2017 ENC Expedition: The Final Chapter

By Charles Koenig

Five years ago this past January, Steve and his graduate students Dan Rodriguez and Matt Basham launched the ASWT investigations within Eagle Nest Canyon. At the time Steve was helping Dan and Matt plan their thesis research, and Steve and Carolyn Boyd were just beginning to discuss having a joint dirt and rock art archaeological field school. Looking back it is hard to conceptualize, but that short 10-day trip in January 2013 launched arguably the most locally-intensive archaeological study ever conducted within the Lower Pecos Canyonlands.

Since 2013, ASWT has carried out signficant excavations at Skiles Shelter, Kelley Cave, Horse Trail Shelter, Eagle Cave,  and Sayles Adobe, as well as smaller scale testing at 41VV890 and Lonestar Bridge. Each one of these sites has yielded an incredible amount of archaeological data, and we are slowly beginning the long process of analysis and publication. We have wrapped up our work at all but Eagle Cave and Sayles Adobe and this season (2017) marks the final chapter of ASWT field work in Eagle Nest Canyon. (Not really, ASWT will be helping Texas State’s newest archaeology professor, Dr. David Kilby, get to a running start in Bonfire Shelter this summer…but that is for another blog post.)

Backfill or Bust

When we were planning for the ENC work, we established three overarching and ambitious research goals that we would strive to meet over the span of our research. These goals are: 1) understand the natural and cultural history of the canyon; 2) share what we learn with the professional archaeological community and the general public; and 3) preserve the sites and archaeological records for future generations. We are well on our way to accomplishing point one, and as field work wraps up we will continue to learn more about the natural and cultural history of the canyon. For point two, over the past five years we have given dozens of talks at local and regional archaeological meetings; we keep our work (mostly) current on social media; and we already have several theses and publications written about ENC with more on the way. The third point is in some ways the most difficult to achieve, and is one we are spending most of our time pursuing during the 2017 field season.

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A crew member dumps excavated sediment back into a unit in Skiles Shelter.

In order to preserve the sites for future generations, after excavations are complete we stabilize and backfill our units. Backfilling prevents damage that would occur from natural forces (erosion, plants, and animals) and visitors to the sites. At most of the sites our backfilling task is made “easier” by virtue of simply putting the stockpiled fill (i.e., backdirt) we excavated and screened back into the holes. At Sayles Adobe, for instance, once Tori finishes her final sampling in a few weeks we can easily move the piles of screened dirt back into the open excavation units. However, unlike the rest of  the sites, there is no “easy” backfilling at Eagle Cave.

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Steve Black cleans up wall-fall at Sayles Adobe. The massive pile of sediment in the background is the excavated sediment Tori will be able to use to backfill Sayles Adobe.

As we have discussed in several other blog posts, the main trench in Eagle Cave was not backfilled by the Witte Museum in the 1930’s or by the University of Texas in the 1960’s. Since the 1960’s, the once vertical profiles within Eagle Cave slumped and collapsed into a massive depression (see Where Context is Crucial), destroying all intact deposits immediately surrounding the trench. Further, both the Witte and UT archaeologists screened their excavated dirt out near the dripline, and now nearly all of the sediment they removed has been lost down the talus slope. In other words, past Eagle Cave archaeologists left us a massive hole in the center of Eagle Cave without the backdirt to fill it back in.

Witte to UT to 2003

The trench as excavated by the Witte Museum (left) was about 6 feet wide. When the University of Texas Amistad Salvage Project cleaned out the trench in 1963 (center) it was somewhat wider. Fifty years later the once vertical excavation walls had collapsed into a massive depression (right, circa 2003). Yellow arrows point to a unique spall.

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The Eagle trench towards the end of ASWT work (Fall 2016). The same spall is visible on the rear wall  that is pointed out in the above Witte and UT photographs.

Reinforcements Arrive: Eagle Cave Restoration Archaeologists

Prior to the start of the 2017 field season, we were fortunate to apply for and receive a Texas Preservation Trust Fund Grant from the Texas Historical Commission. We applied for this grant as a way to help fund the backfilling efforts at Eagle Cave. As a part of the grant, we had to calculate how much fill was missing from the main trench prior to the start of ASWT excavations in 2014. Based on our calculations, we estimated nearly 225 cubic yards of fill needed to be imported into the site just to re-fill the old Witte-UT trench. 225 cubic yards is nearly 20 dump trucks! This 225 cubic yards is in addition to our own excavated fill from Eagle that we needed to put back. We knew we had to move a lot of dirt, and we knew we needed help.

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Amanda Castañeda

We were fortunate to once again be jointed by ASWT veteran Amanda Castañeda. Amanda completed her Master’s thesis research on bedrock features in the Lower Pecos (see Mortar She Wrote), and was with us for the entire 2016 field season. We also posted job opportunities for two “Restoration Archaeologists,” whose main duty would be helping to move 225 cubic yards of fill into Eagle Cave. We are very pleased to be joined in the field this spring by Juan “Kiko” Morlock and Michelle Poteet.

Kiko Morlock

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Juan “Kiko” Morlock

Hey there! Juan Diego Morlock here, but y’all can call me Kiko! I spent my childhood roaming the wilds of Big Bend National Park and Far West Texas. After graduating high school, I worked for the National Park Service as a Wildland Firefighter and Fire Ecologist, as well as an Archaeology Intern at the Center for Big Bend Studies at Sul Ross State University. I graduated with my B.S. in Anthropology from Texas State University in May of 2015, and continued working for the CBBS and NPS for a while. When the opportunity arose to work with the 2017 Eagle Nest Canyon Expedition, I jumped at the chance. I had fallen in love with the Lower Pecos Canyonlands after several childhood canoe trips on the Devils and Pecos rivers. I knew it would be an adventure steeped in the rich archaeological history of the LPC as well as a means to improve my abilities and knowledge of the technology and techniques used in my field. I’m excited to expand my archaeological horizons as a Rockshelter Restoration Archaeologist with the 2017 Expedition!

Michelle Poteet

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Michelle Poteet

Hello everybody. I was born and raised in Oklahoma, but I have roamed around quite a bit throughout my lifetime. I even spent several years studying in Japan before I came back to my home state to pursue my higher education. At the University of Oklahoma I earned my B.A in Anthropology while focusing on archaeology and paleoethnobotany. For more hands-on experience I worked at the Oklahoma Archaeological Survey for three years as well as both volunteered and worked on field projects in the state.

A beautiful new environment, high levels of preservation, use of new technologies, and the chance to work on a preservation project much larger in scale than anything I had yet to take on are what drew me to the 2017 Eagle Nest Expedition. Getting to join in on an archaeological field academy and hiking and bouldering in such a scenic area on a daily basis have been an unexpected bonus. I look forward to the rest of the project, logistical challenges and all!

