Starting at Rock Bottom

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Maximillian Copeland
5 years ago
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1 Starting at Rock Bottom At rock bottom of the Brushy Creek site s geological column lies the first clue to human habitation: A smelting and heattreating furnace, and mold, carved into Bed Ked: Figure 15 Feature I: Iron stained fill removed from the furnace cavity. Note Bed Ice remnants (dark gray) in the background, to the right hand side in this image. The exposed portions of Beds Ica, Ice and Igl erode rapidly during periods of heavy drainage, exposing underlying Bed Ked.

Figure 16 Feature I: Fill was removed from the

2 Figure 16 Feature I: Fill was removed from the furnace to what was initially thought to be the floor of the cavity. Note the heavily iron-stained fill, which contrasts to locally occurring soil. Local soils are comprised chiefly of black clay mixed with silt. Also note the iron-stained chert cobbles and fossilized shells removed from the furnace (at the top of this image).

3 Figure 17 Feature I: As fill continued to be removed, it was observed that the floor of the furnace had a depression. An in situ metallic nodule was observed as the remaining fill was removed.

4 Figure 18 Feature I: A close-up shot of the in situ metallic nodule, positioned at the mouth of the soon to be revealed blowhole. Note the heavy iron staining around the nodule.

5 Figure 19 Feature I: As research continued, it became apparent that a rounded, triangular blowhole was drilled into the bedrock, at the bottom of the furnace.

Note the iron deposits still intact at the bottom, left

6 Figure 20 Feature I: An image of the furnace cavity and ca. 3 of the blowhole thoroughly cleaned. Note the iron deposits still intact at the bottom, left hand side of the furnace. Several other heavy iron stains are apparent. Figure 21

Feature I: Close up of the blowhole at the bottom of the furnace. Note the charring at the opening of the vent (top, slightly left hand side in this image).

Figure 22 Feature I: Surface blowhole inlet in relation to the furnace cavity.

7 Feature I: Close up of the blowhole at the bottom of the furnace. Note the charring at the opening of the vent (top, slightly left hand side in this image). Also note the secondary carbonate deposits on the right hand side of the blowhole. Grains of sand are adhered to the furnace floor, to the left of the blowhole. Figure 22 Feature I: Surface blowhole inlet in relation to the furnace cavity. The surface blowhole inlet is drilled downward, at an approximately 25-degree angle relative to the surface, directly towards the bedrock underlying the furnace. It is assumed that the blowhole outlet, at the bottom of the furnace, was drilled straight down (ca. 90 degree angle relative to the surface), tapping into the underlying, surface blowhole inlet channel.

8 Figure 23 Feature I: Close-up of the surface blowhole inlet. Note the same rounded triangular outline, similar to the blowhole outlet at the bottom of the furnace. It is assumed that a chert or granite bit was hafted to a spear shaft and rotated, drilling a channel into the softer limestone.

9 Figure 24 Feature II: Partially cleared out mold cavity, carved directly into Bed Ked. The mold is located approximately 18 southwest of the furnace.

10 Figure 25 Feature II: Completely cleared out mold cavity. Note the lack of erosional smoothing on the floor of the mold, implying a rapid, and then continuous filling, from shortly after its creation and utilization, until present.

11 Figure 26 Feature II: Close-up of the carving on the mold cavity floor. Again, note the lack of erosional smoothing.

12 Figure 27 Features I and II: Relative spatial relationship between the furnace, surface blowhole inlet, and mold. The mold is carved into Bed Ked, at the southern valley margin, while the furnace and blowhole are carved into Bed Ked, in the valley bed, ca. 18 northeast of the mold.

13 Figure 28 Feature I: The furnace shown in relation to the exposed portion of Bed Igl, in the far background. Again, note intact Bed Ice to the right (dark gray colored), uncomformably deposited on underlying Bed Ked.

14 Figure 29 Geologic column previously positioned above the furnace and mold. Rapid erosion of this overlying strata has been brought on by aggressive, urban development along the creek s corridor in recent years.

