P.I. Eyes Eagle Progress

By Steve Black

Over Spring Break last week I spent several days at Eagle Cave eying progress. The 2015 season is the first time since the inception of the ASWT research program in 2009 that I’ve worn only one hat, that of principal investigator (P.I.). Until this season I have also been the field director, meaning I was responsible for making most of the day-to-day strategic field decisions, as well as setting the overall research agenda, organizing the endeavor, and arranging funding and logistics. And so I found myself in Eagle Cave on Thursday, March 20th looking at the ongoing investigations with field-fresh eyes.

I have learned from experience one of the most important things to have at any archaeological site is a comfy chair for the PI to sit in and enjoy the view.

I (Charles)  have learned from experience one of the most important things to have at any archaeological site is a comfy chair for the PI to sit in and enjoy the view.

Below is what I wrote in my field journal as I sat looking out from the back of the shelter in an almost comfortable camp chair. Other than minor spelling and punctuation edits and the added contextual explanations in italics, this is verbatim.

“Work continues apace in Eagle. The crew is now a well-oiled excavation machine—six different exposures—from closest to back wall: Bryan excavating Unit 50 in Strip 3, exposing Feature 8; Tory excavating Unit 49 which spans Strips 3 + 4; Emily strating PS13 in Strip 4; Kevin Hanselka strating PS12 in Strip 7; Lindsay cutting back 2nd step in Strip 8; and Larsen and Elizabeth excavating Unit 48 in Strip 9. Wow! The Strategist—field director Charles Koenig­—moves back and forth directing the symphony, making strategic decisions, keeping track of who is doing what, looking over shoulders.”

Kevin Hanselka (left) and Emily both were identifying and describing strats (individual stratigraphic layers) within PS12 and PS13, respectively.

Kevin Hanselka (left) and Emily both were identifying and describing strats (individual stratigraphic layers) within PS12 and PS13, respectively.

“Bryan now an old hand—more confident and capable—Charles assigns him tasks requiring greater independence and/or leading the interns to accomplish a given task.” [Bryan Heisinger served as an intern in 2014 and promoted to staff archaeologist this season.]

ASWT Staff Archaeologist, Bryan Heisinger, excavating Feature 8 - an earth oven central depression

ASWT Staff Archaeologist, Bryan Heisinger, excavating Feature 8 – an earth oven central depression

“Larsen also more confident and able—building on short season. [Matt Larsen was at student volunteer for final six weeks of 2014 season; he graduated from Texas State in December and this season he is a regular intern.] Today he also has field journal duty.” [The crew takes turns keeping the daily field journal.]

Larsen delicately excavates through a fiber/FCR layer.

Larsen delicately excavates through a fiber/FCR layer.

 

“Tory handles TDS well—she set it up at right height for level or slightly downward shots, but must get on her tip toes to shoot down to the lower units. She is primary TDS operator this session. [Victoria Pagano is a 2015 intern and has just been accepted into the graduate Anthropology program at Texas State starting in the fall. TDS = total data station, the machine set up over a datum that gives us precise 3D coordinates for any targeted spot. A different core crew member serves as the go-to TDS operator for each 3-4 week field session. ]

Tori running the TDS - "shooting" in everything from strats to matrix samples to coprolites.

Tori running the TDS – “shooting” in everything from strats to matrix samples to coprolites.

 

“Emily assigning FNs in tent—flurry of requests from team members, some for Strats (she went to assign her own FNs for PS13, but wound up issuing FNs for others), some for Unit Layers, Spots, and Matrix Samples.” [Emily McCuistion is the final 2015 intern. She has defined the Strats or stratigraphic units for Profile Section 13 and assigned each Strat a unique Field Number. We also assign FNs for each small Spot sample of characteristic matrix for each Strat, and all other types of samples we collect. Our documentation system requires precise book keeping and the FNs make it possible to link one kind of data to another. We have a tent set up at the back of the shelter on the downstream end where we keep the laptop used to assign FNs and various equipment we try to keep out of the dust.]

“Kevin Hanselka volunteering today—fresh eyes with archaeobot lens—he was assigned to define strats in profile section with numerous fiber lenses. He spots various new things including a dart point with its tip sticking directly out of the profile. Charles tries out ideas on Kevin—good give and take. Kevin often mentions what he learned from previous experience or from an article he has read. “Ok, so we have agave lechuguilla and …” [Kevin earned his Ph.D. at Washington University at St Louis where he studied under Gayle Fritz, one of the leading archaeobotanical scholars in North America. His dissertation research was on plant remains from the Sierra de Tamaulipas rockshelters that famed archaeologist Scotty McNeish excavated the late 1940s.]

