Radiocarbon Samples and Archaeological Excavation: a Commentary Based on the "Valdivia Absolute Chronology"
Universidad Autónoma de Barcelona Departemento de Geologia, Edificio CS 08193 Bellaterra Barcelona, España. |
Gliwice Radiocarbon Laboratory Institute of Physics Silesian Technical University ul. Krzywoustego 2 44-100 Gliwice, Poland. |
Summary
The cultural chronology of Ecuador is based on several hundreds radiocarbon determinations. Most of the dated samples, which come from coastal sites, are charcoal, however a good number were shell and few were the collagen of human bone. Some dates were obtained by other methods. Early in the fifties, obsidian hydration dates served to complete the 14C sequence, and more recent Thermoluminescence assays have not only completed some missing dates for a more refined sequence, but have served to validate some 14C calibrations and to explain some aberrant determinations. In the following commentary, we will refer mostly to Valdivia dates, since they were obtained by the most varied field methods, during the forty years Valdivia sites have been under excavation.
This paper has two parts: firstly, an archaeological discussion of the Valdivia absolute chronology by Jorge Marcos; and secondly, the presentation of the calibration of the Valdivia dates in the Gliwice Radiocarbon Laboratory, by Adam Michczynski. Marcos, discusses the importance of selecting a 14C sample in order to obtain a secure date, and the most common errors that have affected the Valdivia absolute chronology. The necessity to calibrate dates, and the importance of publishing them properly. (1)
The results of calibration of individual 14C dates by Adam Michczynski are presented in Table 1 and Figure 1. Finally, as a corollary, a commentary on the problems presented in the combined presentations is provided by the senior author.
Introduction
When Willard Libby published the first radiocarbon age determinations in 1949, a rapid growing and widely accepted impression, that at last a direct scientific procedure to determine absolute chronologies had been discovered, invaded the archaeological discipline. Most archaeologists became “true believers” of the “Radiocarbon Revolution”, and it took nearly thirty years before the discipline accepted a different reality.
We know now that radiocarbon determinations can not be translated into BC/AD calendar years by the simple addition or subtraction of 1950 years. We also know of the existence of an effect, which not only registers different atmospheric concentrations of 14C for different periods, causing determinations not always to agree with real dates; but it can also happen that one particular radiocarbon determination may represent more than one true date.
Libby, had assumed that 14C atmospheric concentrations had been constant in the past; but now we know that it was variable, and that this was mainly due to changes in the earth magnetic field. Dendrochronology, the method that demonstrated 14C dating inexactitudes, also provided us with a way to correct, calibrate and thus to convert 14C assays into real calendar years. Since then, several methods for correction and calibration of radiocarbon assays have been offered, the most recent by Stuiver, Long and Kra (1993). Recently, the methodological advance experimented in radiometric analysis has been enormous. These advances not only refer to 14C dates calibration, and statistical correction of radiocarbon assays, but also to the development of more precise ways to treat the organic samples and to determine the concentration of 14C, like the introduction of the accelerator mass spectrometer (AMS), which allows the direct measurement of smaller samples. This has been called the “second radiocarbon revolution.”
The “Radiocarbon Revolution”
As a result of this conception of the “Radiocarbon Revolution”, up to 1974, all organic samples used for 14C determinations of the Valdivia chronology in coastal Ecuador were gathered by “artificial” metric levels of excavation (Meggers, Evans and Estrada 1965: 15-21, 147-156). A good number of these samples were sea and estuarine shells, while a lesser number corresponded to wood charcoal samples. Most of the metric levels used, were 30 cm. thick taken from 5 x 5 m. units. This “artificial stratigraphy” disregarded visible cultural deposits and intrusions, like erosion channels, hearths, postmolds, storage pits, etc., as Bischof and Viteri noted in 1972.
During this period, in Ecuador (like in most of Latin America) not only the majority of 14C determinations came from excavations such as this, but a good number of them were published without their laboratory reference number. Even today, this convention is hardly followed, as well as the unconventional practice of publishing uncalibrated dates followed by B.C. and A.D, and not in lower case, as it should be, misleading readers, and making of any chronological comparison a deceitful effort.
As an example of the problems introduced in the past, and in some present cases, the Valdivia cultural is especially valuable. Bischof and Viteri (op.cit.) not only demonstrated a that at the type site (G-31) 14C assays were discordant with their purportedly stratigraphic position, but showed that clear stratigraphic deposits, that could have allowed to precisely define the depositional history of the site, were ignored. The problems with the generalised “artificial stratigraphic” method of excavation used then, became more apparent during the early months of excavation at Real Alto.
In 1974, NSF awarded the Illinois archaeological team, headed by D. W. Lathrap, funds for the excavation of Real Alto. The major literature on Valdivia, at that time, indicated that such sites did not allow to clearly determine stratigraphic deposits. Most reviewers of the project considered that the Midwestern, Mississippian Bottom-Lands, excavation procedure, proposed by the Illinois team of archaeologists was not applicable to the excavation of Real Alto. As a result, the grant contract provided a restriction on the excavation procedure, it forced us to excavate the site by metric levels. Since we were convinced that we would be able to identify different soil deposits, as well as cultural features such as wall-trenches, house-floors, food-preparation, ovens and storage pits, a compromise was reached. We were allowed to excavate in alternate units. Even numbered units were excavated removing cultural deposits in the way done by most Mississippian archaeologists, as we had planned, and in the odd numbered units we had to use the artificial metric-level method, imposed by the grant.
