Some Thoughts on Sandia Cave

Dear Virginia -

Thanks to Charlie for posting your reply.

You wrote:

What's the disagreement about a hearth? Four large cobbles, if I
remember correctly, arrange in a rough circle, with charcoal in the
center and associated bones and a Sandia point. Were they rough
limestone slabs, such as could fortuitously fall down into a circular
pattern from the roof, or were they stream cobbles? If the latter, how
(and when) did they get there? The cave is now located 100 m above the
modern stream floor. They could not have naturally rolled into the cave
unless the stream was right outside, and that was before many millennia
of erosion and downcutting by that stream to its current level.

First, the number of hearths. Hibben 1941, page 27, has 2 hearths – – ‘Two definite hearths, or fire areas, occurred in the Sandia level, although flecks of charcoal were fairly abundant throughout. Figure 7 shows both of these to be well within the mouth of the cave, as Professor Bryan suggests, there may well have been more in the portions of the cave now eroded away. The first hearth encountered, that at meter 13 (meter 7 according to the survey of the first year of excavation), was a large area of finely divided charred material measuring some 45 centimeters in greatest width by 30 centimeters in depth, and extending in small pockets or lenses down to and partially into the surface of the white clay layer below.’

Second, whether the hearth, or hearths, were hearths at all. On page 29, H&A raise questions about the identification of Hibben’s ‘charcoal’ – ‘Another caveat that must be considered is the possibility that what was thought to be "finely powdered charcoal" (Hibben, 1937) in a hearth may have been a concentration of biogenic manganese oxide related to the ocher layer. As stated earlier black lenses of manganese oxide were observed within laminae of unit C. Such a lens may have occurred on the floor at meter 7. In spite of about 20 years of experience with most aspects of radiocarbon dating, we still encounter natural concentrations of manganese oxides that are difficult if not impossible to distinguish from some forms of carbon without laboratory testing. If the Sandia concentration was manganese oxide and not charcoal then the first Sandia point, anomalous stones, and bovid mandible might have been accidental associations at the base of the loose debris, in which case all that can be said about the age of Sandia artifacts is that they are no older than 14,000 B.P.’

When found the hearth was buried by younger sediment and not open to the
sky. At least one old photo showed overlying breccia, if I remember
correctly. And no, you wouldn't expect to find a neat sequence of
sediment covering the whole site: that's not how nature works. That's
where the geologist comes in. You would trace the breccia above
(younger than) the fire hearth back into the cave, using the lower
contact, which lies on the floor that then existed at the time. If in
the process you find dripstones interbedded in the breccia above the
contact you are tracing, they would be younger than (lie above) that
contact. That is, younger than the fire hearth lying at the contact
between the breccia and the limestone rubble. So the dripstones would
give a minimum age for the fire hearth.

But before the breccias were cemented, rodents had probably burrowed through them and churned them. So the various layers are very difficult to disentangle.

My understanding is there are three layers of dripstone in the cave. Unit D, the first one, lies below the breccia in which the artefacts were found (Unit F), and above Unit C, the limonite ochre layer. The second layer of stalagmite, Unit G, lies above the breccia Unit F. The third layer, Unit I, lies above Unit H (the upper breccia), unit G, and the rest. Unit F lies immediately above Unit C and under Unit G, the Intermediate Dripstone layer.

But at meter 13 H&A's interpretation (page 5, 14, 15, 21, 22) seems to be that it consists mainly of Unit F and the loose debris of the Unit X layer lying right over the limestone residuum, Unit B.

They conclude that the hearth, the Sandia point and bovid mandible must therefore have come from somewhere within Unit F (12,000±400 B.P) (page 29) or Unit X ( 'a general time period of between 11,000 and 14,000 years ago' - page 21).

Can you supply more information about the incorrect 30,000 year date?
If I'm right, the actual date would be "greater than" 30,000 years, the
limit of the C14 dating method at the time.