Kevin telling the crew about different plant parts they are finding.

Kevin points to examples of different plant parts exposed in profile. TxState graduate student Amanda Castaneda looks on.

“This is why we really appreciate our visitors and volunteers—fresh eyes and questions. SLB joins a discussion of fiber production that Kevin links to a fellow Wash U grad student who based her dissertation research on ethnographic accounts from the Eastern Woodlands—weaving and basketry done in rockshelters + houses because in open the fiber dries out too quickly. Were such weaving activities also emblematic of LPC shelters? Related, the whole issue of H-G intensification—managing landscape resources such as lechuguilla fields. Lech harvested for fiber, beverage and food. Could possibly trim leafs without harvesting bulb. But wouldn’t the heavy use for food be a ready source of fiber?”

“Elizabeth and Lindsey are a bit more tentative—the latter now has some ENC experience, the former new to area, also here for Spring Break. Chas assigns both to work on outer strips where we are working to cut back to intact layers.” [Elizabeth Jaroszewski graduated from TAMU and was just accepted as a TxState graduate student beginning in the fall. Lindsey Vermillion is a TxState senior who volunteered during last six weeks of the 2014 season and has proven to be a quick learner and hard worker.]

Lindsay and Elizabeth screening sediment from their units, while the rest of the crew works in the background.

Lindsay and Elizabeth screening sediment from their units, while the rest of the crew works in the background.

“This is the balancing act the Strategist must juggle—who has the skill set for a given task—and how to keep everyone busy productively? Long trench with different steps, strips, units, and profile sections makes this possible. Core crew can now do everything so he [Charles] lets them follow through, intermittently or continuously, from strip to unit to PS, giving them a sense of ownership and taking advantage of specific experience/familiarity w/ any given area.”

[In laying out the “Strat System” in our 2013 Eagle Nest Canyon research plan I used the term “Strategist” for the position that archaeologists of my generation usually called “Field Director.”  And although in the intro to this post I claimed to have worn the hat of field director/strategist until this season, I have shared this role with my graduate students as they have taken charge of certain investigations as part of their thesis research projects.  I am sure I have intruded into their decision making rather more than was helpful at times.  But making the strategic call is one of the things I love most about being an archaeologist and I’ve sometimes found it hard to relinquish strategic control.  It does my heart good to watch my former graduate student Charles lead the charge with aplomb.]

“Sounds—conversations in various spots across EC—some of unrelated experiences, like those told at the Screening Station. Some work related—back and forth on TDS, FN assignment. Above ideas discussions. Charles explaining steps and making sure forms are filled out… ‘Larsen this evening I’d like you to …’ iPod with jazz playing softly in background…. ‘Looking.’ ‘Shooting.’ ‘Got it.’ “Next is 329 and 318….’ Footsteps, some loud some muffled….. Scrape of trowel hitting FCR….. Soft brushing sound emanates from billowing cloud of dust. Those wearing dust masks have muffled voices—I can’t understand, but crew seems to follow easily—practice and younger ears.”

Work scene on March 20, 2015. Field director Charles takes a break shoveling out disturbed matrix while keeping an eye on the crew.

Work scene on March 20, 2015. On far left field director Charles takes a break from shoveling out disturbed matrix while keeping an eye on the busy crew. On the far right Elizabeth holds a reflector board to improve the lighting on the area where Bryan is taking yet another round of SfM images.

[Added the next day] “Strategic decisions are often tough—no clear-cut best way when dealing with very complex stratigraphy—pits dug through pits, fill vs. primary thermal features, hard structure (FCR layers and concrete-like ash conglomerates) vs. soft ash and softer burrow fill, plus the many exposure faces (of strips, profiles and units).  With SfM we can adapt and change our minds, knowing that we can reassemble/stitch [the 3D models]. Still, flexibility isn’t easy.  Use of Strat System and FN essential. Record Keeping critical. ‘Tis a challenge!”

And that is the Eagle Cave 2015 progress as eyed by this P.I. I will admit that as I started to write most of the above in my field journal it dawned on me that ASWT blog readers might appreciate a look at the excavation scene at Eagle Cave. I had realized that at the moment I was superfluous – most of the crew knew what they were doing and Charles was doing a marvelous job directing the scene. I could sit back and take it in as a participant-observer.

A competent archaeological crew intelligently and diligently investigating a fascinating rockshelter in a remote corner of the natural and modern world is indeed a joyful thing for a principal investigator to behold. I’m already looking forward to my next trip.

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Adventures in the Ancient Lost City of the Rodents

Larsen hard at work.

