James Lane here noticed a couple of other useful references on Quelccaya and related the anecdotal information to this information. He observed:
It took me ages to put this post together, juggling between different sites. I don’t think one can conclude anything from the information, as presented, except that the moss has grown at higher altitudes in the past than now.
His location is a substantial improvement over what I’d posted up before, about which Lee complained. I’ll take another crack at collating the information in light of James’ additional thoughts on the matter.
First, James points out that the "glacier" and "ice cap" do not seem to have a fixed usage in many reports, but that a useful distinction does appear to exist. Here’s a differentiation according to Goodman et al 2001 (cited by James):
Whereas glaciers in the CV have receded into alpine cirques (Fig. 2), the QIC is surrounded by short, steep outlet glaciers up to »2 km long. The QIC covers 70 km2, reaches 5645 m in elevation, and is the largest tropical ice cap in the world (Mercer and Palacios, 1977) (Fig. 3).
I’ll try to follow this usage and limit "glacier" to the "short, steep outlet glaciers". Here once again is the location map from Mark et al (there’s also a useful map in Goodman et al 2001, which can be collated to this map. When we read about the receding Quelccaya glacier, I think that this is generally the outlet glacier in the Huancane valley marked in on this map. There is also evidence of outlet glaciers in other valleys in the past, which are no longer there, but which have left moraines, that are discussed in Mark et al and Goodman et al.
Figure 1. Mark et al 2002 FIG. 2. Map of the study area in two parts: … (b) the Huancane Valley, Quelccaya Ice Cap. Moraines and the numbered sample sites for radiometric dates (coinciding with Table 1) are shown. Also presented are the modeled paleoglaciers, overlaid on the topography of the digital elevation model (shown by contour lines).
Here is a USGS map showing topography a little more clearly/
Samples Discussed in Mart et al and Goodman et al
Starting at the north, Mark et al report a result from Mercer and Palacios 1977 (MP77) marked as location 14 (altitude 5100 m) in the above map that is the "upper peat beneath an H1 terminal moraine". Thus there was an outlet glacier in this valley which has now receded back to the ice cap. It was dated BP 270 C14; 300 calibrated and was a basis for assigning an LIA date to H1 moraines. While the H1 moraine is shown in the map in the Huancane valley, it is presumably dated by cross-dated stratigraphy as no C14 date for this particular moraine in the Huancane valley is shown.
Location 10 (4820 m) in the Huancane valley is the H2 terminal moraine. The upper peat beneath the H2 terminal moraine is dated 10910 C14; 12830 calibrated. Pit Q4 is at this location. One of the samples is said to be "Peat and rootlets incorporated into till of Huancare 2 moraine". Another sample at this location (reported in Goodman et al ) is 10170 C14; 11890 calibrated.
Goodman et al report four samples associated with site 13 (altitude 5180 m), all of which are upvalley from Laguna Paco Cocha "modern ice margin above Laguna Paco Cocha" (not all of which are reported in Mark et al 2002). There appears to be an outlet glacier in this valley as well. The samples are said to come from a "time when QIC was smaller than present" – although it remains unclear whether "present" in this context means 1977 or 1997 (when the more recent geological visit took place.) The oldest sample, said to be "basal peat beneath modern glacier" was dated 2670 – C14; 2760 calibrated. A second sample, "upper peat beneath modern glacier" was dated 1950 C14; 1880 calibrated. A third sample, "upper peat beneath modern glacier" was dated 1625 C14; 1520 calibrated. A fourth sample, "upper peat beneath modern glacier" was dated 1395 C14; 1290 calibrated. In all cases, the table states that the the peat was created at a "time when QIC was smaller than presen".
Location 12 appears to be in the next valley to the south of the Laguna Paco Cocha valley. Goodman et al: "the youngest moraines, on which soil pits Q5 and Q6 were dug, are found 100–200 m from the ice margin." "These small ridges are composed of mostly fresh, ignimbrite cobbles and reveal little pedogenic development. Their stratigraphic position upvalley from the Huancane I moraines, which were dated at <270 § 80 14C yr B.P. (300 cal yr B.P.) by Mercer and Palacios (1977), indicates that these moraines also formed within the last several centuries, coincident with the Little Ice Age". Pits Q5 and Q6 (said to be at 5070 m in Mark et al; 5100 m in G01) reported two samples. The oldest sample, of "basal peat incorporated in Huancane I moraine (maximum age for Huancane I moraines and soils Q5 and Q6)" dated 905 C14; 790 calibrated. The younger sample, of "uppermost peat incorporated in Huancane I moraine" was dated 279 C14; 300 calibrated maximum age.