Eagle Cave 2017: Where We Stand

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The 2017 ENC Core Crew

During the first four weeks of the 2017 season the crew carried out last minute sampling within Eagle Cave, focusing predominantly on collecting matrix samples for archaeoentomology (bugs) samples (see Archaeoentomology?). Once we finished collecting our final few samples (including helping Charles Frederick collect nighttime OSL samples), it was time to begin the Eagle Cave Refill Challenge. We began backfilling operations last week, and have thus far moved about 1/6 of the imported fill (7 dump trucks worth). While the previous sentence sounds simple enough, we have been on a roller coaster ride of highs and lows, complex logistical problems, and hard labor.

We are excited to share our backfilling adventure with you this spring, stay tuned for more blog posts detailing the backfilling operation.  You can follow the action on the ASWT  Facebook page.

 

Zone VI: Into the Eagle Cave Unknown

Zone VI: Into the Eagle Cave Unknown

By Charles Koenig

Since we began excavating the main trench in Eagle Cave in 2014, we have always had some idea of what to expect thanks to the previous work by the 1963 University of Texas excavations.  In 1963, Mark Parsons and Richard Ross spent three days illustrating the north wall of the “Old Witte Trench.”

VV167-E-W-profile

Digitized and colorized field illustration of the 1963 Eagle Cave profile drawn by Mark Parsons and Richard Ross. The deep column in the center was added several months after the upper profile was annotated. Many more lenses, layers, and levels were noted on this profile than made it into the simplified, published version below. Original scan courtesy of the Texas Archeological Research Laboratory.

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Version of the profile that appeared in Ross’s 1965 Eagle Cave report. Only the major stratigraphic zones are noted.

Even though they did not record nearly as many “zones” and “lenses” as we have documented strats (units of stratification), we can correlate some of the 1963 stratigraphic zones to 2015/2016 strats because they took the time to illustrate and describe the different layers. Broadly speaking, UT recorded 6 major stratigraphic zones (1-6), in addition to many other lenses and layers within zones. In Zones 1-5, UT recovered a variety of cultural debris (chipped-stone tools, plant and animal remains, and our favorite – burned rock), and the earliest deposits in Zone 5 were dated to 6500-7000 B.C. (Ross 1965). However, they stopped excavating at the top of Zone 6 because it was considered a “sterile layer of yellowish limestone spalls and dust.”

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One of the 1963 Eagle Cave crew members beginning to dig the deep test through “sterile” fill. The white sediment at the man’s feet is Zone 6. View is looking west. Image courtesy Texas Archeological Research Laboratory.

From the outset of our work in Eagle, we have been guardedly optimistic the deposits from Zone 6 and deeper might not be sterile, but simply UT did not excavate far enough to find the next layer of cultural material. In reading the site journal for the 1963 work, we realized the UT crew stopped excavating at Zone 6 not only because they interpreted it as being sterile, but also because they simply ran out of time to excavate any deeper. They did sink a deep test to bedrock at the end of their work, but this was quickly excavated, and from what we can gather, they did no detailed recording or screening of materials that came out of this test. So, as we began excavating into the top of Zone 6 at the end of our last session (the last week in March) we were excited because we knew from that point down we would be excavating into the unknown – the oldest (>9000 years), minimally explored deposits within Eagle.

STrench_UTZones

South trench in Eagle Cave profile as of 4/17/2016. Top image is just of the orthophoto of the trench, and the bottom is the same image superimposed with our interpretation of UT Zones 1-6 .

First Contact

The first place we excavated into Zone 6 was towards the rear wall in the site. Several of us (Kelton, Justin, and myself) were excavating units to expose a profile section, when Justin uncovered a most surprising artifact: a thick fragment of what appeared to be bison long bone.

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Justin working in Zone 6 (white/yellow in profile).

In addition to the bison bone fragment, Justin also recovered two chunky biface fragments. After the months of anticipation, wondering what we may or may not find, and then to find artifacts and bison bone in one of our first units … we were excited, to put it mildly! As most things go on an archaeological site the bison bone find occurred on almost the last day of the field session, so we had to wait two full weeks before we could investigate Zone 6 again.

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The two biface fragments (top) and sizable bison bone fragment (bottom) recovered in Zone 6 towards the rear wall.

The Trench Floor

Even though we all wanted to jump right in to excavating Zone 6 and seeing what was there, the first thing we did when we got back to work was to devote several days to removing disturbed fill from the bottom of the trench. After completing this dusty, hot, exhausting job we had exposed intact stratigraphy across the entire bottom of the trench. And, by removing the disturbed fill, we exposed more or less exactly the floor of the 1963 excavations into Zone 6.

Before&After_F14

The crew removing disturbed fill from the bottom of the trench (left), and the top of Zone 6 exposed in the bottom of the trench (right).

Once we had the top of Zone 6 exposed across the trench floor, we laid out several units with the goal of excavating down in the trench floor to give us room to work as well as expose profiles on the south wall. However, after only excavating about 10 centimeters below where the UT excavations stopped our excavations slowed dramatically when we started finding bison bone fragments; lots of them.

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The scatter of bison bones as originally photographed in Unit 109.

Unlike the single bone fragment Justin found in the upper Zone 6 towards the rear of the site, Emily, Spencer, and Bryan began exposing dozens of fractured bison bones scattered over a 5 meter area. We knew we had something really cool, and that Zone 6 was definitely not sterile!

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The top surface of Feature 14 (fragmented bison bone scatter) as initially exposed in the Eagle Cave trench floor. The bison bones are slightly more yellow than the surrounding white/yellow rockshelter sediments.

Feature 14

As we continued to expose more and more bone, we realized these bone fragments were all related to one another and likely represent a single behavioral episode. Because of our working interpretation that the bones were fractured and strewn across the extant surface of the shelter in a single event, we gave the bone scatter the designation Feature 14 (the 14th formally designated feature recorded in Eagle Cave since 2014). The feature designation also means we wanted to take special care in how we went about recording the provenience of the bones. To do this we took a series of SfM models and shot in with the TDS many of the bones.

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Intermediate map showing Units 108 and 114 with additional bison bones exposed.

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Intermediate map showing Units 109 and 115 with additional bones exposed. The cluster of rock in the center of the image is Feature 15, a likely hot-rock thermal feature.

We were also very fortunate to have Art Tawater on hand that week as one of our volunteers. Art is a longtime member of the Texas Archeological Society and the Tarrant County Archeological Society, and one of his passions and areas of expertise is zooarchaeology. After the bones were mapped in (piece-plotted with TDS shots) and photographed, Art made a preliminary field ID for the various bones. This was a huge help because none of us (except Black) had any experience with excavating bison bones, let alone trying to figure out what element each bone fragment might be from!

