstone overlays and cuts into this deposit, and is believed to be river bottom gravel indicating an earlier channel of the Yamhill or Willamette river system. This in turn is overlain by more poorly sorted gravel which gives way to layers of sand and silt (again poorly sorted) believed to indicate further, lower-energy flood events, possibly the result of the Bretz or Missoula floods backing up the Willamette Valley.  The entire area finally gives way to sandy-silty layers indicating possibly annual flood events. At the McMinnville Mammoth and Bison Sites, the entire site is overlain by the remains of a recent bank slump,a modern erosional event which is evidenced as a heavy layer of undifferentaited silt and visual remnants of a large slump block cut from the bank above the site.
The unravelling of the geologic story awaits us developing a resource much more knowledgeable in sedimentation and stratigraphy than we are to help us with the project and intigrating several sites into a comprehensive study.
The late Pleistocene and early Holocene deposits revealed by the river's constant errosional process are rich in glacial erratics.
Glacial erratics, geologic specimens that have been transported to our area by the Bretz flood events, come in all shapes and sizes, from a multi-ton boulder sitting on a hillside between McMinnville and Sheridan to small quartzite pebbles shining on the river bottom.
Erratic Rock State Natural Site lies mid-way between Sheridan and McMinnville off Highway 18.  At thirty eight tons, the boulder is the largest glacial erratic rock in the Willamette Valley. Transported here probably attached to an iceberg during the Bretz (Missoula) Flood events, the rock is argillite and believed to be 600,000 million years old.  It is also the only rock of its type outside of Canada. 
We located and then lost to a massive bank slump a large boulder on the bottom of the South Yamhill River believed to be a glacial erratic; but have recovered fine specimens of granite and schist, gniess, some marble, quartzite and petrified wood.
In terms of Geologic Timeline, the 40,000 years compromising the focus of the project is less than the blink of an eye, yet in that time the vast herds of mega-fauna roaming the North American continent suffered a wave of extinctions. Gone are the mammoth, mastodon, giant ground sloth, species of bison, the horse and the camel and many more. Gone as well are many of the super predators that preyed on them: the short faced bear, American lion, saber toothed cat and dire wolf among others. Paleontologists ask why and look for answers in the Yamhill River basin.
During the same blink of an eye, a new species came to dominate the land: humans. The earliest Americans left few traces of themselves as they populated the new world. Paleo-archeologists struggle to put the puzzle of the peopling of the Americas together, with many of the pieces still missing. The 50,000 years revealed to us along the banks of the Yamhill Rivers offer tantalizing clues. Paleo-archeologists study the projectile points for size, style, workmanship and material to establish approximate age, culture and purpose. Fossil bones are examined for possible taphonomic evidence indicating human modification due to predation, scavenge or use.
The Yamhill River system is composed of the South Yamhill River, North Yamhill River, and Yamhill River. With the associated streams and drainages, the resulting 25 or so miles of the Yamhill River system near McMinnville formed the primary geographic focus of this project, although we have expanded our areas of interest into the greater Willamette Valley Pleistocene and occassionally venture wherever curiosity beckons.
The South Yamhill River flows a very winding northeasterly direction in the vicinity of McMinnville. Traveling downstream to its confluence approximately 20.5 miles of the South Yamhill River has been scouted and assessed for fossils and artifacts. The river changes character greatly in this stretch, starting out shallow with a constant current flow in evidence, the bottom and associated point bars composed of fairly well sorted gravels with some sand in evidence. It then becomes a series of pools of slow current connected by stretches of shallow water, with the bottom and point bars of the shallow parts being composed of poorly sorted gravels with more sand and silt in evidence, along with some blue clay and recent muds; the bottoms of the pools consisting often of blue clay. In the lower stretches, the river becomes wider and slower, with little or no gravel in evidence, and the bottom consisting of clay, often overlain by a thin layer of silt.
Traveling downstream to its confluence, approximately 1.8 miles of the North Yamhill have been scouted and assessed for fossils and artifacts. The North Yamhill River is considerably smaller and shallower than the South Yamhill River, and continuing upstream much farther becomes difficult due to overgrowth and obstacles. The North Yamhill River is shallow, with the bottom and attendant point bars composed mostly of poorly sorted gravels and poorly sorted sands with silt. Near the mouth, the river broadens somewhat and shallows, with the bottom predominately silted in, with a fine silty sand.
From the confluence where the North and South Yamhill Rivers form the Yamhill River, it has been floated all the way to Dayton, near its mouth at the Willamette River. However it has only been scouted and assessed for fossils as far as Lafayette, approximately 2.5 miles of river. Throughout this stretch, the river remains fairly broad, slow moving, and little if any gravel is in evidence. The bottom is characterized by the same blue clay, almost universally overlain with a layer of silty mud, depth varying with the particular river characteristics of the location.
So, the Yamhill River system is geographically broken up into three main areas of interest: the rivers themselves, searching for new sites and washed out fossils; the McMinnville Fossil Sites (Bison and Mammoth, grouped together here because of their geographic proximity) with their well preserved disarticulated mammoth skeleton and associated scattered bones of mega-fauna, rodent, mollusk and flora; and the Gilpin Fossil Site with its highly productive jumbled bone bed containing mammoth, bison and sloth. Each area of interest receives a multidisciplinary approach to its study to help us better understand the complex and diverse ecosystem of our prehistoric past. 
Whether washed out or in situ the most fascinating finds have to be the fossils which turn out to be taxonomically diagnostic.  We are fortunate enough to be able to call upon the expertise and skills of Dr. William Orr, curator of the Condon Museum of Natural History at the University of Oregon in assisting with the identification of fossil fauna.  His mentoring of us over the past many years has been an invaluable asset to our endeavours.