Larsen toiling away in the Mines of Mole-ia.

By Matt Larsen

Hey y’all, I’m writing today about burrows – but I’m talking packrats not pack animals. If you don’t remember me, my name is Larsen, and I am a recent graduate of Texas State, and this is the first long-term archaeological project I have worked on. One of the things that surprised me when I first started excavating out here is the large number of burrows we encounter. The burrows range from small and winding to large and cavernous. In some places it feels more like we are exploring some vast ancient underground city created by small creatures. Was it miniature Yeti, a.k.a. Littlefoot? Nope, it’s burrowing rodents.

The focus of our Eagle Cave excavations this season is the south face of the trench originally created by the Witte Museum in the 1930s and widened by the University of Texas at Austin crew in the 1960s. When we began excavating we were attempting to cut through the surface disturbed material to intact deposits. As Emily and I excavated our first unit, we had to discontinue cutting south into the trench face because we ran into an extremely large burrow, which we started calling the “Badger Burrow”.

Charles attempting to curl up in "The Badger Burrow".

Charles attempting to curl up in the “Badger Burrow”.

In this same area, I was excavating back the face of the unit and came upon a burrow with a tail sticking out of it! I was somewhat startled by this as we had been joking about cutting into a badger burrow and having an angry badger jump into someone’s face. At first I thought it was a snake, but then I realized it was a hibernating lizard. I gently removed the lizard and moved it to a place where it would be safe from animals and archaeologists.  These burrows are good examples of today’s blog topic: bioturbation.

What is Bioturbation?

Bioturbation is the term archaeologists use for any disturbance of the ground by living things. These include plants and tree roots, rodents, reptiles, insects, worms and any other organism that delves into the ground. Bioturbation is an issue all archaeologists face in some form or another. So, how does bioturbation affect archeological digs?

Bill Murray isn’t the only one concerned with burrowing animals. Archaeologists are concerned with bioturbation because it alters the archaeological context (see Where Context is Crucial). As organisms move through the earth they can affect the archaeological record in several ways. First, and most obviously, bioturbation changes the stratigraphy. Roots and especially burrows move dirt around in the earth. Dirt that was down deep is brought up, dirt that was near the surface is carried down and earth can be moved all over as animals backfill their own burrows. In a Canadian study of pocket gophers it was estimated that, if one gopher at a time lived in a 10x20m area and digging activity remained constant over 200 years, approximately 25 metric tons of earth would be moved!

A pocket gopher.

Hello, Mr. Pocket Gopher, it’s your friend Mr. Squirrel.

Burrowing animals often move artifacts up in the ground. The gophers, for example, make burrows about 6-7cm wide. Anything they come across that is less than 6-7cm, such as tools or projectile points, will be carried by the gopher out to the surface or into a side chamber of the burrow.

Bioturbation can also cause artifacts to move down farther into the ground. Burrowing by animals can undermine artifacts, even artifacts much larger than the animal (like a grinding slab for example), which allows them to sink down in the earth.

Burrowing animals also have a tendency to bring things in to their burrow, such as food or nesting materials. This means that some objects may seem to be deposited by people, but in actuality were brought into the ground by animals.

The movement of earth and artifacts through bioturbation requires archaeologists to understand that just because an artifact is found in a certain stratum does not mean it was originally deposited at the same time as that stratum. It also means care should be taken in establishing an age for a stratum or an artifact.

The destruction of a stratum or the movement of artifacts are negative aspects of bioturbation, from an archaeological standpoint.  Bioturbation can also, however, be a positive thing. Bioturbation can be a tool an archaeologist uses to study the past.

Positive Aspects of Bioturbation

The organic things brought into a burrow can tell us a lot about the past. The plant and animal remains preserved in a burrow inform us about what kinds of plants and animals lived in the area at a certain point in time. Because plants and animals like certain kinds of conditions, such as temperature and precipitation, we can extrapolate what the climate was like in the area at that time as well.

I recently learned of another positive aspect of bioturbation while listening to the radio. There was a story about two archaeologists, one in England and one in Denmark, who were using moles to gather archaeological data. Both were analyzing things brought to the surface by moles at protected sites where the archaeologists were not permitted to conduct an excavation themselves.

A mole.

A mole (happily, not present in Eagle Cave!).

In Viborg, Denmark, Jesper Hjermind studies what moles dig up at the site of a medieval fort. The moles often bring up artifacts and pieces of brick. By analyzing these objects, Hjermind is able to determine the location of buildings at the fort. If there are many objects at a molehill, then that is where a building is underground. The story can be found at: http://cphpost.dk/news/moles-digging-in-the-name-of-archaeology.12859.html .