We had only to excavate metrically five odd units before it became obvious that such method was destroying important retrievable information, and it was dropped. We found out that after excavating thirty centimetres, removing all deposits and intrusive fills, only about 30% to 40% of the next 10 cm. layer remained to be excavated. From then, a 60% to 70% intrusions remained as a constant throughout the sequence, even below 120 cm. deep where the undisturbed geological strata began to emerge. Meaning, that if we had followed the traditional method of excavation and ceramic type serration used in Ecuador during the fifties and early sixties, we would have been treating as contemporaneous, materials with a with only 30% to 40% probability, with an added 360 to 480 years margin of error beyond that implied by the 14C method itself (see Appendix 3).
Sampling for Radiocarbon dates
Thus the first Valdivia “dates”, from samples taken in the late fifties, served to confirm the antiquity of that phase in Coastal Ecuador. And although, such samples dated also some Late Formative, Regional Developmental and Integration Period episodes. Valdivia, being the better dated and studied Early Formative Culture in Coastal Ecuador, allows for a more detailed commentary on the 14C dating problems.
The 14C determinations from the type-site (G-31), and from other Valdivia sites excavated by Meggers, Evans and Estrada (op. cit.) in the fifties, due to the excavation strategy used, which disregarded contexts, could only roughly date the grossly estimated four sub-phases proposed by these authors.
In the early sixties a Columbia University team of archaeologists, headed by Edward Lanning (1964), surveyed the Santa Elena Peninsula, and surface collected ceramic samples from several thinly occupied sites, defining the late preceramic Vegas occupation. This exploration of the Santa Elena Peninsula sites allowed Betsy Hill to refine the Valdivia sequence into eight phases. Alison Paulsen, did likewise with Guangala for which she identified nine phases, and three for the Integration Period occupation, which had been defined as Manteño by Bushnell, and she now called Libertad. During the late sixties, Henning Bischof (1972) refined the Engoroy and Machalilla (2) sequences obtaining a good number of 14C dates which included some for early Guangala.
In the seventies, Presley Norton and Felipe Cruz excavated the Loma Alta site 19 km. inland, deep into the Valdivia river valley. They improved on the excavation procedure used up to then, by being able to separate an Engoroy level covering two Valdivia occupations. With the aid of B. Hill, Norton (1972) identified the deeper cultural deposits as Valdivia phases 1 and 2. However, the greyish dusty midden did not allow them to identified some features, like Valdivia 2 storage pits, whose contents were interpreted as ’cairns’. The several wood charcoal samples obtained correspond nicely with such phases, with the exception of those gathered from the ’cairns’, which date to Valdivia phase 2.
Proper Excavation, the validation of 14C and TL determinations.
The quality of excavation reflects on the validity of the increasingly more precise physical methods of chronological determination. The earlier Valdivia dates, which samples were obtained form metric levels served to date periods, but not events. Today, the appropriate selection of the sample is of great importance to validate closed contexts and micro-stratigraphic relationships. Ideally, we should date no less than five 14C samples per event, to select against on-site and laboratory contamination and error. However, the availability of organic material, and cost, are a constrain. This can be offset by the use of less expensive comparative methods, like TL chronological determinations. We have done so successfully at Real Alto, Punta Tintina, Loma de Los Villones, and San Lorenzo del Mate (3) (see Appendix 2).
Excavations at Real Alto
Research at Real Alto began with a non random surface collection by the senior author (Marcos, 1978, 1988). This collection was analysed during 1972 and 1973 to plan an excavation strategy for the 1974/75 excavations at Real Alto. In the process of analysing material samples a lump of ’terracotta’ with two textile imprints was discovered (Marcos, 1974). The associated material were Valdivia phase 7 sherds. To compare this event with other cotton textile bearing contexts from coastal Peru, a preliminary attempt at correction for isotopic fractionation of 14C shell determination and an statistical calibration for existing Valdivia determinations were attempted by Gary Vescellius (ibidem) (4).
Since 1974, during excavations at Real Alto, a more refined method of excavation was introduced, for the first time, to a Formative site in coastal Ecuador. House floors and public building floors, were identified and excavated, together with associated burials, hearths, food preparation pits, ritual paraphernalia disposal pits, and bell-shape storage pits, etc. Samples for 14C determinations were obtained from these closed contexts, and their stratigraphic correlation was verified. Although some 14C determinations correlated nicely with microstratigraphic deposits, others obtained from wall-trenches and from food-preparation pits, appeared not to correlate with the stratigraphic sequence. However, once calibrated, some of these dates became acceptable, but others were simply wrong.
Excavations conducted since the mid eighties at Real Alto and San Lorenzo del Mate have shown some site formation peculiarities, and have permitted refined observations of the manner of building and rebuilding public edifices and households, which could explain some of the chronological aberrations.
• All Valdivia buildings were placed on top of a prepared platform mound, which were reworked and reshaped when a major rebuilding of the structure took place. This became more obvious at San Lorenzo del Mate where the limonite-rich soils clearly showed the forming of house platforms throughout the stratigraphy. This is also evident in Real Alto deposits, clearly showing in Mound A (Marcos, 1988).
• In most of the wall-trenches it was evident that wall posts were removed and replaced from time to time.
• Surface hearths similar to those found ethnographically among Amazonian groups are common in Valdivia house floors, as well as bell-shaped food preparation pits (see Zeidler, 1984:327, Map 49; Marcos 1988:48).
• Bell-shape storage pits generally contained manos and metates, or rests of them. These sacrificial rites filled to capacity some storage-pits with broken manos and metates (Marcos, 1978; 1988:144-145).