The sedimentary deposits also contain the scattered and shattered remains of victims of flood events as well as the exquisitely preserved and relatively undisturbed remains of local fauna. Two separate locations have yielded mammoth remains that have been radiocarbon dated at 12,800 YBP and greater than 51,700 YBP respectively, making the finds significant not only to the paleontologist, but also the paleo-archeologist.
While some species such as mammoth and mastodon have many bones that are strikingly similar; others such as the giant ground sloth, seem singularly strange and unfamiliar. As a general rule, the teeth are the most taxonomically significant of the bones, and a single tooth can definitively confirm a species.
Our fossil collection confirms, through teeth and taxonomically diagnostic bones, the presence in our area of study six varieties of megafauna: mammoth, mastodon, sloth, bison, horse and camelid.
Columbian Mammoth (Mammuthus columbi) Mammoth fossils are some of the most common we encounter, for two very simple reasons: first, they were apparently fairly common, and second, their large size makes their fossil remains easier to see and harder to destroy. Mammoth are known to have gone through several sets of teeth in their lifetime, and our collection represents several distinct sizes.
The columbian mammoth were grazers, undoubtably herd animals, larger than the more famous woolly mammoth or modern African elephant which is its closest living relative. Adults could stand almost four meters tall and weigh nearly ten metric tons. Tusks on an adult bull could be four and a half meters in length.
Colombian mammoth appeared in North America in the late Pleistocene, and are believed to have become extinct approximately 10,000 to 12,000 years ago, with isolated populations lingering well into the holocene. We have been fortunate enough to have radio-carbon dating done on two of our specimens: the Gilpin Site mammoth gave a radio-carbon date of 12,800 ybp and the McMinnville Site mammoth at in excess of 51,700 ybp.
American Mastodon (Mammut americanum) Taxonomically diagnostic mastodon fossils are much more scarce than mammoth, although many of the largest fossil bone fragments could in fact belong to either. Only one mastodon tooth has been found to date, (probably shed from a juvenile to make room for the next tooth and showing a great deal of use related wear), and a posterior right dentary fragment was found while scuba diving the river.  The Royer Fossil Site has yielded a huge tusk fragment in situ which has tentatively been identified by Dr. Orr as Mastodon.
The American mastodon stood nearly three meters at the shoulder, about the same size as the woolly mammoth. They are generally believed to have become extinct at the end of the last ice age, approximately 10,000 to 12,000 years ago, although recent radio-carbon dating indicates some may have survived a few thousand years into the holocene.
The mastodon was apparently far less common in our area than the mammoth; possibly because as a browser that did not live in herds, it tended to forage in the foothills among the forests, away from the flat grasslands bordering the ancient Yamhill River watershed.
Giant Ground Sloth (Paramylodon harlani) Our sloth tooth and two sloth digits as well as a partial upper palate and a humorus, have all been identified as representing Harlan’s Ground Sloth, Paramylodon harlani. The giant ground sloth evolved in South America and migrated north. Of the several genus of sloth that were found in North America, the Harlan's Ground Sloth is the commonest in our area. It was an enormous beast, and at two meters tall and weighing nearly 4000 kilograms, it neared the size of a small modern day elephant.
The giant ground sloth were another victim of the extinction occurring at the end of the last ice age, generally presumed to have gone extinct in North American some 12,000 years ago.  The humerus of a Harlan's Ground Sloth from our study yielded a radio carbon date of 16,620 years before present. 
The flat grinding teeth of this huge beast indicate a diet of grasses, but probably also included twigs and leaves obtained and held in front paws equipped with giant claws.  With its primitive peg-like teeth with the unique "figure 8" grinding surface, dermal ossicles, overly stout broad and deformed looking leg bones, compressed feet and ankles and huge claws; everything about Harlan's Ground Sloth looks strange and out of place.
Extinct Bison (genus Bison) Along with mammoth and mastodon remains, the bones of extinct bison are the most common fossil specimens we have discovered. Several vertebra, leg bones, and a partial mandible of a bison still containing two teeth of this ancestor of our modern buffalo are in our collection. Shape and length of the horn core are the defining diagnostic indicators of the different species of extinct bison, and lacking a skull, our finds can only be classified as belonging to genus Bison, and the bison femur recovered at the McMinnville Fossil Site was radiocarbon dated at in excess of 51,700 years before present.
Near the end of the Pleistocene, the extinct bison was abundant, probably holding on into the early holocene. Like the mammoth, the bison was a grazer and a herd animal, so their remains are fairly common in our area of study. Larger than our present day bison, some species had a horn spread of over two meters.
Bison fossils have been found in situ at both the Gilpin Fossil Site, and the McMinnville Fossil Sites. Some of these fossils show distinct evidence of predation or scavenging, in the form of gnaw marks consistent with wolf-sized predators.
Ancient horse (genus Equus) The horse originated in North America, evolving into its final form, genus equus, before becoming extinct from the end of the last ice age until reintroduced by the Spanish during the "conquest" of the new world.
The horse has a particularly well studied fossil record, with new species having been designated by the subtle nuances of the dental grinding patterns. We have recovered two complete teeth and a tooth fragment of extinct horse, and lacking the expertise of the experts in the field as well as being unwilling to enter into that debate, will classify them soley as "genus equus". Interestingly, one is classified by the Page Museum as from an ass or onanger.
The small, yet well ossified distal epythesis of a horse cannon bone, as well as the rather long overall length of a shard of a horse tooth, suggest that we had at least vastly different sized adults, if not different species, in our area. Hopefully, new and more complete finds will shed light on this mystery.