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Art (left) helping Spencer (right) ID and package up bison bone for transport out of the site.

Mapping in the bones and collecting field observations slowed down the removal process, but we wanted to collect as much data in the field as we could so that when our collaborating zooarchaeologists Chris Jurgens and Haley Rush finally get to see the bones they will be well armed for the analysis to begin!  Plus, while the bones were well preserved, they had been purposefully fragmented originally  and some were crushed and cracked by the overlying deposits and did not remain intact upon careful removal.   Our detailed photographic record and Art’s field observations will allow a more complete analysis of the butchering and processing activities that took place on this surface over 9,000 years ago.

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One of the few diagnostic bones we recovered: a proximal left mandible (jaw) fragment from a juvenile bison with deep cut marks on the posterior side. This bone is visible in the Unit 109-115 image above.

Not Just Bone

In addition to the scattering of bison bone, we also found a modest amount of associated lithic debitage and stone tools. If you look closely several of the tools are visible in the above maps. It is telling that most of the chert artifacts appear to be made of only two or three cobbles judging from the matching colors and textures.  This bespeaks a short-term occupation during which only a few cobbles were knapped.

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Two bifacial tools found in direct association with the bison bone of Feature 14. Some of the debitage recovered appears to be the same raw material.

And although there is not the dense concentration of fiber within Feature 14 as in other areas of Eagle, we did recover some very badly decomposing organics.

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A decomposing piece of wood recovered during excavation of Feature 14.

And I also can’t forget to mention the possible hot-rock thermal feature (Feature 15) found at the east edge of the bison scatter, with bones above and below rocks that appear burned!

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Chalkboard shot of Feature 15, a likely hot-rock thermal feature in direct association with the scattered bison bones.

So What Does it All Mean?

We just finished excavating the main portion of Feature 14 earlier this week, so it is really too early to even say the analysis has begun, but we can at least offer up some of our preliminary observations and working ideas. Based on the how fragmented the bones are, we hypothesize Feature 14 represents a bison butchering and processing locale/event within Eagle Cave; possibly that of a single juvenile bison (portions thereof).

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The outline of all mapped bison bones (in black) superimposed onto the initial Feature 14 exposure. The most complete bone–a rib–was recovered at the boundary between Units 114 and 109. All the other bones are fragmentary.

Not only were most of the bones fragmentary, but very few had diagnostic (articular) ends left. In most cases, the field ID was either “medial rib fragment” (~90% of bones) or “long bone shaft fragment” (~8%) of the bones. The fragmented nature of the bones suggests that the people may have been trying to extract bone marrow or render grease from the bones after the meat was removed.

We also have some interesting horizontal distributions of certain artifacts and bones. The areas where we found the highest number of bones with cut marks overlaps with where most of the debitage is clustered. Bones with cut marks plus many flakes indicates this location was where people were cutting bone and/or meat and needing to resharpen their tools. It was also telling to find the relatively few burned bone fragments we found appear to have been concentrated around several thermally altered rocks and scattered charcoal!

41VV0167_Feature14_interpretation

Distribution/highest concentrations of burned bone, bones with cut marks, and debitage overlaid against the bone scatter.

We were also fortunate to recover a projectile point from the same layer as the bison bone. Although not directly associated, this dart point fragment was recovered just to the west of the majority of the bison bones and is made of a very similar dark chert material as much of the debitage.

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From top left: photograph of dart point fragment in situ; both sides of the dart point in the lab; map showing the location where the dart point was recovered in relation to the bison bone.

At the moment we are not ready to officially type the point, but it is a lanceolate, contracting stem dart point fragment that shares several attributes of Angostura points.

Where to from Here?

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Myself, Jack Skiles, and Steve ponder Feature 14 when it was first exposed.

The fact that we encountered Feature 14 as quickly as we did after beginning into the “sterile” deposits of Eagle Cave gives us hope for additional, older, cultural deposits below. We do not know how old the bison bones are at the moment, but we will be sending out radiocarbon samples soon. We have had a lot of fun excavating this intriguing feature, and we look forward to sharing new findings as we make them!

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The location of the Feature 14 bone scatter (linear cluster of yellow dots) and the original bison long bone fragment discovered towards the rear wall. We are excited by the prospects of what we may find as we go deeper into unknown Eagle Cave!

Micromorph Mania: A Microstratigraphic Approach to Evaluating Site Formation Processes at Eagle Cave

By Christina Nielsen, Charles Frederick, and Ken Lawrence

**This post is the second of several that give additional details regarding some of the different analyses that are currently being conducted with material from Eagle Nest Canyon.**

Tina standing by her poster at TAS.

Tina standing by her poster at TAS.

Eagle Cave (41VV167) is a large dry rockshelter with deeply stratified deposits spanning the Early Archaic through Late Prehistoric periods. My thesis research focuses on deposits in the northern sector of the shelter sampled during 1963 excavations by UT-Austin and again a half century later by Texas State University in 2014. My goal is to use multiple lines of evidence to evaluate the natural and cultural formation processes that resulted in the complexly stratified, culturally rich deposits present in Eagle Cave.

Plan view of Eagle Cave showing the location of the 5 Profile Sections excavated in 2014.

Plan view of Eagle Cave showing the location of the 5 Profile Sections excavated in 2014.

Our ongoing analysis involves a robust geoarchaeological sampling strategy that included the collection of micromorphological (micromorph) samples from Profile Sections (PS) 3 and 4 in Eagle Cave. This poster highlights the benefits and difficulties of collecting micromorph samples from fragile rockshelter deposits and shows how the analysis of the resulting slabbed samples and thin sections can aid in evaluating site formation processes.

Profile Section 3 and 4 excavations in Eagle Cave in 2014. Photos taken after initial recordation and sampling, but prior to geoarchaeological sampling.

Profile Section 3 and 4 excavations in Eagle Cave in 2014. Photos taken after initial recordation and sampling, but prior to geoarchaeological sampling.

Methods

Field Collection

  • Section of profile cut back to expose block of matrix
  • Block carefully removed, wrapped in toilet paper, tightly wrapped in tape, and labelled with provenience information,orientation, and north arrow
  • Sample placed in plastic Tupperware or sturdy container
  • Sample impregnated with polyester resin made from polyester, styrene, and methyl ethyl ketone peroxide (MEKP)
Charles Frederick collecting micromorphological samples from PS4 in Eagle Cave in spring 2014.

Charles Frederick collecting micromorphological samples from PS4 in Eagle Cave in spring 2014.