It’s hard work assigning Thompson’s samples to this map, but I think that James’ detective work has more or less located them. Here are two quotes that need to be coordinated:
"This year , the researchers found a second plant near the southern tip of the ice field, some 6 kilometers (3.7 miles) south of their original plant find. Thompson believes that this second plant may provide important historical information about this site. Subsequent carbon dating of the second plant showed that it had been buried for the last 2,200 years, a time when other records showed another abrupt climate change."
A second quote is:
This time , Thompson decided to look up a different valley, some 1.8 miles (3 kilometers) from the initial plant find. “But about a quarter-mile from there, I found yet another area of uncovered plants.”
"2) This places the 2200 BP sample well away from any of the sites on the Mark map (although the southern extremity is depicted in the map). This sample would appear to be from between 5000-5200 metres."
3) The above would appear to give us an indication of the location of the 5200 BP sample – i.e. 6 km north. This would place it near site 14 (the 270 BP sample), although whether it is above or below the terminal moraine is unclear. In the context of Thompson’s conclusions, one would have to think it was above the moraine.
4) The location of the 50,000+ BP sample is a mystery. The press report suggests that Thompson intended to look in a different valley 3km away (maybe somewhere near site 8 on the Mark map – BTW this is labled in Table 1 as “beneath H2 terminal moraine” WTF?). But it’s then reported that he found it closer: “But about a quarter-mile from there, I found yet another area of uncovered plants.” This site is reported as being at 5000m, which would make it lower than the 2670 BP site, at 5180 metres.
My take on this is that the 2003 plant deposit (2200 years old) was found in an outlet valley one valley to the south of the Location 12 valley where pits Q5 and Q6 were dug. I think that the above information suggests that the 2004 plant deposits (50,000 years old and 5000-6000 years old) might have been found in the Laguna Paco Cocha valley or in the location 14 valley if to the north, while the original 2002 discovery might be in the Huancane valley itself. All the samples appear to be associated with past and present outlet glaciers as opposed to the "ice cap" in the narrow sense.
Obviously this is speculative. Why the hell wouldn’t Thompson have included something as routine as a map showing the locations of the samples.
Here’s a picture of the 2003 plant deposit:
Caption: As the margin of the Quelccaya Ice Cap receded over the past year, it revealed a second large plant deposit that had originally been buried by the advancing glacier. At left, the plants with a field notebook (yellow) for scale. Carbon dating places the plant’s age at 2,200 years before present.
Here is a picture of the 2004 area of 50000 year old peat:
Original Caption: A team member gathers samples of plant material recently uncovered as the glacier’s margin retreated. Carbon-dating provided an age for the plants of at least 50,000 years.
Here’s a picture of the 2006 area of 4-6000 year old peat:
Caption: Above, OSU glaciologist Lonnie Thompson and University of Texas botanist Blanca Leon examine deposit of ancient alpaca moss recently exposed by the retreat of the Quelccaya ice cap in the Peruvian Andes. The deposit was covered some 5,200 years ago as the ice cap expanded. Recent warm periods in the region uncovered large mats of the moss.
Adam Y. Goodman, Donald T. Rodbell and Geoffrey O. Seltzer and Bryan G. Mark, Subdivision of Glacial Deposits in Southeastern Peru Basedon Pedogenic Development and Radiometric Ages
Mercer, J. H. (1984). Late Cainozoic Paleoclimates of the Southern Hemisphere South of the Equator. In “Late Cenozoic Paleoclimates of the Southern Hemisphere” (J. C. Vogel, Ed.), pp. 45–58. Balkema, Rotterdam.Mercer, J. H., and Palacios, O. (1977). Radiocarbon dating of the last glaciation in Peru. Geology 5, 600–604.
Here is a map from Goodman et al, together with a slight zoom of the same map.