Large Headed Llama (Hemiauchenia macrocephala) After going for years after we found it without an identification, the Page Museum at the La Brea Tar Pits was able to identify for us a tooth as belonging to an extinct camelid, Hemiauchenia macrocephala the large headed llama. The small tooth was identified as a fetal tooth showing no wear to indicate the young animal had ever used it. This single tooth is, to date, our only identified fossil camelid.
Camelids (camels and llamas) evolved and diversified in North America. Camels migrated across the Bering Land Bridge to the old world and llamas across the Panamanian Land Bridge to South America. Subsequently, the entire family died out in North America at the end of the last ice age.
Hemiauchenia macrocephala, the large headed llama, is a late Pleistocene llama that stood nearly two meters high at the shoulders. It's skeletal remains show it to be very long and slender, and it was probably a mixed browser and grazer. To date, we know of no other remains of this animal found west of the Cascade Mountains in Oregon. 
(American Indian artifacts are common throughout the Willamette Valley.  The most recent, Kalapuya and related cultures, are evident in a wide distribution of artifacts and settlement sites at surface level or just below as well as an oral history and a rich culture present to this day.  It does not, however, stretch back as far as the late Pleistocene to early Holocene and as such does not constitute the focus of our investigations.)
Cultural Timeline
Alison T. Stenger, Ph.D.
Institute for Archaeological Studies.
Two areas in McMinnville have yielded evidence of ancient people. This evidence is in the form of stone tools, called lithics. Several different styles are represented among the spear points and other stone tools that have been documented, and several different types of stone have been used.
Some types of stone tools have been identified as belonging to specific times and locations.  These are considered "Cultural Phases", or time periods of manufacture. As radiocarbon dating is not useful for non-organic materials such as rock, the shapes and types of tool making scars can often help to date stone implements.
At McMinnville, at least four very old cultural periods have been identified.  These include Haskett and Windust, Cascade Phase, and Frenchman Springs.  A late prehistoric component is also occasionally suggested by side notch and other variants.  The early material (Haskett and Windust) date stylistically to approximately 11,000-9,000 BP (before present). The next style dates to about 8,000-6,000 BP (Cascade Phase). The final very old sequence is about 6,000-4,000 BP (Frenchman Springs).  The more recent material begins about 2500 BP and continues into the late prehistoric period, or a few hundred years ago.
The mineral (lithic) materials selected for use include an agate like material, known as cryptocrystalline silicate, as well as some fine grained basalt and probable dacite. All of the tools are worked on the front and back. Some of the Cascade Phase tools are not serrated, indicating a different use for these spear point looking implements. These may have been used for actions such as slicing.
The above information was generously provided, initially, by Drs. Leland Gilsen, David Rice, Michael Southard.

01  Scouting the Yamhill Rivers
02 The McMinnville Mammoth Site
03 The McMinnville Bison Site
04 The Gilpin Creek Fossil Site
05 The Royer Mastodon Site                    
01 Scouting the Yamhill Rivers   During approximately eight to ten weeks of late summer, the Yamhill Rivers drop to acceptable levels to scout for new sites and search the river banks and bottom for fossils. With patience, a keen eye and a basic understanding of the geology at work in the river system, the persistent explorer can be rewarded with a fossil find from the late Pleistocene. The most common are flood washed shards of bone from two of the largest of the mega-fauna: mammoth and bison; but also in evidence are the fossilized remains of the giant ground sloth, mastodon, horse and camel.
Nearly all of the fossils found while scouting have been washed out of the bank, and down the river. They are found while floating or wading downs the river, walking the banks, or when an area looks promising and has produced repeated finds, snorkeling or SCUBA gear is used to survey the bottom of the river.
While beautiful and identifiable specimens continue to surface, the majority of the bones found are fragmented, show extensive stream wear, and are not taxonomically identifiable. But even the smallest and most inconsequential fragments are plotted on a map and help show dispersion fans that aid in pinpointing more important finds.
Only rarely are in situ remains found and these come in two general categories: those associated with the catastrophic flood deposits which were laid down at the end of the Pleistocene and remains which are relatively untouched by geologic action after initial deposition. In situ flood specimens are generally scattered and usually fragmentary, often showing green bone type fractures and desiccation. They occur in the poorly sorted Missoula Flood deposits which are in evidence in many of the cut banks of the river, and form the scoured river bottom or intrusive dikes in places along the river course. In situ finds which have remained relatively undisturbed by geologic processes since initial deposition of course remain the most exciting but elusive of finds. Preservation of these fossils can be quite exquisite, with the most minute of details clearly visible. Predation and scavenging marks are visible on many, along with green bone breaks, scarring, un-fused epiphyses, and other taphonomic indicators which allow us a rare and detailed look into the conditions of the late Pleistocene and early Holocene of the Yamhill Valley.
River Scouting, the early years  1965 - 2000    Mike Full started grew up on the South Yamhill River rowing his way through boyhood adventures in a small wooden dingey that he bought with money earned mowing lawns.  His first fossil, a mommoth tooth, was not even recognized as a fossil for several years, just an interesting rock.  A small box of bones were the sum total of his curiosity when he went off to college and later became a police officer back in McMinnville.  Curiosity again pulled him to the river and in the summers he found several more bones, carefully logging each one onto a map for future reference.  Soon, Marvin Reken joined him and the "Yamhill River Pleistocene Project" was born.
River Scouting, 2000     Computerization caugtht up with us after finding the McMinnville Mammoth and yearly fossil logs were scheduled to replace the simple "spots on the map", allowing us to study the river in annual cycles.  This gave us a yearly look into where fossils were showing up on the river, allowing us to focus on developing debris fans.  Our first debris fan, "SpearPoint" and second one "Ivory Beach" became study focal points.  