Building activity, could explain some wood charcoal sample up-mix, especially in wall trenches. But well defined bell-shaped food-preparation pits should contain only charcoal from the cooking activity performed there, and aberrant dates could not be explained by up-mixture. On the other hand, re-use and replacement of wall-posts activity, could indicate that a good percentage of the wood burnt in hearths and oven-pits were old, discarded, building material. Long-lasting wood, like algarrobo and guasango, would date to several centuries before, when the tree was cut, and not when it ended as fuel.
Our recent excavations on the north-east sector of Real Alto, have shown that the so-called cairns found at the bottom of the excavation in that sector of the site, are actually the bottom of, Valdivia 2b, bell-shape storage-pits where manos and metates where stored, or sacrificed before filling the pit with rubble (5). This is coherent with some of the dates associated with cairns, which date to Valdivia 2b and not to Valdivia 1a.
Calibration of Radiocarbon Dates from Valdivia Culture
The results of calibration of individual dates are presented in Appendix 2, Table 1 and Figure 1. All dates were calibrated using the Gliwice Calibration Program GdCALIB (Pazdur & Michczynska 1989). The calibration curves used for the calculation were taken from Radiocarbon - Calibration 1993 (Stuiver, Long and Kra, 1993). Due to irregular multimodal shapes of probability distributions of the major part of these dates it was decided to present the results in a form of 95% confidence intervals of the highest probability (narrowest 95% confidence intervals) - the same form, which was used in ANDES catalogue (Ziólkowski et. al. 1994). The intervals presented in Table 1 were rounded to 5 years and corrected (after analysis of the shape of probability distribution of calendar age obtained for each date) in order to remove unimportant information. There are some dates with 95% confidence intervals divided into two or three parts. For these dates the probability of each part of interval is placed in brackets. Especially, dates SI-81 (Valdivia) and ISGS-446 (Real Alto) give after calibration two clearly separated parts with equal probability.
The obtained results agree very good with appropriate TL dates. For almost all radiocarbon dates TL date is inside 95% confidence interval of calibrated radiocarbon age. Only three dates from San Isidro (Valdivia Phase 8) are exceptional, but even for them the 95% confidence intervals of calibrated radiocarbon age and ±1s intervals (intervals of standard error) of TL dates are abutting.
The results of calibration of selected dates related to succeeding phases are presented in Figures 2. Table 2 contains a list of dates included in the calibration. Its important to accent that the number of dates included to analysis is not enough for delimitation of time intervals of individual phases with high reliability, but it is sufficient for approximate estimation.
Figure 2 shows composite probability distributions of calibrated radiocarbon dates for succeeding phases of Valdivia obtained from sites Real Alto, Loma Alta, Colimes, Ayalán and San Isidro (see Table 2). We can note, that chronological succession is evident, although the distribution is partially overlapping. All distributions (Except phase 1a) have a shape with the highest part in the middle. We can assume, that limits of these middle parts show presumable limits of appropriate phases.
The time intervals of individual phases specified as 50%, 68% and 95% confidence intervals of appropriate composite probability distribution are presented in table 3. It is not straightforward task to decide, which of these intervals is the best image of time interval of specified phase. We suggest to use the 68% confidence interval, which corresponds ±1s interval of radiocarbon dates, or 50% confidence interval, which conform to conception of the floruit of a culture, proposed by Barbara Ottaway (Ottaway, 1973; Atchinson et. al., 1991).
Concluding Remarks
Early use of 14C dating in Ecuadorian archaeology, was undoubtedly of great importance to substantiate the antiquity of the Formative process there. The method of excavation employed, which disregarded the history of site formation and its cultural deposits, did not allow for a precise dating of archaeological events. Unfortunately, this has been a widely used method of excavation not only in Ecuadorian, but in South American Archaeology in general. In the middle seventies, although new methods of excavation began to be used, the high cost of 14C assays, did not allow for a sufficient number of organic samples to be dated, and in this way, validate the results of the more precise, forms of event-oriented excavations now in use. The chronic lack of sufficient-funds, since the nineteen eighties, made new advances in 14C, like dating (like AMS) unavailable to most archaeological projects in Ecuadorian archaeology. Many of the few dates obtained are based on any available samples, without selecting them for the least possible form of intrinsic error. Charcoal samples are best, when they come from closed contexts like shards sealed in refuse pits, grains or straw inside adobe bricks, or bits of charcoal in the bake clay of burnt wattle-and-daub walls, or from bone covered with stones or inside a vessel. It is important to be sure that samples had a short life, and that they were not too old at the time they were buried. For this reason such samples like small branches, twigs of brushwood, charred cereal grains, are best. Large charcoal samples, although they appear to give “good dates” to most archaeologists, could “derive from roof timbers -posts or other large pieces of construction material (6) - that might themselves have been centuries old when destroyed by fire, then one is dating some early construction, not the context of destruction.” (Renfrew and Bahn, 1991:126-127).
It is important for archaeologists not only to be aware of the various forms of contamination a sample might have been subjected to, in the past (7). They should also make sure, themselves and their action in the field and in the laboratory are not a major source of contamination (8). The assays, and the calibration should be discussed critically with the physicists at the 14C laboratory in order to obtain a good date for the event. It has been mentioned above that the best way to secure a valid sequence of dates, is to date at least five samples from each clearly-stratified context that needs to be dated. However, because it is difficult to obtain sufficient datable organic materials at most sites, other dating methods such as thermoluminescence of potsherds should be undertook. Yet, because we are dealing with methods, it is not a straightforward procedure. It is necessary to compare, both 14C and TL dates with respect to the relative rate of deposition apparent in the site stratigraphy. This has been done for the Valdivia sequence based on the 14C calibrated dates for Real Alto and Loma Alta, and on the TL dates for Real Alto, Punta Tintina, Loma de los Villones, San Lorenzo del Mate, in relation to the stratigraphic deposits in Real Alto, and San Lorenzo del Mate. Ceramic modal-analysis and the study of changes in paste composition and firing temperature (9), have also served to refine the ceramic phase indicators proposed by Betsy Hill (1972/1974), which have served to substantiate the ceramic phases presented in Table 4.