15 Figure 30 Another view (looking northeast) of the dissected alluvium (cut bank) previously positioned above the furnace and mold. The creek is working itself north, downhill, into the original, ancient bedrock creek bed, eroding the topsoil off of the southern portion the dissected alluvium (point bar) in the process. The erosional processes have completely scoured ca. 300 meters of upstream alluvium off of Bed Ked.

16 Figure 31 Another view of the dissected alluvium, beginning at the top of Bed Igl and continuing up to the Late Holocene soil (Bed III).

17 Figure 32 Another view of the dissected alluvium, beginning at Bed Igl and continuing up to the Early Holocene soil (Bed II).

18 Figure 33 The lowest stratum within Bed Igl consists of iron-stained and charred cobbles. This stratum has been termed Bed Igl-Iscc

19 Figure 34 Stratum Igl-Iscc

20 Figure 35 Stratum Igl-Iscc

21 Figure 36 Stratum Igl-Iscc

22 Figure 37 Stratum Igl-Iscc

Figure 38 Increased erosional processes have completely scoured, to bedrock, ca. 300 meters of alluvium upstream of Unit Lima. View is to the northeast.

23 Figure 38 Increased erosional processes have completely scoured, to bedrock, ca. 300 meters of alluvium upstream of Unit Lima. View is to the northeast. Note the remaining westernmost edge of Lima-Igl, with the tangled roots of previously and currently existing trees (middle foreground of this image). In the right-hand background the white gravels of exposed Bed Igl (point bar) are visible. The furnace is positioned ca. 6 meters to the right of the exposed roots.

Figure 39 The erosional processes have completely scoured, to bedrock, Beds Igl, Ice and Ica, previously overlying the furnace and mold. View is to the southwest.

24 Figure 39 The erosional processes have completely scoured, to bedrock, Beds Igl, Ice and Ica, previously overlying the furnace and mold. View is to the southwest. A test trench was cleared in Unit Lima, Bed Igl, to confirm exposed Bed Igl had a firm floor. After the surface limestone and chert cobbles were removed, a firm floor was apparent.

25 Figure 40 Another southwest view from the exposed portion of Bed Igl (point bar), at Unit Lima. Note exposed and dissected Bed Ica, underlying Bed Igl, and deposited on Bed Ked, in the middle background of this image.

26 Figure 41 Figures 40 and 41 are unhighlighted and highlighted images showing the relevant geology in the immediate area of the furnace and mold. The red line highlights one of the new drains installed in early Two additional drains were constructed, one approximately 100 meters upstream from this drain, and the other drain, 200 meters upstream. The light green X marks the location of the mold. The dark blue X marks the location of the furnace. The yellow highlight traces the northern boundary of remaining Bed Ica. The light blue highlight traces the contours of the test trench, the trench establishing the firm stratum of remaining Bed Igl. The purple x marks the westernmost intact portion of the southern side of dissected Bed Igl. Approximately 2 meters to the right of the dark green x marks the westernmost, intact portion of the northern side of dissected Bed Igl. The overall view is to the southwest, upstream.

27 Figure 42 Remnants of Bed Ice cemented to underlying Bed Ked, approximately 6 meters downhill (north) from the furnace.

28 Figure 43 More remnants of Bed Ice cemented to underlying Bed Ked, approximately 6 meters downhill (north) from the furnace.

29 Figure 44 More remnants of Bed Ice cemented to underlying Bed Ked, approximately 6 meters downhill (north) from the furnace. Figure 45

30 More remnants of Bed Ice cemented to underlying Bed Ked, approximately 6 meters downhill (north) from the furnace. Figure 46 Close up of Bed Ice. Note the thermally altered piece of Edwards Gray Chert incorporated into the Bed Ice matrix.

31 Figure 47 Close up of Bed Ice. Note the thermally altered piece of Edwards Gray Chert incorporated into the Bed Ice matrix. Also note the possible human alteration of the chert.

