EL MIRON CAVE DATE LIST VI
El Mirón Cave (Ramales, Cantabria, Spain) has provided one of the largest series of radiocarbon (14C) dates from any single prehistoric site in Europe, spanning the terminal Middle Paleolithic through the early Bronze Age and even the Medieval period (Straus and González Morales Reference Straus and González Morales2003, Reference Straus and González Morales2007, Reference Straus and González Morales2010, Reference Straus and González Morales2016; Straus et al. Reference Straus, González Morales, Higham, Richards and Talamo2015). Among the results are coherent direct and indirect accelerator mass spectrometry (AMS) dates for the first human burial of Magdalenian age ever found on the Iberian Peninsula. However, many of the other assays done early in the long excavation project were conventional 14C dates and there are several stratigraphic inconsistencies, especially in the vestibule rear (“Corral”) excavation area.
In order to more accurately to determine the beginning and end of the use of this montane cave during the Last Glacial Maximum by humans armed with Solutrean stone points, previously dated by three conventional assays on bone collagen and one AMS assay done on charcoal, samples from a red deer (Cervus elaphus) tibia and from a red deer radius from the base and top of the series of Solutrean layers (Levels 127 and 122 respectively) were sent to the University of Georgia Center for Applied Isotope Studies.
To improve the dating of a rich and particularly interesting Lower Magdalenian occupation—Level 115—also at the rear of the cave vestibule (within the same general culture-stratigraphic period as the nearby human burial known as the “Red Lady of El Mirón Cave [Straus et al. Reference Straus, González Morales, Higham, Richards and Talamo2015]), a red deer long bone shaft splinter was also sent to Georgia. This level, with a possible “wall” formed of both limestone blocks fallen from the cave ceiling and large water-worn cobbles (probably from alluvial fill in the cave interior) (Straus and González Morales Reference Straus and González Morales2018), had previously been dated by a conventional assay (on bulk bone fragments) with a patently unsatisfactory result of 13,800 ± 840 BP—the Upper Paleolithic date from El Mirón with by far the largest standard deviation.
The protocol for bone collagen sample treatment at the Georgia lab includes rigorous filtering to remove extraneous materials (Alexander Cherkinsky, personal communication, 2017). The results of these three assays are presented in Table 1.
AMS 14C dates on bone collagen samples from El Mirón Cave.
* CALIB 7.1.0, used with Stuiver and Reimer (Reference Stuiver and Reimer1993)
Basal Solutrean Level 127 had earlier been dated to 19,230 ± 50 BP on a piece of charcoal—a millennium more recent than the new date, perhaps explainable by downward movement of the small sample. The new date is one of the oldest for the Solutrean in Cantabrian Spain, along with ones from La Riera and Las Caldas caves in Asturias (respectively ca. 120 and 200 km to the west). This is the case despite the fact that it, like the basal Solutrean levels in La Riera and the highest definite Solutrean level in El Mirón (122), contained shouldered (and willow leaf) points—traditionally considered diagnostics of the putative Upper Solutrean (Straus et al. Reference Straus, González Morales, Marín and Iriarte2012). The oldest Solutrean levels in La Riera have repeatedly been dated to ≥20 14C kyr BP (Straus and Clark Reference Straus and Clark1986; Craighead Reference Craighead1999; Soares et al. Reference Soares, Gutiérrez-Zugasti, González Morales, Matos Martins, Cuenca-Solana and Bailey2016), while the basal Solutrean at La Caldas lacks shouldered points, but has a similar date and is called Middle Solutrean (Corchón Reference Corchón2017). There is an undated, thin, discontinuous, but intact level (121) above 122 that is sedimentologically grossly similar (brown-yellowish brown clayey silt, relatively poor in organic matter and with low density of cultural and faunal materials), but lacks Solutrean points. At the top of this level there is a sharp, clearly visible sedimentological unconformity. The overlying Initial (and Lower) Magdalenian levels are dark, blackish-brown, sandy loam and very rich in charcoal, artifacts, faunal remains and fire-cracked rocks. The oldest of these levels (119.2) dates to 17,620 ±40 BP, suggesting the existence of a depositional hiatus between the Solutrean and early Magdalenian levels.