There are enough radiocarbon dates for all Phases of the Valdivia chronological sequence (see Marcos, 1988 (1):78-81). However, these were measured before Hill’s (op.cit.) refinement of the sequence into 8 phases, were taken from artificial stratigraphical contexts, and refer to the A, B, and C sequence initially setup by Meggers, Evans and Estrada (op.cit.). The few assays that exist, taken from Valdivia Phases 4, 5, 6 and 7 deposits, present various problems, and therefore were not taken into consideration. Acceptable dates for these phases were provided by direct TL measurement of diagnostic ceramic shards from closed contexts at Real Alto. A dating 14C program of the complete Valdivia sequence, using the most modern methods is hereto a pending assignment.
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calibration of set of unrelated radiocarbon dates | ||||
|---|---|---|---|---|
| No | BP |
[calendar year BC] |
||
| VALDIVIA PHASE 1 | ||||
| 1 | Real Alto | GX-5269 | 6195±215 | 5520-4610 |
| 2 | Loma Alta | GX-7704 | 5275±175 | 4455-3710 |
| 3 | Real Alto | ISGS-448 | 5260±256 | 5065-3940 |
| 4 | Real Alto | GX-5267 | 5495±200 | 4785-3940 |
| 5 | Valdivia | M-1320 | 5150±150 | 4260-3655 |
| 6 | Loma Alta | I-7076 | 5010±120 | 4045-3615 (91%) 3595-3520 (4%) |
| 7 | Loma Alta | ISGS-142 | 5000±190 | 4240-3360 |
| 8 | Loma Alta | I-7075 | 4920±120 | 3965-3500 (92%) 3425-3380 (3%) |
| 9 | Real Alto | GX-5268 | 4900±170 | 4045-3310 |
| 10 | P.Concep. | L-1042D | 4700±100 | 3695-3295 (87%) 3240-3105 (8%) |
| 11 | Real Alto | ISGS-452 | 4700±300 | 4050-2615 |
| 12 | Valdivia | ISGS-275 | 4700±75 | 3650-3335 |
| 13 | Valdivia | ISGS-274 | 4680±75 | 3640-3315 (92%) 3225-3190 (2%) |
| 14 | Valdivia | HV-4674 | 4510±95 | 3500-3455 (3%) 3380-2915 (92%) |
| 15 | Valdivia | HV-4840 | 4495±100 | 3500-3455 (3%) 3380-2910 (92%) |
| 16 | Valdivia | M-1322 | 4620±140 | 3645-2925 |
| 17 | P.Concep. | I-7167 | 4460±90 | 3355-2915 |
| 18 | P.Concep. | L-1042C | 4450±100 | 3365-2890 |
| 19 | Valdivia | SI-84 | 4540±150 | 3630-2895 |
| 20 | Valdivia | SI-83 | 4530±55 | 3370-3040 |
| VALDIVIA PHASE 2 | ||||
| 21 | Real Alto | ISGS-468 | 4760±75 | 3665-3365 |
| 22 | Loma Alta | ISGS-146 | 4750±120 | 3785-3295 (89%) 3235-3105 (6%) |
| 23 | Real Alto | ISGS-452 | 4700±300 | 4050-2615 |
| 24 | Loma Alta | GX-7699 | 4630±160 | 3695-2920 |
| 25 | Loma Alta | ISGS-192 | 4590±120 | 3630-3020 (91%) 2985-2930 (4%) |
| 26 | Colimes | ISGS-477 | 4525±75 | 3495-3465 (2%) 3375-3020 (88%) 2990-2925 (5%) |
| 27 | Colimes | ISGS-478a | 4510±100 | 3500-3430 (5%) 3380-2915 (90%) |
| 28 | Colimes | ISGS-478b | 4460±100 | 3370-2890 |
| 29 | Real Alto | GX-5266 | 4495±160 | 3635-2870 |
| 30 | Valdivia | M-1317 | 4480±140 | 3535-2870 |
| 31 | Loma Alta | HV-4673 | 4335±100 | 3335-2855 (80%) 2820-2665 (15%) |
| 32 | Valdivia | SI-22 | 4450±90 | 3350-2910 |
| 33 | Valdivia | W-631 | 4450±200 | 3635-2610 |
| 34 | El Encanto | SI-1311 | 4405±90 | 3340-2885 |
| 35 | Real Alto | ISGS-466 | 4390±75 | 3330-3155 (20%) 3135-2885 (75%) |
| 36 | Valdivia | HV-4838 | 4260±100 | 3100-2565 |
| 37 | El Encanto | SI-1184 | 4370±85 | 3335-2875 |
| 38 | Loma Alta | SI-1055 | 4370±65 | 3305-3230 (8%) 3120-2875 (86%) |
| 39 | Colimes | GX-5271 | 4365±245 | 3645-2390 |
| 40 | Valdivia | SI-81 | 4270±60 | 3030-2855 (53%) 2820-2660 (45%) |
| 41 | Real Alto | ISGS-446 | 4265±75 | 3035-2835 (47%) 2825-2620 (48%) |
| 42 | Real Alto | ISGS-439 | 4110±75 | 2875-2490 |
| 43 | Loma Alta | ISGS-190 | 3765±85 | 2450-1950 |
| VALDIVIA PHASE 3 | ||||
| 44 | Valdivia | SI-18 | 4230±100 | 3085-2560 (93%) 2530-2500 (2%) |
| 45 | Valdivia | HV-4675 | 4075±110 | 2890-2325 |
| 46 | Valdivia | W-632 | 4190±200 | 3345-2205 |
| 47 | Valdivia | SI-85 | 4170±90 | 2915-2495 |
| 48 | Valdivia | M-1318 | 4170±140 | 3040-2320 |
| 49 | Valdivia | SI-16 | 4220±100 | 3035-2495 |