River Scouting, 2001     The summer of ivory!  Numerous pieces of ivory tusk, mostly just shards, littered the beach and river bottom at "Ivory Beach".  Each was charted and logged onto the river maps.  These new finds and previous finds in the area show a developing debris fan that abruptly stops, with no fossil fragments being found in the shallows just upstream.  If our debris fan model proves out, we will be finding a mastodon wearing out of the bank in this area some time in the future.
River Scouting, 2002     Mike Full was posted overseas with the International Police Task Force, USCIVPOL UNMIK and only had one float before leaving.  This yeilded a tusk stub and a bison vertebra.  Nice way to leave!
River Scouting, 2003     Mike Full returned home from his overseas posting in time for only one river float.  It yeilded a bison vertebra, a nice homecoming!
River Scouting, 2004     In the most notable find of the summer, Marvin Reken and Christine Hamilton picked up a tooth root of a large mastodon tooth from SpearPoint beach.  It was quite a mystery bone for several years, until we sent it to the Page Museum for identification.  Mike Full and Dean Gill found the distal end of a large mammoth femur on the gravel river bottom, an impressive looking piece of fossil!  Mike went on to find part of a bison mandble with two teeth still in it, and later a large chunk of ivory from the core of a tusk.  Not a bad year! 
River Scouting, 2005     Small bone and ivory fragments catagorized a year when we did not get the time to spend on the river.  Few floats were made.  Our most diagnostic find was a really nice bison phlange picked up off of the gravel bar at ivory beach.
River Scouting, 2006     The most notable finds of the summer consisted of a juvenile mammoth tooth found by Mike adjacent to a small creek drainage that has yielded several other fossils.  We are working to develop a debris fan chart for the area and try to find where the fossils are wearing out from.
Mike also picked up a ten inch long peice of a small mastodon tusk round near where a small mastodon tooth was picked up many years before.  We are working on developing another debris fan to determine where these fossils are coming from. 
River Scouting, 2007     Oregon Field Guide sent a crew to accompany us on a scuba dive of the South Yamhill river and Mike Full found a huge sloth digit to a Paramylodon harlonii in the channel right off of Ivory Beach!
Mike also found a small humerus while scuba diving off of the McMinnville Bison Site that we could not identify.  Thanks to Dr. Alison Stenger's resources, we got it identitfied by the Page Museum at the La Brea Tar Pits as a humerus to a bighorn sheep.  First fossil of one we have heard of west of the Cascades.
A mammoth tooth and a bison vertebra rounded out a fun summer!
River Scouting, 2008     Variety was the key work for 2008.  Scouting the river revealed bison vertebra, part of a bison mandible, a horse tooth, and various ivory and bone shards.
Dr. Lyle Hubbard found a section of tusk from a mastodon, his first ever ivory he is a mastodon hunter! 
While scuba diving, Marvin Reken and Lisa Ripps located a mammoth or mastodon pelvis....what a find!
River Scouting, 2009     The cub scouts had a wonderful outing and found two pieces of mega fauna bone on the banks of "ivory beach".  Several bone fragments were picked up from along the river course during the summer; the most facinating being a bone fragment picked up by Alia Moore has recently been tentatively identified as part of a bison horn core, most probably from Bison antiquus.  A couple of mammoth tooth plates and two bison molars rounded out a good summer of fossil hunting.
River Scouting, 2010     Notable finds included mammoth tooth plates; one discovered by Joanie Livermore near the Royer mastodon site and another by Mike.  Two bison molars were picked up off of the gravel river bottom as well scattered pieces of tusk ivory and the distal end of a bison femur.  On "Ivory Beach" a beaver femur was found by a Educational Recreational Adventures crew member who was working on site preparation. 
River Scouting, 2011     Notable finds include a rib from the McMinnville Mammoth discovered by Mike Full and Marvin Reken, proturding from the bank of the South Yamhill River at the downstream edge of the McMinnivlle Mammoth Site.  It had been visible for several years, with just te proximal end of the large nearly intact rib barely protruding from the bank, resembling a cobble.  Only careful examination revealed what it was to us. 
Later in the summer, Mike checked a developing debris fan and found a section of the back of a mastodon skull with part of the foramen magnum visible, protruding from a gravel bar on the bottom of the river.
Rounding out the summer were several shards of ivory, two cervid teeth and a couple of mammoth tooth plates....a good year!
River Scouting, 2012    A year of firsts!  Marvin Reken spotted the proximal end of a mammoth tibia/fibula protruding from the gravel over the fossil layer approximately 120 feet downstream from the registration point of the McMinnville Mammoth Site.  It represents the first articulated mega fauna bones we have found if it is not actually fused.  (Final preparation and preservation will show us whether or not it is fused or two articulated bones).  The fossil is possibly from a different mammoth, not the McMinnville Mammoth, but still a great find!
Marvin Reken and Mike Full found a sloth claw, only our second ever, on a river scout which included finding fifteen fossils in a single dive and developing a new debris fan exactly where we expected to find one, further validating our theory of being able to locate eroding fossils by their debris fans.
SCUBA diving, Mike Full and Joanie Livermore found a beautiful bison horn corefrom a Bison antiquus.  Examining it lead to the identification of another fossil, found years before, as a bison horn core, possibly from Bison latifrons.  If so, it will be the first Bison latifrons documented in Oregon.  We will be travelling to the Idaho Museum of Natural History at Pocatello this fall to get the answer!  It comes from a debris fan where several other bison bones have surfaced.
On the same trip, we found an exquisite baby mammoth tooth, only 3.75 inches long.  It is in absoultely perfect condition and represents the first true infant tooth from a mammoth that we know of in Oregon, and sheds light on the Yamhill Valley population of mammoths, suggesting they were a resident population, not "just passing through".
