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

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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**

Eagle Cave South Trench 2015: Cleaning the Kitchen at Feature 8

By Bryan Heisinger

**The next four blog posts will each showcase 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. The first is Profile Section 17 and Feature 8, located closest to the rear wall. For a location map see the previous post, 2015 Investigations at Eagle Cave.**

Bryan standing next to his poster at TAS.

Bryan standing next to his poster at TAS.

During the Ancient Southwest Texas Project’s 2015 Eagle Nest Canyon Expedition, the crew uncovered and sampled Feature 8—an earth oven pit and intact heating element complex near the back of Eagle Cave (see Between a Rock and a Heart Place). The dense concentration of large fire-cracked-rocks (FCR) and charcoal within the pit are classic characteristics of earth oven baking. Further, many of the limestone rocks were large (11-15 cm) in size and inclined in a basin-shaped configuration at the base of the pit. The matrix that surrounded these fire-cracked rocks (FCR) was heavily organic, ashy, rich with dime-size charcoal chunks, and almost entirely absent of artifacts.

Plan and profile views of Feature 8 as originally exposed in Unit 25. Notice the large FCR, and how they are inclined towards the right.

Plan and profile views of Feature 8 as originally exposed in Unit 25. Notice the large FCR, and how they are inclined towards the right.

Digital Elevation Models (top) and orthographic photos (bottom) of Feature 8 during excavation of Unit 25 Layer 3. Contour interval is 2 centimeters. Elevations range from 980.138 meters (brown) down to 979.445 meters (blue).

Digital Elevation Models (top) and orthographic photos (bottom) of Feature 8 during excavation of Unit 25 Layer 3. Contour interval is 2 centimeters. Elevations range from 980.138 meters (brown) down to 979.445 meters (blue).

Methodology

After initially exposing Feature 8 in Unit 25, Units 50 and 55 were opened up as sampling units. The two units were excavated following natural stratigraphic layers, and matrix samples were collected from each layer. Back in the lab, each matrix sample was sifted through a ½ inch sieve and all artifacts and were collected and bagged by type. The remaining matrix was split into 1 liter samples for curation and further analysis by our various colleagues (archaeobotany, geoarchaeology, and entomology). All rocks greater than 2.5 cm were added to the Rocksort data. Profile Section PS17 is the east/west running profile of excavation units 50 and 55. After cleaning the profile, a 3D model was created using Structure from Motion (SfM) photography  and the stratigraphic layers (strats) were annotated on an orthophoto of the profile.

PS017 Profiles

 

PS017 Debitage

PS017 Rocksort

Preliminary Interpretations and Observations

Based on the densities of large FCR  (> 11-15 cm), organic soil, and heavy concentrations of charcoal,  PS17 appears to be located in an area of Eagle Cave that has been used for repeated earth oven events over the centuries, of which the Feature 8 pit is just the most recent iteration.

Some interesting observations:

1) Besides charcoal and other carbonized plant remains, there was no uncharred organic material in the Feature 8 complex.

2) 110 + kg of burned limestone rock from Feature 8 was counted and quantified from Units 50 and 55. Many of these rocks were >15 cm, indicative of the “pristine” rocks expected in an earth oven heating element.

3) The amount of large FCR in the PS17/ F8 area relative to the units closer to the dripline, indicate that this area was favored for earth ovens pits. The tossing of discarded rocks during cleaning episodes would have sent smaller rocks and fiber toward the dripline.

4)  A hard/cemented matrix was encountered in layer 3 of Units 55 and 50. The formation process and composition of this anomaly is awaiting further analysis.

 

**A full PDF version of the poster is available here: Heisinger_TAS2015_Feature8_FINAL