| 50 | Real Alto | ISGS-467 | 4140±190 | 3310-3225 (3%) 3125-2175 (92%) |
| 51 | Valdivia | SI-80 | 4140±60 | 2880-2570 |
| 52 | Valdivia | SI-82 | 4120±65 | 2880-2560 (89%) 2535-2495 (6%) |
| 53 | Valdivia | M-1321 | 4100±140 | 2925-2205 |
| 54 | Real Alto | GX-7429 | 4050±185 | 3040-2035 |
| 55 | Real Alto | GX-7430 | 3845±240 | 2910-1680 |
| VALDIVIA PHASE 4 | ||||
| 56 | Valdivia | W-630 | 4050±200 | 3095-2015 |
| 57 | Buenavista | SI-71 | 4040±55 | 2865-2810 (9%) 2745-2455 (86%) |
| 58 | P.Concep. | L-1232H | 3900±150 | 2870-2805 (3%) 2770-1950 (92%) |
| 59 | Valdivia | SI-78 | 3970±65 | 2620-2280 |
| VALDIVIA PHASE 5 | ||||
| 60 | Real Alto | GX-7437 | 4157±165 | 3310-3225 (3%) 3130-2280 (92%) |
| 61 | Real Alto | GX-7436 | 4145±170 | 3300-3235 (2%) 3105-2195 (93%) |
| VALDIVIA PHASE 6 | ||||
| 62 | Real Alto | GX-7438 | 4204±160 | 3330-3220 (4%) 3135-2340 (91%) |
| 63 | Real Alto | GX-7334 | 4015±170 | 2920-2030 |
| VALDIVIA PHASE 7 | ||||
| 64 | Real Alto | GX-7439 | 4050±185 | 3040-2035 |
| 65 | La Emerenciana | SMU-4259 | 4109±215 | 3330-2040 |
| 66 | Anllula | P-2761 | 4020±220 | 3095-2895 |
| VALDIVIA PHASE 8 | ||||
| 67 | Ayalan | N-2908 | 3665±95 | 2290-1750 |
| 68 | Ayalan | N-2909 | 3630±105 | 2285-1650 |
| 69 | San Isidro | ISGS-1221 | 3630±70 | 2190-1860 (86%) 1845-1775 (9%) |
| 70 | San Isidro | ISGS-1222 | 3620±70 | 2140-1760 |
| 71 | San Isidro | ISGS-1223 | 3560±70 | 2115-2085 (3%) 2040-1690 (92%) |
| 72 | San Isidro | ISGS-1220 | 3500±70 | 1970-1630 |
| 73 | San Isidro | PIT-426 | 3545±135 | 2205-1520 |
| 74 | Anllula | N-2909 | 3630±105 | 2285-1690 |
| 75 | Anllula | N-2908 | 3660±95 | 2295-1750 |
| 76 | La Emerenciana | SMU-2263 | 3775±165 | 2620-1740 |
| 77 | La Emerenciana | SMU-2225 | 3707±148 | 2485-1690 |
| 78 | La Emerenciana | SMU-4549 | 3629±303 | 2875-1300 |
| 79 | La Emerenciana | SMU-2226 | 3400±220 | 2305-1130 |
| 80 | La Emerenciana | SMU-2241 | 3361±246 | 2305-1010 |
radiocarbon dates from Valdivia Culture. Dates included to calibration: | |||
|---|---|---|---|
BP |
|||
| PHASE 1a | |||
| 1 | Real Alto | ISGS-448 | 5260±256 |
| 2 | Real Alto | GX-5267 | 5495±200 |
| 3 | Loma Alta | I-7076 | 5010±120 |
| 4 | Loma Alta | ISGS-142 | 5000±190 |
| 5 | Loma Alta | GX-7704 | 5275±175 |
| PHASE 1b | |||
| 1 | Real Alto | GX-5268 | 4900±170 |
| 2 | Real Alto | ISGS-452 | 4700±300 |
| 3 | Loma Alta | I-7075 | 4920±120 |
| PHASE 2a | |||
| 1 | Colimes | ISGS-477 | 4525±75 |
| 2 | Colimes | ISGS-478a | 4510±100 |
| 3 | Colimes | ISGS-478b | 4460±100 |
| 4 | Real Alto | GX-5266 | 4495±160 |
| 5 | Real Alto | ISGS-452 | 4700±300 |
| 6 | Real Alto | ISGS-468 | 4760±120 |
| 7 | Loma Alta | ISGS-192 | 4590±120 |
| 8 | Loma Alta | ISGS-146 | 4760±120 |
| 9 | Loma Alta | GX-7699 | 4630±160 |
| PHASE 2b | |||
| 1 | Real Alto | ISGS-466 | 4390±75 |
| 2 | Real Alto | ISGS-439 | 4110±75 |
| 3 | Real Alto | ISGS-446 | 4265±75 |
| 4 | Valdivia | HV-4838 | 4260±100 |
| 5 | Loma Alta | SI-1055 | 4370±65 |
| 6 | Loma Alta | HV-4673 | 4335±100 |
| 7 | Colimes | GX-5271 | 4365±245 |
| PHASE 3 | |||
| 1 | Real Alto | GX-7429 | 4050±185 |
| 2 | Real Alto | ISGS-467 | 4140±190 |
| PHASE 8 | |||
| 1 | Ayalan | N-2908 | 3665±95 |
| 2 | Ayalan | N-2909 | 3630±105 |
| 3 | San Isidro | ISGS-1221 | 3630±70 |
| 4 | San Isidro | ISGS-1222 | 3620±70 |
| 5 | San Isidro | ISGS-1223 | 3560±70 |
| 6 | San Isidro | ISGS-1220 | 3500±70 |
| 7 | San Isidro | PIT-426 | 3545±135 |
interval [calendar years BC] |
interval [calendar years BC] |
interval [calendar years BC] |
|
| Phase 1a | 4340 to 3830 | 4460 to 3755 | 4820 to 3515 |
| Phase 1b | 3780 to 3455 | 3860 to 3340 | 4020 to 2835 |
| Phase 2a | 3475 to 3135 | 3555 to 3065 | 3765 to 2905 |
| Phase 2b | 3030 to 2765 | 3090 to 2695 | 3335 to 2510 |
| Phase 3 | 2810 to 2455 | 2870 to 2360 | 3205 to 2080 |
| Phase 8 | 2030 to 1830 | 2090 to 1790 | 2240 to 1665 |
| Valdivia phases | 14C dates 68%CI | TL chronology | BC chronology (10) |