On page 8, H&A say about Unit G ‘. A radiocarbon analysis of this unit (Table 2) yielded an apparent age in excess of 30,000 years (1-471) but the dating of more reliable materials and the archaeology above and below this unit show the date to be in error.’ They give the RCD for Unit I as 19,100±900 (page 10, Table 2).

40 years ago, Szabo et al (1969, page 241) also had difficulty reconciling uranium series dates with RCD at Valsequillo.

September 3, 2007


Originally posted May 27, 2006

What Frank and Marie Said

Both Frank Hibben and H. Marie Wormington have made comments in past years about Sandia Cave and the types of artifacts found there; Hibben in a letter to me written June 28, 1995, shortly before he died, and Marie in the first edition of her popular book, Ancient Man in North America (1957, Denver Museum of Natural History, Popular Series No. 4, 322 pp.). It would be interesting to see if Marie was as candid in the editions of her book published after 1969, when the U-series dates for Hueyatlaco and El Horno were in print!

Hibben:

. . . Your point is well taken [in a letter to The New Yorker, never published] and Sandia Cave indeed does lie high above the valley floor. We have also found Sandia points, although not a great many of them, at other sites in this area. We have only judged these to be Sandia points if the circumstances surrounding them indicate a Pleistocene date.

. . . The article in the New Yorker failed to mention (although I told Mr. Preston) that Professor Kirk Bryan, at the time Head of the Department of Geology at Harvard University and Professor Kirtley F. Mather, also of Harvard, worked at Sandia Cave. Dr. Mather also helped us with the geology at another site at Comanche Springs, south of Albuquerque, which also contained a few Sandia points.

Anybody ever hear of the Comanche Springs site?

There is a site called Comanche Springs Cave - http://www.caver.net/coma1.html - but that's 500 miles from Albuquerque.

There's a place called Comanche Pass - http://philmontdocs.watchu.org/Docs/Pro ... e_1957.pdf - which is much nearer Albuquerque. (Comanche Peak and Comanche Pass are mentioned here - http://www.troop111.org/philmont-2000/day12.html). There's a plan of Comanche Pass here on page 34 (and note 4) - http://philmontdocs.watchu.org/Docs/Iti ... s_1972.pdf - and a description here - http://www.brainygeography.com/features ... epass.html.

Hi Ellis.

Virginia asked me to post this reply for her:

Dear Ellis,

Have been busy with the Pleistocene Coalition News newsletter
( http://pleistocenecoalition.com , then click on newsletter box at the
left of the home page for latest issue; scroll down to the bottom of the
home page for past issues) and have not had a chance to check my website
for many weeks. Sorry to again leave you hanging.

I'll also be away from the computer for awhile beginning next week, so
again, my responses may be delayed.

In a recent post, you wrote, "40 years ago, Szabo et al. (1969, page
241) also had difficulty reconciling uranium series dates with RCD at
Valsequillo." Where did you read that? Szabo mentioned a difference
between RCD and U-series dates for the Colorado Lindenmeier site
(U-series dates too young). By contrast, if you look at Table 2 on page
241, the U-series dates for a proboscidean vertebra collected from the
middle part of the sediment sequence exposed in the Caulapan barranca (a
steep-walled, flat-floored gully located a few km. to the northeast of
Hueyatlaco), you see that the U-series dates for the bone and the RCD
for associated molluscan fossils are very close, roughly 22kya. No 14C
dates for the U-series-dated bone associated with artifacts at the
Valsequillo sites (Hueyatlaco, El Horno) because "no datable carbon
remained" (Of course not! The sites are way too old to be dated by the
14C method.)