At the site of a Roman barracks known as Epiacum in Cumbria, England, Paul Frodsham is also not allowed to excavate because the site is protected. He sifts through the tailings at molehills to find artifacts from Roman times. While this does not give him a full picture of the archaeology at the site, it allows him at least a glimpse. The story can be found here: http://www.bbc.com/news/uk-england-cumbria-22363936 .

What all this tells us is that bioturbation is a fact of life for an archaeologist and it can be either a help or a hindrance depending on how it is approached.

Bioturbation at Eagle Cave

Common bioturbators of the region.

Common bioturbators of the Lower Pecos region.

So what does bioturbation mean for us on site in Eagle Cave? How do we recognize it? How does it hinder us and how does it help us?

At the surface in Eagle Cave, the main agents of bioturbation were sheep, goats, and people. Eagle Cave was used in the early 20th century as a convenient place to pen sheep awaiting shearing in the pens atop the cliff. This means that the surface was mixed up by their milling about and is heavily disturbed. Further, people visiting the site for nearly a century have picked, plucked, and scratched at the surface (and deeper) of Eagle. We surmise the strata from the Historic through the Late Prehistoric eras – the layers at the “top” of the shelter profile – are nearly completely destroyed.

When we excavate at Eagle Cave, we first clear away the disturbed surface layer to get to the intact deposits underneath. As we dig into these intact strata, the main agents of bioturbation are burrowing animals such as rodents, lizards, and insects. The burrows we find range from very small insect burrows to extremely large mammal burrows. Most burrows are from rodents and are, on average, about 7cm (~2-3 inches) in diameter. We are able to distinguish burrows from intact material in several ways.

PS010 is a nice example of different burrow sizes and shapes. Note the excellent color contrast in the central burrows.

PS010 is a nice example of different burrow sizes and shapes. Note the excellent color contrast in the central burrows.

First, we use visual clues to identify burrows.  We often have clear layers (e.g., alternating white, black, and gray bands of ash, charred fibers and the like), and whenever there is an interruption in the strat from a burrow, the contrasting colors stand out, like in the above photo.  We also often see nesting material in the burrow matrix, grass or straw, and sometimes there are pockets of cached seeds. In modern  burrows, we often find sheep and goat dung mixed in as well.

Plan view of Emily excavating a burrow.

Plan view of Emily excavating a burrow.

In plan view (looking down on a unit from above) we can often see the burrow as a linear track extending across the unit. In profile view (looking at a vertical surface from the side) we often see burrows as either a circle of material, a hole, or as a linear disturbance extending across a profile face.

Archaeological excavation is not just dependent on visual cues, like color changes, but is also an extremely tactile endeavor. When we hit a burrow, it usually feels very different under the trowel from the rest of the stratum. Most of the time the burrow material is exceptionally loose; the trowel just sinks right in several centimeters without any pressure applied by the excavator at all.

Bryan excavates a rodent metropolis.

Bryan excavates a rodent metropolis.

The deposits at Eagle Cave often have burrows in them, and it can be extremely frustrating for an archaeologist to work with strata that are more burrow than intact. When we began excavation this season, we were excavating near the back of the shelter and we had to move a lot of earth before we found intact deposits. As we were cutting back the trench face we finally had to stop because we came upon a burrow nearly a meter across, the aforementioned “Badger Burrow”. We are no longer excavating from this area (the far right unit in the photo to the right) to the back of the shelter because it is all the backfilled trenches of the excavations in the 1930s; which just goes to show that archaeologists can be proficient bioturbators as well!

While at times frustrating, the disturbed and burrow material does not go to waste. We screen samples of these disturbed sediments on-site and use the artifacts we find for educational purposes here and at Texas State University. We often find interesting artifacts within the burrow material, including two large bison teeth this season.

Bodilly, the Bioturbation Hedgehog, promotes awareness of bioturbation amongst archaeologists.

Bodilly, the Bioturbation Hedgehog, promotes awareness of bioturbation amongst archaeologists.

So, while these artifacts have no clear archaeological context, they do clue us in as to the types of artifacts we should find. And we retain rare items (like a mussel shell pendant we found this week). They are also exciting finds that keep us motivated and in good spirits!

In summary, bioturbation is a part of nearly every archaeological excavation. It is important for researchers to understand the role bioturbation plays in the formation of an archaeological site so we can accurately interpret the data from a site. Although bioturbation is often frustrating, it can also be helpful to an archaeologist if used as another means of gathering information. We try to keep this in mind here at ASWT when we come upon an area that is more burrow than strat and makes us feel more like rodentologists than archaeologists.