| Phase 8b | 1600-1450 BC (11) | ||
| Phase 8 | 2090-1790 BC | 1700-1500 BC | 1800-1600 BC |
| Phase 7 | 1900-1700 BC | 1950-1800 BC | |
| Phase 6 | 2100-1900 BC | 2100-1950 BC | |
| Phase 5 | 2400-0100 BC | 2250-2100 BC | |
| Phase 4 | 2600-2400 BC | 2400-2250 BC | |
| Phase 3 | 2870-2360 BC | 2900-2400 BC | 2800-2400 BC |
| Phase 2b | 3090-2695 BC | 3200-2900 BC | 3300-2800 BC |
| Phase 2a | 3555-3065 BC | 3300-3000 BC | |
| Phase 1b | 3860-3340 BC | 3600-3200 BC | 3800-3300 BC |
| Phase 1a | 4460-3755 BC | 4400-3800 BC |
Loma Alta (12) 14C determinations according to Archaeological Phase and Stratigraphic Association |
||
| Laboratory | BP determination | Archaeological stratigraphic association |
| Valdivia 2b | ||
| ISGS-190 | 3765± 85 BP | Unit J-III 2.10m. bs. |
| HV-4673 | 4335±100 BP | Unit J-II 1.60m. bs. |
| SI-1055 | 4370± 65 BP | Unit J-II 1.70m. bs. |
| Valdivia 2a | ||
| ISGS-192 | 4590±120 BP | Unit J-III 2.20m. bs. associated with Cairn (13) N_8 |
| GX-7699 | 4630±160 BP | From hearth in Valdivia 2a house floor |
| ISGS-146 | 4750±120 BP | Associated with Cairn N_1 Top of Cairn 1.90m. bs. |
| Valdivia 1b | ||
| I-7075 | 4920±120 BP | 14C sample taken below levels of Cairns |
| Valdivia 1a | ||
| ISGS-142 | 5000±190 BP | Below Cairn N_6 2m. bs. |
| I-7076 | 5010±120 BP | 14C sample taken below levels of Cairns |
| GX-7704 | 5275±175 BP | Hearth below Valdivia cultural deposits |
and Stratigraphic Association |
||
| Laboratory | BP determination | Archaeological stratigraphic association |
| Valdivia 7 | ||
| GX-7439 | 4050±185 BP | Charcoal Sample from feature F-197 bell shaped food preparation pit (14). |
| Valdivia 6 | ||
| GX-7434 | 4015±170 BP | Charcoal Sample from Wall Trench Structure S-13. (15) |
| GX-7438 | 4204±160 BP | Charcoal Sample from feature F-108 large “Fiesta” refuse pit. (16) |
| Valdivia 5 | ||
| GX-7436 | 4145±170 BP | Charcoal Sample from Wall Trench Structure S-38 (17) |
| GX-7437 | 4175±165 BP | Charcoal Sample from feature F-101 “Fiesta” refuse pit. (18) |
| Valdivia 4 | ||
| No Valdivia 4 Radiocarbon Samples were collected at Real Alto | ||
| Valdivia 3 | ||
| GX-7430 | 3845±240 BP | Charcoal Sample from Structure S-1, level (19) |
| GX-7429 | 4050±185 BP | Charcoal Sample from Structure S-1, level 2 (20) |
| Valdivia 2b | ||
| ISGS-439 | 4110± 75 BP | Valdivia 2 Mound burnt wattle and daub |
| ISGS-446 | 4265± 75 BP | Top of Valdivia 2 Mound |
| ISGS-466 | 4390± 75 BP | Trench C 0.70-0.80m. bs. |
| Valdivia 2a | ||
| GX-5266 | 4495±160 BP | Trench B bottom of Valdivia 2 Mound |
| ISGS-452 | 4700±300 BP | Trench B bottom of Valdivia 2 Mound |
| ISGS-468 | 4760±120 BP | Trench C 0.80-0.90m. bs. first Valdivia 2 occupation. |
| Valdivia 1b | ||
| GX-5268 | 4900±170 BP | Trench C Structure S-2-77 0.90-0.98m. bs. |
| Valdivia 1a | ||
| ISGS-448 | 5620±250 BP | Trench C 0.90-1.00m. bs. |
| GX-5267 | 5495±200 BP | Adjacent to S-2-77 0.95-1.02m. bs. |
| GX-5269 | 6195±215 BP | Bottom of Structure S-2-77 |
| Laboratory | BP determination | Archaeological stratigraphic association |
| Valdivia 8 | ||
| ISGS-1220 | 3500± 70 BP | San Isidro Valdivia 8 occupation |
| PIT-426 | 3545±135 BP | San Isidro Valdivia 8 occupation |
| ISGS-1223 | 3560± 70 BP | San Isidro Valdivia 8 occupation |
| ISGS-1222 | 3620± 70 BP | San Isidro Valdivia 8 occupation |
| ISGS-1221 | 3630± 70 BP | San Isidro Valdivia 8 occupation |
| Anllulla | ||
| Valdivia 8 | ||
| N-2909 | 3630±105 BP | Valdivia 8, below the Jambelí occupation |
| N-2908 | 3660± 95 BP | Valdivia 8, below the Jambelí occupation |
| Valdivia 7 | ||
| P-2761 | 4020±220 BP | San Isidro Valdivia 7 stratum below the Valdivia 8 occupation |
| La Emerenciana | ||
| Valdivia 8 | ||
| SMU-2241 | 3361±246 BP | Transition Valdivia 8/ Machalilla, ceramic content similar to Valdivia 8b from San Lorenzo del Mate |