Dear Virginia,

In a recent post, you wrote, "40 years ago, Szabo et al. (1969, page
241) also had difficulty reconciling uranium series dates with RCD at
Valsequillo." Where did you read that? Szabo mentioned a difference
between RCD and U-series dates for the Colorado Lindenmeier site
(U-series dates too young). By contrast, if you look at Table 2 on page
241, the U-series dates for a proboscidean vertebra collected from the
middle part of the sediment sequence exposed in the Caulapan barranca (a
steep-walled, flat-floored gully located a few km. to the northeast of
Hueyatlaco), you see that the U-series dates for the bone and the RCD
for associated molluscan fossils are very close, roughly 22kya. No 14C
dates for the U-series-dated bone associated with artifacts at the
Valsequillo sites (Hueyatlaco, El Horno) because "no datable carbon
remained" (Of course not! The sites are way too old to be dated by the
14C method.)

(Thanks again to Charlie for posting your reply).

Maybe I should have written '237' not '241', sorry. The title of the paper is 'Dilemma posed by uranium series dates on archaeologically significant bones from Valsequillo'. And on page 243, Szabo et al say how 'perplexed' they were by the discrepancy between the RCD and uranium-series dating results.

You say 'the Caulapan barranca (a steep-walled, flat-floored gully located a few km. to the northeast of Hueyatlaco), you see that the U-series dates for the bone and the RCD for associated molluscan fossils are very close, roughly 22kya.'

On page 240 Szabo et al agree with this point at least as regards sample MB6. As regards MB5, concerns over its provenance could be the reason for the discrepancy (roughly 12,000 years) between the RCD and uranium series dates. (But the gap in the MB4 (horse metapodial from Atepitzingo) dates was very wide - 340,000± 100,000 Th as opposed to 35,000 RCD.)

You say 'No 14C dates for the U-series-dated bone associated with artifacts at the Valsequillo sites (Hueyatlaco, El Horno) because "no datable carbon
remained" (Of course not! The sites are way too old to be dated by the 14C method.)'

But this statement seems to be based on the assumption that the sites must be very old, and doesn't appear to take into account the unreliability of Uranium Series dating. If there were dating discrepancies at only one site, there might be a case for arguing that some uranium series dates must be right. But there are discrepancies between the different dating methods at Valsequillo, and also comparable discrepancies between the different dating methods at Sandia Cave. So surely it could only be safe to make your statement if Uranium Series dating had been shown to give pretty much the same results as RCD in most cases - which it doesn't - and/or if there was other corroborative evidence confirming the supposed antiquity of the sites - which there isn't.

Hello, Ellis, Virginia sent this for me to post here on her behalf. She is still having problems logging in here.

Dear Ellis,

So what's a two-month-plus delay in my reply? Sigh.

I am a volunteer copy editor for the Pleistocene Coalition News newsletter (<http://pleistocenecoalition.com/>, then click on the box to the left at near the top of the home page for the latest issue; scroll down to near the bottom for earlier issues.) It's taken up essentially all my computer time. Hopefully the load will lighten as I continue to learn the ropes.

Comments on your June 3 post:

1. The Szabo et al paper did NOT say they were "perplexed" by the discrepancy between RCD and U-series dating results: they were perplexed why "some of these dates are much older than expected from the archaeological evidence." It was data vs dogma, couched for publication in the most polite terms possible, considering the strength of feelings involved.

Remember, when U-series dates were found to be in disagreement with RCD, the U-series dates were too YOUNG (example, the L-B-1 bison astragalus from the Lindenmeier site, Colorado.)

2. As for the Atepitzingo horse metapodial, the RCD date wasn't 35,000 years, it was GREATER THAN 35,000 years, which takes in the Pre-Cambrian! See the current May-June issue of the PCN newsletter, pp. 10-11, 16-17 for more on Atepitzingo.

3. We are not "assuming" the Hueyatlaco site is very old; we presented hard evidence back in the 1981 Quaternary Research paper and continue to do so. See the March-April issue of the PCN newsletter pp. 1-3 and cited references for Sam VanLandingham's latest on the diatoms. There's your "corroborative evidence" which you say doesn't exist.

U-series dating methods are used routinely in Africa; I don't think the folks there think they are unreliable. And remember that Szabo had a series of internal checks on his dates (see his Table 2 for the various ratios.)

Virginia