Students from the McMInnville High School located a concreted fossil that had weathered out of the McMinnville Mammoth Site, about two hundred meters downstream from the site.  It turned out to be two phylanges to the McMinnville Mammoth, still articulated.  First unequivocal pieces of the McMinnville Mammoth found articulated.
Not to be outdone, members of the North American Research Group working the McMinnville Site, took time to cool off on ivory beach and Rose found yet another baby mammoth tooth.  Nearly a perfect match to the first one, they represent the upper right and left molars.  We are naming the baby mammoth represented by this tooth "Little Rose".
Marvin Reken and Mike Full, on separate river floats, each found another mammoth tooth, bringing the total for the summer to FOUR mammoth teeth in a single year, our best yet.  During Mike's float, he also found a fused bison tibia/fibula.
SCUBA diving off of the McMinnville Mammoth Site, Marvin Reken found a rib to the McMinnville Mammoth and Mike Full found a piece of a mammoth scapula, not from the McMinnville Mammoth.
On the final float of the season, Mike Full (YRPP) and Richard Kimbell (NARG) found a nice cervid tooth and the proximal end of a scapula from a Harlan's Ground Sloth Paramylodon harlonii.
02 McMinnville Mammoth Site  (Refer to scientific papers located in the "Publications" section of the web site for stratigraphic studies, fossil identifications, taxonomic descriptions, and other information of general scientific interest on this site. Research at this site is ongoing, and it is closed to the public without specific reason and permission from the City of McMinnville which controlls access to the site.)
Discovered in 1991 by Mike Full, the McMinnville Mammoth Site contains the disarticulated remains of a small adult, probably female Columbian mammoth, (Mammuthus columbi). The remains were located on a section of the South Yamhill River undergoing active errosional processes. The intact left tusk laying in the water at the foot of a vertical cut bank, and five more fossilized bones were observed protruding from the bank, to include both scapulas, two ribs and a left tusk socket.
The find was immediately reported to Dr. William Orr, curator of the Condon Museum at the University of Oregon and Dr. Orr sent Roberty Linder to assess the site and confirm ancient fossil elephant remains.
1991 - 1997 Summer Digs.....First efforts and a huge learning curve     Due to the ongoing erosional process and the danger of losing the fossils to floods or bank slump, a hasty dig was initiated immediately to extract visible fossils and assess the extent of the remains. Registration points were established, and a meter grid pattern initiated to plot all fossil remains recovered. Initial indications were that a substantial portion of the fossils remains might still be in-situ at the location.
These initial excavations were carried out by Mike Full along with local friends, family and volunteers. Fossils extracted were restored and preserved by Mike Full with input from various sources, including the Smithsonian Institute in Washington D.C. An agreement was made with Dr. Orr that the fossils would remain in the care of Mike Full, but that the entire fossil collection and records would be public domain, and that the Condon Museum could request ownership at any time (an agreement that continues to this day).
1998 Summer Dig.....The first professional dig     Dr. Robsen Bonnicshen, director of the Center for the Study of the First Americans, then located at Oregon State University was contacted and assessed the site for a possible excavation. His team of paleo-archeologists conducted a dig, along with a taxonomic and taphonomic alalysis of the fossils already extracted from the site. Dr. Bonnischen facilitated a radiocarbon dating test of a fragment of the mammoth maxillary bone. Stafford laboratories, Boulder, Colorado conducted collagen dating. The bone was in excellent condition and yielded an XAD-Gelatin date with a 14C Age of >46,400 RCYBP.
Additionally, Dr. Bonnicshen and his team conducted a stratigraphic survey of the site. His findings are explained in detail in the published paper mentioned above. The fossil material is located in a sandy blue clay matrix, overlain by a poorly sorted gravel flood deposit. This in turn is overlain by several meters of sandy-silt flood deposits showing obvious sedimentary layering. The sandy blue clay layer extends down below the water line, to an undetermined depth. It bears not only the fossil remains of the Columbian mammoth, but also scattered remains of bison, at least one other mammoth, rodent and rabbit as well as fresh water mussel and snail fossils. Also in evidence is flora consisting mainly of twigs and small bits of wood, with an occassional limb or small trunk of a tree.
2007 Summer Dig.....Overland access enables the site to be worked vertically, top to bottom      During the summer of 2007, Dr. Alison Stenger and her crew from the Institute for Archeological Studies conducted a summer dig on the McMinnville Mammoth Site. While scouting the bottom of the river for fossil bones that had possibly erroded from the mammoth site, a bison femur was found protruding from the bank not far upstream from the McMinniville Mammoth Site. Registration marks and the meter grid system was continued, and the summer dig was expanded to include both the mammoth and bison sites.
The premier find at the Mammoth Site was made by Mark Fitzsimmons of Alison Stenger's staff: the upper pallet of the mammoth, complete with one molar. This find could be fit with the molar originally found into place, and the left tusk socket found on the first year's dig also fits perfectly into place. With a small skull plate found years earlier identified as a right orbital, and the right zygomatic arch also found by Mark the same year, it is possible to imagine the skull taking shape before your eyes!
To date, approximately a quarter to a third of the mammoth skeleton has been recovered, consisting of skull parts, three of four molars, the aforementioned left tusk, several ribs and vertebra, both scapula and a femur. The material is in very fine shape, showing little evidence of errosional wear or dessication and exfoliation. Green bone breaks are common (possibly trampling fractures) as well as gnaw marks from predation and/or scavenging. The gnaw marks are consistent with dire wolf and rodent. Photographs in-situ were taken of specimens recovered at both sites along with GPS coordinates and a paper was produced for the City of McMinnville detailing both finds. This paper is also included in the publications section mentioned above.