*The micromorph samples were carefully carried out of the canyon and up to Jack Skiles’ shed located a few hundred feet from Eagle Cave. Had the impregnation happened further from the shelter, these friable samples would have been far less successfully embedded.

Dan Rodriguez impregnating micromorphological samples with MEKP in Jack Skiles’ shed.

Dan Rodriguez impregnating micromorphological samples with MEKP in Jack Skiles’ shed.

Slabbing

  • After completely solidified, sample removed from container and north orientation notched in block
  • Outer casing removed using oil-based rock saw to expose intact soil block
  • Each side of block is scanned using high resolution
  • Block is cut into 1cm slabs for thin section production, curation, and macroscopic analysis
  • 4 x 6cm sections cut from slabs to be sent to Spectrum Petrographics, Inc. to be made into thin section slide

 Sampling

The sampling strategy was fairly simple: capture as many stratigraphic layers (strats) as possible within the PS3 and PS4 profiles. As archaeological and geoarchaeological sampling had already occurred prior to the micromorph collection, some strats identified during the initial profile recordation were no longer visible in the profile.

Summary of Micromorphological Samples from PS3 and PS4 in Eagle Cave

Summary of Micromorphological Samples from PS3 and PS4 in Eagle Cave

Specific types of strats that were especially important to capture in the micromorphs included microstratigraphy such as thin lamina and lenses as well as strats that were associated with cultural features. Using this strategy, the 13 relevant micromorph samples captured approximately 27 of the 85 total stratigraphic layers identified in the field. A total of 22 thin section slides were made then from the 13 micromorph samples.

Micromorph sample MM1 from PS3A (FN 30744). This micromorph slab was cut into three 4 x 6 cm blocks to be sent off and made into thin section slides (denoted by red boxes). The three sections were numbered FN 30744-1 through 30744-3. High resolution scans of each of the resulting thins section slides are presented on the right. Thin section analysis is currently underway.

Micromorph sample MM1 from PS3A (FN 30744). This micromorph slab was cut into three 4 x 6 cm blocks to be sent off and made into thin section slides (denoted by red boxes). The three sections were numbered FN 30744-1 through 30744-3. High resolution scans of each of the resulting thins section slides are presented on the right. Thin section analysis is currently underway.

Thin section slide 30744-1 from PS3A. This thin section correlates to strat S40 and S41. S40 was initially recorded as a light gray ash deposit and S41 was characterized as a thin, white ash lens. From the micromorph block and thin section, you can see that these deposits look far different from how they appeared in profile. S40 has a fairly dense concentration of charcoal as well as fragments of shell and rock

Thin section slide 30744-1 from PS3A.
This thin section correlates to strat S40 and S41. S40 was initially recorded as a light gray ash deposit and S41 was characterized as a thin, white ash lens. From the micromorph block and thin section, you can see that these deposits look far different from how they appeared in profile. S40 has a fairly dense concentration of charcoal as well as fragments of shell and rock

Thin section slide 30744-2 from PS3A. This thin section contains the lower boundary of strat S42 and S43. S43, was also recorded as an “ashy” layer, but does not appear so in thin section. Similar to S40, numerous charcoal and rock fragments are visible in thin section.

Thin section slide 30744-2 from PS3A.
This thin section contains the lower boundary of strat S42 and S43. S43, was also recorded as an “ashy” layer, but does not appear so in thin section. Similar to S40, numerous charcoal and rock fragments are visible in thin section.

Thin section slide 30744-3 from PS3A. This thin section possibly correlates to strat S51, which was recorded as an animal burrow. In thin section, this looks very similar to S43 and may have been misidentified during micromorph collection. S51 may have been completely removed during initial sampling. Additional analysis needs to be done to identify whether post-depositional processes are present.

Thin section slide 30744-3 from PS3A.
This thin section possibly correlates to strat S51, which was recorded as an animal burrow. In thin section, this looks very similar to S43 and may have been misidentified during micromorph collection. S51 may have been completely removed during initial sampling. Additional analysis needs to be done to identify whether post-depositional processes are present.

 

 

Benefits

The deposits in Eagle Cave, like many other Lower Pecos rockshelters, are very dry and have a loose consistency. This posed many challenges during initial recordation of strats and with the subsequent geoarchaeological sampling. Profile Section walls became enveloped in a film of dust with the slightest breeze or movement. Despite efforts to clean walls prior to all documentation, observations during strat recording were somewhat hindered by the persistent dust. The collection and analysis of micromorph samples, however, allows for a clearer examination of stratigraphy and the relationships between various deposits. Characteristics that aid in deciphering formations processes, such as boundaries between strats, are especially difficult to determine when obstructed by dust. Thin sections made from the micromorph samples can provide information crucial to the study of formations processes such as the size, orientation, sorting, and mineral composition of grains, organics, and artifacts as well as post-depositional disturbances of sediments.

Challenges

Since the micromorph samples in PS3 and PS4 were collected after all other sampling had been completed, it was sometimes difficult to correlate the samples with the strats initially identified in the field. In hindsight, ideally the micromorph samples should have been collected immediately after the strats were identified and documented to allow for a more accurate correlation.

Field collection is also not always successful in loose deposits such as these and many first (and second) attempts at collection failed. Patience and perseverance are necessary qualities to have in this type of setting. The entire micromorph process, from collection to analysis, is a lengthy one but the potential information that can be obtained from this type of analysis greatly outweighs the challenges you may face along the way.

Left: Annotated SfM image of PS3A depicting stratigraphic layers identified during initial recordation; Right: Micromorph block MM1 ready to be removed from profile PS3A. MM1 collected from area where strats S40-42 and S51 were initially recorded, but as you can see, the strats do not quite look like how they did prior to sampling. Note: In situ, many of the strats look like ash deposits. However, as you can see from the MM1 block these “ashy” deposits are not in fact ash, but have a dark-colored matrix with large quantities of rock, charcoal, and other inclusions. The dusty field conditions make it difficult to characterize the strats with a high level of accuracy during initial recording.

Left: Annotated SfM image of PS3A depicting stratigraphic layers identified during initial recordation; Right: Micromorph block MM1 ready to be removed from profile PS3A. MM1 collected from area where strats S40-42 and S51 were initially recorded, but as you can see, the strats do not quite look like how they did prior to sampling.
Note: In situ, many of the strats look like ash deposits. However, as you can see from the MM1 block these “ashy” deposits are not in fact ash, but have a dark-colored matrix with large quantities of rock, charcoal, and other inclusions. The dusty field conditions make it difficult to characterize the strats with a high level of accuracy during initial recording.