32 Figure 48 Close up of Bed Ice.

33 Figure 49 Close up of Bed Ice. Note the piece of Edwards Gray Chert incorporated into the Bed Ice matrix.

34 Figure 50 Close up of Bed Ice. Note the thermally altered piece of Edwards Gray Chert incorporated into the Bed Ice matrix.

35 Figure 51 Close up of Bed Ice. Note the thermally altered piece of Edwards Gray Chert incorporated into the Bed Ice matrix. Also note the possible human working of the chert. Next is a progression of aerial views of Unit Lima, spanning from :

Figure 52 An aerial photo from 1985. Unit Lima is on the right hand side of the photo, just to the left of the circular, white dirt road.

36 Figure 52 An aerial photo from Unit Lima is on the right hand side of the photo, just to the left of the circular, white dirt road. Note there are large trees still completely covering the now dissected alluvium. This suggests that in 1985, there was no dissection, further evidenced by the lack of exposure of the underlying, bright white alluvial gravel from Bed Igl.

37 Figure 53 An aerial photo from Unit Lima is on the right hand side of the photo, just to the left of the circular, white dirt road. Note there are large trees still completely covering the alluvium. This suggests that in 1985, there was no dissection, further evidenced by the lack of exposed, underlying, bright white alluvial gravel from Bed Igl. The creek has not yet started to work it s way downhill through the alluvium, evidenced by the lack of diversion of the creek path (highlighted).

Figure 54 An aerial view from 1995. Unit Lima is at the top, slightly lefthand side of this image, up and left of the circular white dirt road. Note the trees still growing on now exposed Bed Igl.

38 Figure 54 An aerial view from Unit Lima is at the top, slightly lefthand side of this image, up and left of the circular white dirt road. Note the trees still growing on now exposed Bed Igl. The creek course has diverted downhill, settling into its ancient bed. Note, at the left, bottom corner (south of the creek course), the field has been put into cultivation. Directly downhill, ca. 25 in elevation, from the top right hand corner of the cultivated field, is where the furnace and mold are positioned. Apparent are many large trees still rooted into Unit Lima s alluvium, overlying the position of the furnace and mold.

39 Figure 55 Highlighted 1995 aerial view. Unit Lima is at the top, slightly lefthand side of this image, at a ca. 45-degree angle, up and left of the circular white dirt road. Note the trees still growing on now exposed Bed-Igl. The creek course has diverted downhill, settling into its ancient bed. The blue highlighting represents the creeks current bed (and ancient bed). The yellow highlighting represents the prior creek bed, as portrayed in the 1985 aerial shot.

Figure 56 Aerial photo from 2003. There is no indication of large trees remaining on Unit Lima s alluvium. The creek course change is readily apparent.

40 Figure 56 Aerial photo from There is no indication of large trees remaining on Unit Lima s alluvium. The creek course change is readily apparent. Dissection of Unit Lima s alluvium is now readily apparent, with the southern, uphill portion of Bed Igl exposed, and the northern, downhill portion of Bed Igl still covered by the overlying, fine-grained strata. The current creek course is now the ancient Ked creek bed, at the bottom of the valley of downward sloping Ked bedrock, running between the underlying southern Ked and northern Ked valley margins, that parallel the creek bed.

Figure 57 1981 USGS topographic map of Unit Lima. Note there is no indication that Unit Lima s alluvium has been dissected. Only cleared pasture, depicted in white, is evident.

41 Figure USGS topographic map of Unit Lima. Note there is no indication that Unit Lima s alluvium has been dissected. Only cleared pasture, depicted in white, is evident. Figure USGS topographic map of Unit Lima. Note there is no indication that Unit Lima s alluvium has been dissected. Only cleared pasture, depicted in white, is evident. The red highlighting represents the creeks current bed.

42 Figure 59 Dissected Unit Lima, directly above the furnace and mold. Dr. Steve Kissin, Lakehead University, observes the furnace.

Starting at Rock Bottom: A Peculiar Central Texas PreClovis Culture

Starting at Rock Bottom: A Peculiar Central Texas PreClovis Culture Background Brushy Creek grades, overall, west-northwest (WNW) to east-southeast (ESE) through the easternmost portions of the central