Curiously, while many of the smaller bones, such as vertebra, and hundreds of bone fragments have been located, which indicates this is a carcass that was predated and/or scavanged where it died and not subjected to high velocity aquatic dispersal, land slump or other high energy natural occurrance; the heavy and dense upper and lower leg bones have not been fount in-situ. The sole leg bone found, a femur, was fifty yards downstream found worn out of the bank, and can not be conclusively demonstrated to be from this mammoth.
2009 Summer Dig.....Site expansion and careful scientific methodology    The 2009 Summer Dig began 08 August, and continued through 23 August.  It was conducted by the Institute for Archeological Studies, Instructed by Dr. Alison T. Stenger and Dr. Lyle Hubbard; oversite by Dr. William Orr.  The class, conducted through Chemeketa Community College,introduced students to field archeological and paleontological methodology, with an emphasis on practical field work.
The same grid was used as on previously established digs, and with some phenomenal assistance from the local gang, the City of McMinnville, and especially from Waldo Farnham who donated the use of his track hoe and operated it himself; we expanded the available area of the dig by about 300 percent.
Dr. Alison Stenger and Dr. Lyle Hubbard conducted classroom instruction and the crew from the Institute for Archaeological Studies acted as staff and instructors on-site.  Dr. Stenger produced the site paper, which is available under "publications" in the User section of the website.
The students had an extremely successful class, and we soon had a bison vertebra emerging from the gravel Bretz flood layer just over the fossil bearing blue clay layer of the site.  Once into the site, the right tusk socket of the Columbian Mammoth began to emerge, complete with the right tusk in it.
The right tusk had been broken, during the animal's life, undoubtedly through normal use and wear, and had been worn down smooth at the stump end through continued use.  Another amazing indication of the story that each fossil has to tell!
2012 Summer Digs......Tracks in Time, Possible Pleistocene Mega Fauna Track Discovery  The 2012 digs were hampered by unit availability.  Much higher than normal early rainfall levels and record summer month river flows made the site inaccessible in 2010 and 2011.  In 2012, again due to unusually high water levels, the site was not accessible until late July.  Additionally, the South Yamhill River is a very active system and the site was found to be covered with slump and depositional overburden.  Equipment brought in to clear off the site became mired and it was impossible to clear off the entire dig site.  <?xml:namespace prefix = o />
Clearing off the site to the limits of the available equipment and by hand resulted in two ends to the dig being opened up, with a substantial amount of slump material left in between, effectively dividing the dig into two different areas. Still, on one end of the dig, an area large enough to view as a whole was excavated to a single level for the first time and the results were startling: 
Tracks Discovered!     McMinnville High School students participating in a fieldtrip with instructor Cory Eklund and Yamhill River Pleistocene Project volunteer on-site scientist Dr. Lyle Hubbard excavated several contiguous square meter grids.  At the end of the second day, the students (now hot and tired) tended to excavate differentially, scooping out softer material and avoiding hardpan.  This left a series of “potholes” in the otherwise flat excavation surface.  What we had been passing off as random variations in the strata now showed what appears to be uniform size and recognizable patterning, resembling an animal track way.  The tracks appeared in size and shape consistent with what one would expect to see in mammoths. 
The following weekend, the North American Research Group conducted a scheduled dig at the site and members were briefed as a matter of interest to look for more evidence of the track way as they excavated.  More tracks were discovered, these were a bit more carefully developed, out of curiosity.  At the conclusion of this dig and after a bit of internet research, the possible tracks were identified as most probably belonging to mammoth.  Again, mostly as a matter of curiosity, they were mentioned to the next two groups scheduled to dig the site: a Linfield College class under instructor John Syring and the Institute for Archaeological Studies under Dr. Alison Stenger, also the volunteer on-site scientist for the Yamhill River Pleistocene Project.
Tracks Identified!     Dr. Stenger who showed great interest in the possibility of the site containing mega fauna tracks, began developing resources and researching the possibilities.  As the scientist in over site, Dr. William Orr was also briefed on the possibility of Pleistocene tracks.  Dr. Lyle Hubbard, who had kindly volunteered to act as on-site scientist for the Yamhill River Pleistocene Project also committed to being a resource in the developing investigation.
During the scheduled digs, Dr. Stenger’s group concentrated on developing the suspected animal track way while the Linfield College students excavated adjacent grids down to the fossil bearing layer.  These were the last scheduled digs of the summer and scheduled to last only two days. 
Dr. Stenger started by adding small amounts of water to each suspected track depression, darkening them to contrast with surrounding matrix.  Examinations of the “tracks” showed size, shape and patterning which matches modern elephant track ways and known, confirmed mammoth track ways.  The depressions were photographed and a site diagram was started.
At the end of the second day, suspected prints from the previous digs had been cleaned off and dressed for photographing, measurements, sketching and prepared for further development the next weekend when Dr. Hubbard had organized an additional crew consisting of Oregon Museum of Science and Industry volunteers with excavation and casting experience to finalize the preparation of the suspected tracks and produce casts.
The possible mammoth track way coincides with past observations of “soft spots” found while excavating adjacent grids and during the original horizontal digs inside the densest part of the excavated bone bed to date.  These possible tracks were not recognized for what they might be and therefore not documented.  
Tracks Lost!     The OMSI crew arrived to find that the carefully excavated grid squares had become inundated with ground water during the previous week due to the trench channeling ground water away from the grids having failed.  The grids were approximately six to eight inches below the water table and thus formed pools which acted to re-hydrate the fossil and track bearing layer which was now unprotected by the over layer of impermeable gravel stone.
The result was to turn the carefully developed top layer of strata, which had once shown suspected mammoth tracks, some showing what appeared to be faint toe detail surrounded by clearly visible pressure ridges, into unrecognizable goo.  While the affected area only extended approximately two centimeters into the sediment, it was enough to distort or destroy all of the previous work in developing the fragile tracks and the faint pressure ridges surrounding them.  Salvaging useful information would mean carefully cleaning the surface of the dig and excavating what remained of the tracks for depth and bottom details.  