Conclusion

Long inhabited limestone rockshelters with deeply stratified deposits, such as Eagle Cave, can be difficult for an archaeologist to interpret. The natural degradation of the shelter itself, combined with human modification and natural forces create often complicated stratigraphic deposits. My thesis research involves a multidisciplinary approach to evaluate the formation processes evident in PS 3 and 4. The ongoing analysis of the micromorph slabs and thin sections from this sector of the shelter will help elucidate some of these complex processes and contribute to the overall analysis of formation processes in this sector of the shelter.

**A PDF version of this poster is available here: Nielsen_Micromorphs_TAS2015_FINAL

Paleofeces at Eagle Cave: A Preliminary Report of Ongoing Research

Paleofeces at Eagle Cave: A Preliminary Report of Ongoing Research

**This post is the first of several that give additional details regarding some of the different analyses that are currently being conducted with material from Eagle Nest Canyon.**

Steve Black stands next to the coprolite poster at TAS.

Steve Black stands next to the coprolite poster at TAS.

By Stephen L. Black, Emily R. McCuistion, Matthew E. Larsen, and Chase W. Beck

The 2015 Ancient Southwest Texas Project excavations were the first to document paleofeces (coprolites) in Eagle Cave. During the original site excavations in the 1930s and 1960s no coprolites were reported (even though substantial amounts of paleofeces were likely encountered). Therefore, while not completely unexpected, we were pleasantly surprised when we uncovered the first coprolites.

Extreme care was taken as we excavated these fragile organic remains. Rocket bulb air puffers were used to remove sediment from around in situ specimens. After in-field photography, paleofeces specimens were point provenience with a Total Data Station and/or Structure from Motion (SfM) before being carefully removed and bagged without handling. Specimens were transported to the field laboratory in boxes or by hand to avoid crushing. Temperature extremes were avoided and bags were vented if moisture condensed in the bags.

(Left) Paleofeces in association with faunal remains. (Center) Emily McCuistion using a rocket bulb to gently poof sediment away from a coprolite. (Right) Coprolite on a rock in situ. Another is visible in the profile.

(Left) Paleofeces in association with faunal remains. (Center) Emily McCuistion using a rocket bulb to gently poof sediment away from a coprolite. (Right) Coprolite on a rock in situ. Another is visible in the profile.

Preservation

Preservation conditions of all archaeological material varied across the site. Ironically, the best observed preservation was towards the dripline, whereas the worst was towards the backwall of the shelter. This was true for all non-carbonized organic remains, not just paleofeces. However, even within the well-preserved areas of the site there is differential preservation between individual specimens.

We are still exploring why preservation changes across the site, but some factors affecting preservation became clear when a small sample of coprolites were analyzed in the lab at Texas A&M. Of these, many were fragmentary and exhibited insect bore-holes and vacuoles, suggesting gaseous release before desiccation. Upon microscopic analysis, due to the poor condition of some coprolites the pollen was poorly preserved, and degraded, folded, and torn grains prevented the completion of a standard analysis.

There are distinctive differences between a well-preserved coprolite (top) and a poorly preserved coprolite (bottom).

There are distinctive differences between a well-preserved coprolite (top) and a poorly preserved coprolite (bottom).

Distribution of Paleofeces

Over 120 coprolites were point-provenienced during the 2015 field season. The majority of these specimens were excavated from the front of the rockshelter and approximately a meter below the surface. At Eagle Cave the coprolites are mainly found in areas of discarded fire-cracked rock and plant remains (cut leaf bases and other fiber). Sometimes they are found within compacted and dry-cracked sediment, which we sampled and hypothesize may be evidence of urine-soaking.

Locations of point-provenienced paleofeces samples from Eagle Cave.

Locations of point-provenienced paleofeces samples from Eagle Cave.

Paleofeces Variation

A representative sample of Eagle Cave coprolite sizes, colors, forms, and preservation states. All coprolites are displayed to scale.

A representative sample of Eagle Cave coprolite sizes, colors, forms, and preservation states. All coprolites are displayed to scale.

SIZE

Size is affected by several conditions, including length of time since the last bowel movement and the types of food eaten. Meals based on a single type of food can result in smaller stools, though a vegetarian diet can result in a larger stool than an omnivorous diet.

SHAPE

Previous paleofeces studies have found that plump, shapely coprolites are often from a fiber/plant-heavy meal while the “loose” ones may be from an individual who had recently consumed a lot of meat. There are, however, many other reasons that one could have had fluid bowel movements including parasites, water containing algae-born toxins, plants with a laxative effect (like lechuguilla and sotol), and even an individual’s emotional state.

COLOR

Color can be indicative of diet; the darker specimens often result from meat consumption while the lighter ones can be indicative of a vegetarian and/or carbohydrate-rich meal. When dried, however, colors change. Nonetheless, it is interesting to note color variations.

Preliminary Analysis

Field Lab Observations

Botanists and faunal experts can identify large plant and animal remains within coprolites. Thorough analysis requires rehydrating the coprolite and separating it into constituent parts. Sometimes, however, macrofossils are visible on the surface. In the field lab, Emily McCuistion observed several plant and animal remains while photographing specimens. Observable in the photos to the right are a rather large bone fragment from a jackrabbit-sized creature, as well as numerous seeds, including mesquite and prickly pear.

Macrofossils observed in Eagle Cave coprolites. Clockwise from top-left: a mesquite endocarp in a coprolite fragment; jackrabbit-sized bone embedded in a coprolite; and unidentified seeds in a coprolite.

Macrofossils observed in Eagle Cave coprolites. Clockwise from top-left: a mesquite endocarp in a coprolite fragment; jackrabbit-sized bone embedded in a coprolite; and unidentified seeds in a coprolite.

Laboratory Analysis

Ten samples were sent to Texas A&M University for a preliminary study of Eagle Cave paleofeces conducted by Chase Beck. These specimens varied greatly in size, completeness, and preservation. When conducting the analysis of the ten specimens, some contained no coprolitic material, some contained mixed coprolitic and non-coprolitic material and some seemed to be multiple broken piece of coprolites which could not be re-assembeled into a whole.

Microfossils observed in Eagle Cave coprolites (from left): unknown Liliaceae phytolith; sotol phytolith; and an unidentified phytolith.

Microfossils observed in Eagle Cave coprolites (from left): unknown Liliaceae phytolith; sotol phytolith; and an unidentified phytolith.

Five specimens were selected for further analysis. These were hydrated and sieved, and then the material was separated. While the coprolites had some evidence of bone fragments, there was no hair. The majority of material in the coprolites was botanical in nature. Seeds, pollen, calcium oxalate crystals, druse crystals, plant fibers, and phytoliths were all observed. Sotol was the most common pollen grain observed, but other taxa were also present. The presence of calcium oxalate and druse crystals has been linked in the past to the consumption of prickly pear cactus pads. Some of the phytoliths observed are associated with various grass species (Poaceae). The stylus phytoliths are likely sotol (Dasylirion spp.) or agave (Agave spp.). The seeds observed are tentatively identified as sumac (Rhus spp., likely Rhus virens).