| SMU-2226 | 3400±220 BP | Transition Valdivia 8/ Machalilla, ceramic content similar to Valdivia 8b from San Lorenzo del Mate |
| SMU-4549 | 3629±303 BP | Valdivia 8, below Valdivia 8b occupation |
| SMU-2225 | 3707±148 BP | Valdivia 8, below Valdivia 8b occupation |
| SMU-2563 | 3775±165 BP | Valdivia 8, below Valdivia 8b occupation |
| Valdivia 7 | ||
| SMU-4259 | 4109±215 BP | Valdivia 7, below Valdivia 8 occupation |
| Sample Number | Provenience (21) | Formal Class | TL determination |
| Valdivia 8 | |||
| 7248d | LV-U4-25 cmbs | 18 deep carinated bowl | 1620±289 BC |
| 7248c | “ | 35 carinated rim olla wm | 1602±329 BC |
| 7248b | “ | 8 deep incurved bowl | 1596±296 BC |
| 7248e | “ | Too small to reconstruct | 1523±310 BC |
| SLM-24-38 | SLM-U2-45 cmbs | 36 carinated rim olla cn | 1446±265 BC |
| SLM-24-41 | “ | 6 deep hemispheric bowl | 1422±245 BC |
| SLM-24-40 | “ | 36 carinated rim olla cn | 1410±260 BC |
| Valdivia 7 and Thin Orange Engraved and Punctated Ware (Protomachalilla) |
|||
| SLM-53-a | SLM-U2-65 cmbs | 36 carinated rim olla cn | 1916±265 BC |
| 7240a | RA-U2-30 cmbs | 6 deep hemispheric bowl | 1894±328 BC |
| SLM-53-64 | SLM-U2-65 cmbs | 42 Top for 36 | 1857±324 BC |
| 7249e | LV-U4-45 cmbs | 27 S-shaped neck olla | 1834±331 BC |
| 7249d | “ | 7 m. deep incurved bowl | 1819±375 BC |
| 7240b | “ | 7 hemispherical bowl | 1811±333 BC |
| 7240d | “ | 34 short curved neck olla | 1874±303 BC |
| SLM-53-59 | SLM-U2-65 | 40 carinated rim olla wm | 1763±286 BC |
| 7259a | LV-U4-45 cmbs | 3 flaring-wall deep plate | 1700±384 BC |
| Valdivia 6 | |||
| SLM-56-76 | SLM-U2-100 cmbs | 40 carinated rim olla wm | 2167±331 BC |
| SLM-56-84 | “ | 33 short neck globular olla | 2081±344 BC |
| 7220b | RA-U1-45 cmbs | 25 shallow bowl | 2052±353 BC |
| SLM-62-21 | SLM-U2-100 cmbs | 16 shallow carinated bowl | 2048±338 BC |
| 7220c | RA-U1-45 cmbs | 29 bell-shp. long neck olla | 2042±427 BC |
| 7220d | “ | ” | 2039±411 BC |
| 7220e | “ | 32 short bell-neck jar | 2037±300 BC |
| Valdivia 5 | |||
| 7241c | RA-U2-40 cmbs | 16 shallow carinated bowl | 2321±301 BC |
| 7241b | “ | 16 shallow carinated bowl | 2306±347 BC |
| 7241e | “ | 4 shallow hemisph. bowl | 2292±352 BC |
| 7220a | RA-U1-60 cmbs | 20 neckless olla | 2287±315 BC |
| 7241a | RA-U2-40 cmbs | 27 S-shaped neck olla | 2243±324 BC |
| Valdivia 4 | |||
| 7243d | RA-U2-55 cmbs | Undiagonistic body sherd | 2541±378 BC |
| 7243b | “ | 35 carinated rim olla wm | 2524±358 BC |
| 7243a | “ | Unidagonostic body sherd | 2458±331 BC |
| 7243c | “ | 6 deep hemispheric bowl | 2405±358 BC |
| Valdivia 3 | |||
| 7222e | RA-U1-80 cmbs | 23 folded rim l-neck olla | 2897±409 BC |
| 7222c | “ | 33 short-neck globular olla | 2829±404 BC |
| 7223a | “ | 25 S-shaped neck olla | 2829±381 BC |
| 7223e | “ | 17 deep carinated bowl | 2740±391 BC |
| Valdivia 2b | |||
| 7245b | PT-U3-18 cmbs | 22 folded rim olla | 3154±440 BC |
| 7245a | “ | 23 long neck f-rim olla | 3024±410 BC |
| 7245e | “ | 23 long neck f-rim olla | 2958±433 BC |
| 7246b | “ | 33 short neck globular olla | 2904±524 BC |
| 7246a | “ | 33 short neck globular olla | 2888±483 BC |
| 7245c | “ | 23 long neck f-rim olla | 2727±476 BC |
| Valdivia 2a | |||
| 7235a | RA-U1-100 cmbs | 19 deep neckless olla | 3270±426 BC |
| 7235b | “ | 32 short bell-necked jar | 3093±407 BC |
| 7234a | “ | 21 short-neck f-rim olla | 3052±436 BC |
| Valdivia 1b | |||
| 7238b | RA-U1-140 cmbs | 19 deep neckless olla | 3673±439 BC |
| 7238a | “ | 21 short-neck f-rim olla | 3577±454 BC |
| 7236a | “ | 33 short-neck globular olla | 3524±487 BC |
| 7238c | “ | 9 deep tetrapod bowl | 3388±424 BC |
| 7238d | “ | 9 deep tetrapod bowl | 3284±375 BC |
| 7236b | “ | 9 deep tetrapod bowl | 3149±496 BC |
| 7236c | “ | 33 short-neck globular olla | 3099±578 BC |
| 7236d | “ | 23 folded rim l-neck olla | 3078±435 BC |
NOTES