Re-Developing the Tracks     Work was started immediately to see what could be salvaged from the mess in the two days available for the dig.
Re-developing the tracks consisted of draining the grids and removing material which had flowed into the grids with the water, as well as any remaining overburden of poorly cemented gravel stone ancient riverbed deposit to get to the fossil bearing layer, then carefully working down through the layer of “goo” to expose the differentiations that indicated tracks.  The tracks, as expected, are in the fossil bearing layer which tended to consist of sandy silty clay, very compacted and hard to excavate.  The suspected tracks appear to be depressions in the surrounding matrix that are filled with a much more uniformly sorted sandy clay that is poorly cemented and more easily excavated, or in some cases filled with silty blue clay, also more easily excavated than the fossil bearing layer.
Careful observation as the excavation progressed appears to show not just the suspected mammoth tracks, but bison, ground sloth and deer as well.  The sandy clay still did not hold crisp detail well, side slump and fill in were apparent in nearly every track and many tracks appeared to have been stepped on or in, partially destroying them or rendering them quite equivocal when viewed singularly.  When viewed as a whole, some directional tracks are discernible in the limited area exposed, adding credibility to the scenario that we are looking at a late Pleistocene river bank where mega fauna came to water alongside the bones of a Columbian mammoth.
03 McMinnville Bison Site 
(Refer to scientific papers located in the "Publications" section of the web site for stratigraphic studies, fossil identifications, taxonomic descriptions, and other information of general scientific interest on this site. Research at this site is ongoing, and it is closed to the public without specific reason and permission from the City of McMinnville which controlls access to the site.)
The McMinnville Bison Site was discovered "officially" in 2007, when Mike Full discovered a bison femur sticking out of the eroded bank of sandy blue clay while scouting for the upcoming dig at the Mammoth Site. Its site designation was bestowed by Dr. Alison Stneger of the Institute for Archeological Studies, and it was included in that year's summer excavation. 
We had been locating fossils at this location, just upstream from the McMinnville Mammoth Site and in geologically the same type of strata, for years; protruding out of the same sandy blue clay, overlain with the gravel flood deposit. Mostly, these bones have shown pronounced dessication, some exfoliation and wear, being not in as good of condition as those of the mammoth. The bison femur was in the same great shape as the mammoth bones, showing gnaw marks on both ends, consistent with a dire wolf. 
Previously, the area has yeilded freshwater mussel shells, bone fragments, a mammoth and a bison calcaneous, rib fragments from a deer or elk sized animal, and a muskrat nest containing two exquisitely preserved perfectly articulated muskrats, and a small rabbit skull. 
2007 Summer Dig: The 2007 dig at the bison site was a modest one, only a few square meters. The partially expoused femur was excavated first.  It showed gnaw marks on the femural head, consistent with a wolf sized predator; and the distal epithesis was missing, apparently due to carnivour gnawing.  A cervical vertebra from a bison was uncovered and a few bone fragments, and the site will hopefully yield more in the future.
04 The Gilpin Creek Fossil Site 
(Refer to scientific papers located in the "Publications" section of the web site for stratigraphic studies, fossil identifications, taxonomic descriptions and other information of general scientific interest on this site.  The Gilpin Fossil Site is entirely on private property and is not open to the public.) 
In 2007 Charlie and Max Gilpin, along with their friend Aspen, were playing in the Creek that runs through their property and enters the South Yamhill River just downstream. Their attention was drawn to a strange looking object weathering out of the bank: it turned out to be a large molar from a mammoth. John Gilpin (Charlie and Max's father) contacted Dr. William Orr of the Condon Museum at the University of Oregon who confirmed the discovery, and notified Mike Full. A site assessment turned up several more bones, including part of a large mammoth scapula, in the log and vegitation clogged stream course. 
The Gilpins had a trip to Los Angelos to appear with their fossils on the Tonight Show with Jay Leno. Upon returning, they embarked on a backyard adventure that netted dozens of late Pleistocene fossil bones. Participating with Dr. Stenger, John Gilpin had a peice of mammoth bone radio-carbon dated. The dating came back at 12,800 YBP, making it a very exciting find from the perspective of paleo-archeology. Early human habitation is known to have occurred by then. 
With the help of Dr. Orr, and later that of Dr. Alison Stenger and her contacts and resources, several of the bones were found to be diagnostic. In evidence so far are mammoth (Mammuthus columbi), Harlan's ground sloth (Paramylodon harlonii), extinct bison and beaver. Closer taxonomic study will undoubtably confirm further species. John Gilpin is a staunch advocate for the environmentally friendly excavation and study of the fossil site, and has been wonderfully active and helpful in facilitating the scientists.
2008 Summer Dig: With the high density of finds in Gilpin Creek, Dr. Stenger and the crew from the Institute for Archeological Studies conducted the summer 2008 dig at the Gilpin Creek Fossil Site with the permission and amazing cooperation and assistance of John Gilpin. John did a great deal of site preparation, and brought in equipment to establish a road bed down to the site. He and his family furnished a parking area, water, sanitary facilities, and a great deal of participation, support and friendly conversation throughout the summer.
Of great interest was a red jasper Cascade style projectile point found in the stream bed at the fossil site by Mike Full. This was followed up by the even more exciting finds by the Gilpins, locating two Haskett style projectile points in the same location. While no human component has been demonstrated in situ yet, the discovery of the ancient projectile points in close proximity to a fossil bed is indeed exciting. 