Microfossils observed in Eagle Cave coprolites (from top): calcium oxalate crystals found abundantly in prickly pear cactus; stylus phytolith indicative of lechuguilla or sotol; and raphide crystals common in both sotol and lechuguilla.

Microfossils observed in Eagle Cave coprolites (from top): calcium oxalate crystals found abundantly in prickly pear cactus; stylus phytolith indicative of lechuguilla or sotol; and raphide crystals common in both sotol and lechuguilla.

Future Study

Matthew Larsen uses sign language to indicate he has discovered another coprolite.

Matthew Larsen uses sign language to indicate he has discovered another coprolite.

Avenues of future analysis include studying macrofossils, pollen, phytoliths, parasites, DNA, radiocarbon dating, and comparison studies with paleofeces from other sites, such as Hinds Cave.

Although the first samples proved too degraded for full analysis, hope remains that DNA may provide more in-depth information. Better preserved samples may be more conducive to future full analysis as well.

The oldest units opened at the end of the 2015 field season are showing some excellent preservation and there are high hopes for more coprolites in the 2016 field season.

A full PDF version of the poster is available here: Blacketal_TAS2015_Paleofeces

Eagle Cave South Trench 2015: Initial Observations from Profile Section 15

**This is the final of four blog posts showcasing a different Profile Section that was documented and sampled during the 2015 field season. Each of these Profile Sections has different sediment characteristics, artifacts, and ecofacts. Profile Section 15 is located closest to the dripline. For a location map see 2015 Investigations at Eagle Cave.**

Victoria stands beside her poster at TAS.

Victoria stands beside her poster at TAS.

By Victoria Pagano

The 2015 field season of the ASWT Project in Eagle Cave revealed interesting stratigraphy and preservation in the south trench profile. This poster presents the preliminary findings from PS15, a fiber-rich profile section located on the east side of the trench close to the dripline. The profile has unique preservation of mixed fiber and other organic remains, a stark contrast to the remains of later depositional events further towards the back wall of Eagle Cave. Within the PS15 fiber zone are dense concentrations of fire cracked rock layered almost entirely throughout. Interestingly, PS15 revealed numerous coprolites, several nearly complete lechuguilla central stems, and other perishable artifacts — such as faunal remains and fiber artifacts, but very little chipped or ground stone tools. PS15 may represent a different suite of activities than what is preserved at other sections of the trench. Various samples — C14, geomorph, soil — were collected as the profile was described and photographed for 3D-modeling.

Fully exposed, pre-sampling orthophoto of PS015.

Fully exposed, pre-sampling orthophoto of PS015.

Assigning Strat Numbers

Strat (stratitraphic layer) numbers were assigned following the natural stratigraphy seen in the profile face. If a identified in one profile section is clearly present in adjacent profile section, it was assigned the same strat number. The thick FCR zone that slopes down towards the dripline was subdivided into three strats, in order to sample visible content variation. During analysis, strats can be combined as necessary.

Field annotation (top) versus digital annotation (bottom) of PS015. The field annotation has all the sample locations (geomatrix, C14, spot, and coprolites) plotted.

Field annotation (top) versus digital annotation (bottom) of PS015. The field annotation has all the sample locations (geomatrix, C14, spot, and coprolites) plotted.

PS15 Strat Definitions

S0262 Compact, broken down fiber w/scattered FCR.
S0263 Tapering, thin gray ash layer.
S0264 Mildly compact matrix with larger pieces of fiber, charcoal, and some FCR present.
S0265 Thin strat of ash and charcoal present in only the eastern 1/3 of profile.
S0266 Western FCR zone; large pieces of botanic remains (seeds, lecheguilla, sotol), charcoal, and coprolites.
S0267 Central FCR zone; pieces of botanic remains (seeds, lechuguilla, sotol), and coprolites. This section is more compact than S0266.
S0268 Eastern FCR zone; more gritty, fine fiber matrix and mixed FCR with smaller pieces of botanic remains than S0266 or S0267.
S0269 East sloping strat of semi-compact gritty, broken down fiber matrix; small amounts of FCR mixed with pieces of fiber and charcoal.
S0270 Charcoal–burned seeds and wood– and pieces of flat fiber, possibly sotol or lechuguilla cut leaf bases.
S0271 Compact organic, broken down fiber layer present only in the SE corner.
Victoria discussing PS015 with landowner Jack Skiles.

Victoria discussing PS015 with landowner Jack Skiles.

 

Excavation Methods

Half of PS15 was sampled by units 66 and 63. All matrix was collected;  any artifacts were shot in and collected. Both units were excavated followed the strats defined on the profile face.  For record keeping and maintain proper provenience between the two units, Unit 66 strats were excavated as “layers” rather than “strats.”

The profile face was sampled by collecting targeted spot, geomatrix, and 14C samples, before the sampling column units were excavated.

Orthophoto of sampled strats and collected artifacts interpolated onto PS15. The artifacts are shown below.

A.) FN31874 – Remains of a sandal; B) FN32069 – Lechuguilla central stem; C.) FN31841 – Fiber knot; D.) FN31894 – Small, round cactus; E.) FN31861 – Large coprolite (115.16g): F) FN31860 – Two pieces of modified turtle carapace that re-fit.

A.) FN31874 – Remains of a sandal; B) FN32069 – Lechuguilla central stem; C.) FN31841 – Fiber knot; D.) FN31894 – Small, round cactus; E.) FN31861 – Large coprolite (115.16g): F) FN31860 – Two pieces of modified turtle carapace that re-fit.

Rocksort

Rocksort was performed in the field, this was accomplished by collecting any FCR greater than 1in. FCR was sorted according to size and rock type, then photographed and weighed. Any FCR not separated out was sieved out of the matrix samples in the field lab.

Rocksort photos showing 7.5-11 cm (left) and <7.5 & 11-15 cm FCR (right) removed from S266

Rocksort photos showing 7.5-11 cm (left) and <7.5 & 11-15 cm FCR (right) removed from S266

Preliminary Data

(Left) Total mass of FCR removed from each of the strats sampled in PS15. (Center) The amount of fiber and wood recovered from ½” sieve. (Right) Debitage count recovered from½” sieve.

(Left) Total mass of FCR removed from each of the strats sampled in PS15. (Center) The amount of fiber and wood recovered from ½” sieve. (Right) Debitage count recovered from½” sieve.