Level 115 is underlain by 116 and 117, whose four oldest dates are in the range of 17–17.4 14C kyr BP (with two presumably anomalous dates of ca. 15.4 14C kyr BP from Level 116). It is overlain by dates of 16.8 and 16.5 14C kyr BP from Level 114, making the new 115 date of 16,750 seem coherent and plausible. These ages fall around the time of the ill-defined transition between the Cantabrian Initial and Lower Magdalenian (González Sainz and Utrilla Reference González Sainz and Utrilla2005).
NEW DATES FOR THE MAGDALENIAN OF LA RIERA CAVE (POSADA DE LLANES, ASTURIAS)
The original (late 1970s) dates for the upper parts of the Magdalenian sequence in La Riera Cave included several inconsistencies (Straus and Clark Reference Straus and Clark1986). In particular, the sole date for Level 24 (which was very rich in osseous tools, notably a bilaterally barbed harpoon fragment) and one of two dates from underlying Level 23 were both surprisingly late (ca. 10.5 14C kyr BP with very large standard deviations) and out of order with dates from the immediately overlying levels; they obviously needed to be checked. A sample of ibex bone from Level 23 and one of red deer bone from Level 24 were provided to the Georgia lab. The results of the new AMS dating of these two levels are presented in Table 2.
AMS 14C dates on bone collagen samples from La Riera Cave.
* CALIB 7.1.0, used with Stuiver and Reimer (Reference Stuiver and Reimer1993).
La Riera Level 23 falls squarely into the age range of the Cantabrian Lower Magdalenian, as do Levels 20–18 below it based on most of the original dates plus one by Craighead (Reference Craighead1999) for Level 18 (15.6 14C kyr BP). All these levels yielded quadrangular-section antler points (some with hints of “tectiform” engraved markings), very characteristic of this period (González Morales Reference González Morales1986). At least part of Level 24, on the other hand, pertains to an early time in the Upper Magdalenian, as attested by the harpoon. Overlying Level 26 was dated on marine shell by Craighead (Reference Craighead1999) to a corrected age of ca. 11.5 14C kyr BP, essentially identical to a corrected shell date he obtained for Level 24, with undifferentiated Level 21/23 similarly dated to 12.8 14C kyr BP—all younger than is indicated by the new Georgia result. The ca. 2 k cal yr gap between Levels 23 and 24 indicated by the new dates would confirm the existence of an erosional hiatus between the Lower and Upper Magdalenian cultural phases in La Riera that had been proposed by H. Laville (Reference Laville1986) based on sedimentological evidence. The Middle Magdalenian is thus missing at La Riera.
Thus the new dates help to confirm the age range for the Cantabrian Solutrean (ca. 20.5–17.5 14C kyr BP), bolster the evidence for significant erosional hiati between the Solutrean and Initial Magdalenian at El Mirón, between the Solutrean and Lower Magdalenian and between the Lower and Upper Magdalenian at La Riera. They support the recognition being given to the discontinuous nature of the sedimentary records of many Cantabrian cave sites, as recently highlighted in the monographs of both El Mirón (Farrand Reference Farrand2012) and Las Caldas (Corchón Reference Corchón2017).
ACKNOWLEDGMENTS
The dates were financed by the Stone Age Research Fund (University of New Mexico Foundation)—Jean and Ray Auel, principal donors. They were expertly and expeditiously run by Alexander Cherkinsky (University of Georgia, Center for Applied Isotope Studies). The collagen from some of the samples was extracted and the analyses of δ13C and δ15N were done by Jennifer Jones, at the time a Marie Curie Research Fellow in the Archeozoology Lab of the Instituto International de Investigaciones Prehistóricas, Universidad de Cantabria. Excavations in El Mirón were co-directed by the authors and those at La Riera by Straus and G. A. Clark.