The summer, 2008 dig was laid out on a meter grid with registration points. The stream bed was thouroughly searched, and the area next to it carefully excavated. Many bone fragments were found in situ, and much further study is needed to determine whether they were initially deposited here, or were washed downstream from some unknown location. 
The fossils are undergoing preservation and restoration by Mike Full, and John Gilpin is maintaining care and custody of them, although he has pledged the fossils, ultimately, to the Condon Museum. The grid charted locations on the preserved specimens will be forwarded to Alison Stenger for study and documentation.
05 The Royer Mastodon Site
(The location of the Royer Mastodon Site is given on the maps located in the "User Pages".  It is located on private property and is not open to the public without permission.)
Melissa Royer Riches presented us with a fossil find from her childhood in 2001 which she had collected along the banks of the South Yamhill River.  She related to us that:
"This tusk, believed to be from a woolly mammoth or elephant, was found b Hillsboro resident, Melissa Royer Riches, and a friend, Paul, in June of 1977 on the banks of the north (sic) Yamhill River, a tributary of the Willamette River, near McMinnville.  The teen-agers first thought they had tripped over a root, but excavated and were delighted to discover that they had found a fossil.  Several years earlier a neighbor had discovered a tooth along these banks.  Later in the rainy season of 1979, approximately February, the renter on the Royer property reported having seen vary large bones along the river, but that they had washed downstream by the time he could investigate." 
Melissa was kind enough to take us to the site, which is actually on the South Yamhill River, and pointed out where she remembered the tusk to have been discovered.  There has been significant bank movement in the intervening years and a large slump now covers the location.  No further in-situ fossils have been recovered from the location.
Sadly, we do not know the name of the neighbor nor where the tooth now resides that was found earlier, since if it could be associated with the tusk, would identify the animal as either mastodon or mammoth.  It is listed here as a mastodon as it was tentatively identified as such by Dr. William Orr of the Condon Museum based on general dimensions, proportions and shape.
Also lost is the name of the renter mentioned in Melissa's narrative, who may have been able to provide a more detailed description of what he saw on the banks of the South Yamhill River.
Each year the site is re-evaluated via a river float and search, sometimes encompassing scuba.  A mammoth tooth plate and a partial scapula to a Harlan's ground sloth have been located downstream on gravel bars, but to date no diagnostically identifiable mastodon material has been found.
06 The Crimmins Mammoth Site 
(This site at present is reported but not researched.  The site location is available only to vetted researchers and the location is given on the maps in the "User Pages" .  The Crimmins Mammoth is on private property .  It is closed to the public without permission from the land owner who controls access to the site.)
The Crimimins Mammoth was discovered by Duane Crimmins in the mid to late 1960's when, as a teen ager, he discovered a mammoth tusk on the family farm.  He realized the importance of what he had found eroding from a blue clay matrix along the North Yamhill River and carefully excavated the badly worn tusk.  Subsequent visits to the site yielded a partial mammoth molar and fragments of a mammoth tooth which he reported to his McMinnville High School teacher.  He has maintained the tusk in a framed shadow box .  Both the tusk and the molar that accompanies it are in remarkably stable condition for a non-preserved/restored/stabilized specimen from the type of strata described.  
The specimen appears to represent the distal portion of a tusk of unknown original length, but probably not much longer than that collected.  It is approximately 1/4 of the tusk in radius, being approximately a four inch arc at its terminus.  The tusk is in excess of three feet long tapering to a  rather fine point.  A tooth plate accompanies the tusk in the shadow box and is consistent with the tusk in condition and permineralization. 
Found separate from the tusk and mammoth tooth plate was a mammoth tooth.  It is nearly complete, representing perhaps 75 to 80 percent of the original tooth and most probably is a left lower molar.  Condition and permineralization are notably different than the tusk and tooth plate and the tooth plate spacing and size are different from the tooth plate found with the tusk, indicating that this find probably represents a different animal.  
The Crimmins Mammoth Site has been covered by a large bank slump, so although the exact location of it is know, it is not at present accessible to excavation or study. 
Cub Scout Den PresentationThe Yamhill River Pleistocene Project makes a continuing effort to reach out to the community in the fields of education and public awareness. We try to communicate this by way of education in the classroom, presentations to groups and organizations and conducting field trips to dig sites or down the Yamhill Rivers. 
Classroom presentations allow children a "hands on" experiance with Pleistocene fossils and hopefully spark a future interest in science. We do our best to field requests from both public and private schools, gear our classes to the age group of the students, and leave plenty of time for questions and answers. We have worked with ages ranging from elementary school through college level. 
Presentations are not limited to schools, as we have also appeared before service groups, research organizations and retirement centers. Again, we tailor our presentation to the interest area of the group and time available. These presentations not only allow us the enjoyment of sharing our adventure with others, but also gives us the opportunity to contact possible resources, help others in identifying their fossil or artifact and at times meet people who have new information for us on fossil or artifact sites. 
On special occassions, we have been able to facilitate educators or students with a field trip to one of our dig sites or even a day on the river searching for fossils. Our first outing on the river with educators on board resulted in finding a small mammoth tusk embedded in a sedimentary deposit, making the memory of a lifetime for an elementary school teacher!
We have hosted classes or projects from Portland Community College, Chemeketa Community College and Linfield College at the McMinnville Site and Gilpin Site, where students excavated the site using current paleontological and paleo-archeological protocols, discovering the remains of mammoth and bison.
A trip up the South Yamhill River provided a den of Cub Scouts the opportunity to spend a day with their fathers, exploring the outdoors, watching wildlife, wading, splashing and swimming in the river, eating "military rations" for lunch, and oh yes, finding a few fossils along the way! 
Inquiries for a classroom presentation, presentation to your organization or a field trip may be addressed to us through the "Contact Us" button on the main menu.