PS15 represents a different set of activities than what we see in other sections of the South Trench, and is characterized by higher densities of plant materials, charcoal, and FCR, as well as coprolites. The location of the profile so near the dripline at the front of the shelter in combination with so much organic material and semi-decent preservation, adds an interesting twist to the story of Eagle Cave.

**A full PDF version of this poster is available here: Pagano_TAS2015_PS15_FINAL

Eagle Cave South Trench 2015: Profile Section 12

By Emily McCuistion

**This is the third of four blog posts showcasing a different Profile Section that was documented and sampled during the 2015 field season. Each of these Profile Sections has different sediment characteristics, artifacts, and ecofacts. Profile Section 12 is located further towards the dripline than Profile Sections 9 or 17 For a location map see 2015 Investigations at Eagle Cave.**

IMG_5961

Emily standing next to her poster at TAS.

Profile Overview

Profile Section 12 (PS12) is located centrally in the south trench wall of Eagle Cave at a point of transition from superior preservation (just behind the shelter’s dripline) to increasingly fragmented organics and compacted sediments near the back of the shelter. The profile is characterized by dense fire cracked rock (FCR) from earth oven cooking capping alternating deposits of fibers (plant remains), FCR, and latrine deposits.

PS12

Profile Section 12 prior to sampling.

PS12_strats

Stratigraphic boundaries of Profile Section 12

Strat Descriptions

(Listed top to bottom)

  • S174: Disturbed, dominated by dense FCR.
  • S177: Dense FCR with ash and some fiber.
  • S229: Thin lens of burned fiber.
  • S230: Thin lens of “ashy” silt with little FCR.
  • S231: Thin lens of FCR in loose, “ashy” silt.
  • S232: Charcoal stained “ashy” silt; few FCR.
  • S233: Decomposed fibers in a silty matrix.
  • S234: Fiberous; possibly urine compacted.
  • S235: Lens of fiber and coprolites in silt matrix, extends only ~40cm into exposure. S272: Compact with irregular topography and some fibers; possibly urine compacted; overlaying or intermixed with FCR.
  • S236: Semi-compact “ashy” silt with few FCR, some fibers likely intrusive from S234.
  • S241: Small patch of fiber and coprolites.
  • S237: Dense FCR in a loose “ashy” silt.
  • S238: Thick fiber layer with scattered FCR.
  • S239: Originally thought to be intact but found to be disturbed during excavation.
  • S240: Originally thought to be intact but found to be disturbed during excavation.
  • S285: White “ashy” silt with crumbly limestone and FCR

 

Profile Sampling

Two sampling columns (Units 57 and 64) were excavated by stratigraphic layer (strat) in the eastern 2/3rd of the profile. When sampling strats individually was not feasible, several strats were combined into a unit-layer.

PS012

Layers excavated in sampling column units 57 and 64, re-projected onto PS12. Layer boundaries are based on the east-west midline of the units.

Data Summary

The graphs below present data from the sampling columns (Units 57 and 64). Note that data correlate imperfectly in the sampling columns as some strats were lumped together into layers during excavation, and other strats were not present in both sampling columns. An asterisk indicates that a strat was sampled individually in one unit, but was not sampled individually in the unit-layer listed in parenthesis. For instance, within Matrix volume, S229 and S232 were collected individually in Unit 64, but S230 was not present in Unit 64. In Unit 57, S229, S232, and S230 were collected as part of Layer 2.

PS12_MatrixVolume

Matrix Volume does not include FCR >1 inch. No Matrix collected from S174, S177, or S239.

PS12_FiberMass

Fiber mass is from ½” sieve.

PS12_FCRMass

FCR mass includes only FCR >1 inch. FCR data was not taken for S174.

PS12_Debitage

Lithic debitage count is from ½” sieve.

Artifacts

Artifacts found in sampling PS12 include a bone tool, a groundstone fragment, a wooden artifact with cut marks, 6 fiber knots and 2 strands of cordage, 2 biface fragments, 2 cores, 8 modified flakes, 3 painted pebbles, 19 manuports, 2 quids, 45 paleofeces or fragments of paleofece, and abundant faunal and botanical remains.

PS12_Artifacts

The Future of PS12!

Anticipated data and study includes radiocarbon dating, faunal, botanical, coprolite, pXRF, micromorph, residue and artifact analysis. PS12 has an important role to play in understanding site use, formation and preservation processes at Eagle Cave.

PS12_Excavators

Dr. Kevin Hanselka (left) annotates PS12 and Emily (right) excavating one of the two sampling columns in PS12.

**A PDF version of the poster is available here: McCuistion_TAS2015_PS012_FINAL

Eagle Cave South Trench 2015: Initial Results from Profile Section 9

By Matt Larsen

**This is the second of four blog posts showcasing a different Profile Section that was documented and sampled during the 2015 field season. Each of these Profile Sections has different sediment characteristics, artifacts, and ecofacts. Profile Section 9 is located adjacent to Profile Section 17 (see Cleaning the Kitchen at Feature 8). For a location map see 2015 Investigations at Eagle Cave.**

Matt standing next to his poster at TAS.

Matt standing next to his poster at TAS.

Profile Section 9 (PS9) is one of several profile sections along the south wall of the Eagle Cave trench. It differs from the other profile sections in that it is perpendicular to the main trench, and thereby provides a small area of different perspective. PS9, like many profile sections toward the rear of Eagle Cave, suffers from significant bioturbation.

PS9 with all strata demarcated as defined on-site. The areas marked with diagonal lines indicate the numerous krotovinas (back filled animal burrows), which complicate an already complex stratigraphy. 28 strata were defined in PS9, many of which were visible in the adjacent PS10. The strata are not numbered in order because some strata were defined originally in PS10 or PS5. In all, there were five strata description events. Areas of interest include a “striated wedge” of alternating light and dark strata in the upper right and the sudden appearance of dark charcoal rich strata in the lower half of PS9.

PS9 with all strata demarcated as defined on-site. The areas marked with diagonal lines indicate the numerous krotovinas (back filled animal burrows), which complicate an already complex stratigraphy. 28 strata were defined in PS9, many of which were visible in the adjacent PS10. The strata are not numbered in order because some strata were defined originally in PS10 or PS5. In all, there were five strata description events. Areas of interest include a “striated wedge” of alternating light and dark strata in the upper right and the sudden appearance of dark charcoal rich strata in the lower half of PS9.