1 The 14C assay, with its margin of error, and the laboratory reference number, should be followed by B.P. (before present). When calendar years are reported, these should be followed by b.c. or a.d. (in lower case) if the dates are not calibrated. Calibrated dates should always be indicated by B.C. or A.D. (in capital letters).
2 Ronald Lippi (1983) in his unpublished doctoral dissertation at the Department of Anthropology, University of Wisconsin, Madison La Ponga and the Machalilla Phase of Coastal Ecuador, offered a new Machalilla sequence.
3 The project CERAMIC DATING BY THERMOLUMINESCENCE AND GEOLOGICAL DETERMINATION OF ARCHAEOLOGICAL MATERIALS SOURCE AREAS, provided a excellent validation of the Valdivia Chronology, complementing and expanding the scope of the existing 14C determinations(Alvarez, Marcos and Spinolo, 1995).
4 Since then, more precise methods of 14C dates calibration have been described by various authors. Several 14C/tree-ring dendrochronological calibration tables have been proposed by Suess (1967, 1970 ) Damon et. al (1974 ) Struiver, et. al.(1993).
5 See J. Marcos 1988, Real Alto. La Historia de un centro ceremonial Valdivia. (Primera Parte) Biblioteca Ecuatoriana de Arqueología Vol 4, pp. 144-145, fig. bottom page 144. ESPOL/CEN, Quito.
7 Forms of contamination before sampling are water logged sites where water dissolves the carbon from a samples and deposits it elsewhere, also the formation of mineral concretions around the carbon sample can be a problem. However the latter can be solved in the laboratory.
8 In order not to contaminate the sample this should be sealed within a clean container, such as a plastic bag, and its should be labeled outside the container. Carboard or paper labels should not be put inside the container.
9 These studies have been carried out by Aureli Alvarez and Jorge G, Marcos at the Archaeological Materials Service of the Universidad Autónoma de Barcelona, Bellaterra, Barcelona. See Alvarez, A., Marcos, J. And Spinolo G. (1995).
10 The BC chronology has been established through the comparative study of radiocarbon dates and TL dates, in relationship with the relative rate of deposition at Real Alto and San Lorenzo del Mate.
11 Phase 8b is proposed based on ceramic sequence at San Lorenzo del Mate, and the TL dates from the upper deposit of Unit 2b. The appearance of pedestal plates and compoteras in this context suggests that there is a distinct assemblage after the Valdivia Phase 8 proposed by Hill. We are provisionally referring to it as phase 8b, although in the future, after a close comparison with the Vlaidivia-Machalilla transitional phase defined by Staller (1994), it may be better to refer to it as Valdivia Phase 9.
12 Loma Alta is a Valdivia 1a-2b occupation covered by an Engoroy phase occupation.
13 The so called Cairns, both at Loma Alta and Real Alto, proved to be Manos and Metates kept (or sacrificed) at the bottom of Valdivia 2a bell-shaped storage pits. Sometime these sacrifices contained vessels and burials. (see foot note 3)
14 This determination is too old for Valdivia 7 even when calibrated it is closer to Valdivia 4 dates. This could be due to reuse of long lasting building material as firewood.
15 This determination is again too old for Vakdivia 6, it may be due to reuse of long lasting building material.
16 This aberrant date may result from the use of old building material as firewood
17 Although expected date falls within the lower part of this determination interval, it may also be due to the reuse of old building material.
18 Date falls within lower part of the calibration interval. However reuse of building material for cooking fires might account for slightly older than expected date
19 This date falls on the upper part of the calibration interval.
20 This date is more in alignment with Valdivia 3 expected dates.
21 SLM = San Lorenzo del Mate; RA = Real Alto; LV = Loma de los Villones; PT=Punta Tintina