 

Strat Descriptions

  • S0261 – Thick, white-gray ashy layer with small laminations.
  • S0260 – Relatively thin fiber layer with some ash, charcoal, and small (<5mm) pebbles.
  • S0259 – White-gray ashy layer with laminations.
  • S0258 – Thin horizontally bedded fiber/ash layer.
  • S0257 – Rather thin white ashy layer with possible small FCR inclusions.
  • S0256 – Light brown fiber layer with some ash and charcoal.
  • S0255 – Sloping white/gray ashy layer with some laminations.
  • S0254 – Rather faint gray white/yellowish layer of bedded fiber and ash.
  • S0253 – Thick white/gray ashy strat with FCR; slightly wedged shape in profile, thickening S->N.
  • S0252 – Horizontally bedded fiber and ash sloping down to the N.
  • S0251 – Light gray ashy compact strat sloping down slightly S->N.
  • S0060 – Dark, relatively thick organic layer; thickens as it continues N.
  • S0152 – Light ashy layer that thins as you move N across the profile.
  • Excavated Layer 1
    • S0194 – Brown organic/fiber/charcoal strat with darker layer in the middle.
    • S0195 – Thin layer of darker fiber chunks/charcoal.
    • S0196 – Compact light brown, fine-grained organics.
    • S0154 – Thin yellowish-white ash layer sandwiched; strat thickens S->N.
  • S0197 – Brownish gray fiber layer sloping down to the N.
  • S0198 – Very flaky dark, organic fibrous layer with burned plant material.
  • S0199 – Thin, compacted fiber/charcoal layer.
  • S0200 – Dark gray with chunks of charcoal. S0200 is the “pitfill” defined by the interface strat S0250.
  • S0250 – Interface strat (pit) sloping down from S->N, intruding into and originating from S0205 and filled by S0200.
  • S0205 – Thin, sloping ashy deposit whose top edge slopes sharply down to the N roughly 10 cm from S profile boundary.
  • Excavated Layer 2
    • S0206 – Thin, compact tan-grey deposit with charcoal flecks and decomposing fiber.
    • S0207 – A relatively thick layer of gray/brown ash with lots of charcoal and fiber.
  • Excavated Layer 3
    • S0208 – Thin ashy strat.
    • S0209 – Light grey-brown strat with gritty-ashy and fiber.
  • S0210 – Ashy strat with less charcoal than the overlaying “ashy” layers. S0286 – Brown charcoal and fiber rich strat with many small rocks.

 

Excavation and Sampling Strategy

Excavation Unit 58 (U58) was placed to sample all the stratigraphic units (strats) recorded in PS9. U58 was excavated strata by strata, unless individual strats were extremely thin, in which case several related strats would be combined into a layer. All artifacts and sample locations were point-plotted with a Total Data Station (TDS).

PS9 with all excavated strata defined. Several sets of strata were too small for individual excavation and excavated as a layer of related strata. All excavated strata and layers in the image are derived from SfM 3D models and projected on the profile section exactly as they were excavated with a margin of error measured in millimeters.

PS9 with all excavated strata defined. Several sets of strata were too small for individual excavation and excavated as a layer of related strata. All excavated strata and layers in the image are derived from SfM 3D models and projected on the profile section exactly as they were excavated with a margin of error measured in millimeters.

All of the sediment from U58 was collected as matrix samples. Rocks obviously larger than 2.5 cm were put aside, then weighed and counted on-site and in the field lab, then discarded once the data were collected. This data will help determine how many earth ovens were constructed in Eagle Cave.

In the field lab, each matrix sample was sifted through a ½ inch sieve, and all artifacts and ecofacts were collected and bagged by type. The remaining matrix was split into 1 liter samples, for curation and to send to various specialists for analysis.

Matt Larsen (left) and Bryan Heisinger (right) excavating Unit 5

Matt Larsen (left) and Bryan Heisinger (right) excavating Unit 5

Recovered Artifacts

Artifacts recovered from Unit 58 (lockwise from top-left): edge-modified flake, heat-shattered core, Langtry dart point, charred bone with residue.

Artifacts recovered from Unit 58 (lockwise from top-left): edge-modified flake, heat-shattered core, Langtry dart point, charred bone with residue.

Modified Flakes. Three modified flakes were collected in PS9.

Cores. Four cores were collected in PS9. Three appeared to be heat-shattered, apparently in situ.

Faunal Remains. Faunal remains in PS9 consisted of snail, various bone fragments, and two antler tine fragments. One bone tool fragment was also collected.

Projectile Points. Three points were collected in PS9: a Frio, a Langtry, and an unidentified fragment.

Debitage. Debitage was collected from ½ inch sieve and was found throughout most of U58, as can be seen in the chart below.

PS9 Debitage

Rocksort. The largest amount of rocks came from strata S0261 and S0254, as can be seen in the chart below; these were also the most voluminous strata excavated. The rocks collected in PS9 tended to be fewer and smaller than in other areas closer towards the dripline.

PS9 Rocksort

This chart shows the rocksort mass, fiber mass, and the remaining matrix mass as percentages of the mass of the entire strat or layer. This provides a clearer picture of how much burned rock was in a strat as a proportion of the whole. The only fiber was 1.65 g collected from the ½ inch sieve in the stratum S0268 matrix. This is the lowest strat in the profile and may signify the beginning of a fiber and botanical rich zone similar to that seen in PS12.

This chart shows the rocksort mass, fiber mass, and the remaining matrix mass as percentages of the mass of the entire strat or layer. This provides a clearer picture of how much burned rock was in a strat as a proportion of the whole. The only fiber was 1.65 g collected from the ½ inch sieve in the stratum S0268 matrix. This is the lowest strat in the profile and may signify the beginning of a fiber and botanical rich zone similar to that seen in PS12.

Preliminary Analysis

Intern and Archaic chef, Emily McCuistion (top) watches the fire we created to heat the rocks for an experimental earth oven and (bottom) places lechuguilla and sotol hearts on top of the prickly pear packing material in an experimental earth oven.

Intern and Archaic chef, Emily McCuistion (top) watches the fire we created to heat the rocks for an experimental earth oven and (bottom) places lechuguilla and sotol hearts on top of the prickly pear packing material in an experimental earth oven.

PS9 appears to be located in an area of Eagle Cave used for repeated earth oven events over the centuries. Only a meter to the west are the remains of a hot rock feature (Feature 8) with ash and coal directly under the rocks, as would be expected in an earth oven bed (heating element).

PS9 itself has many strata varying between fiber or charcoal rich strats and strats that have a higher volume of ash. In these “ashy” strata are also organic remains burned to white ash as well as several heat-shattered chert cores. Strat S0250 is a distinct stratigraphic interface, which appears to be a pit dug into the material beneath, and filled in with contrasting matrix.

The lack of large amounts of FCR, relative to the areas closer to the dripline, seems to indicate the area in which PS9 is located was favored for earth oven pits and cleaned out by tossing spent rocks (and fiber) out towards the dripline.

 

**A full PDF version of the poster is available here:Larsen_TAS2015_PS009_FINAL**