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Good Dates and Bad Dates in Ecuador

 

Radiocarbon Samples and Archaeological Excavation: a Commentary Based on the "Valdivia Absolute Chronology"
Jorge G. Marcos
Universidad Autónoma de Barcelona
Departemento de Geologia, Edificio CS
08193 Bellaterra
Barcelona, España.
Adam Michczynski
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.


REFERENCES
Alvarez, A., Marcos, J. G., Spinolo, G.
1995, The Early Formative pottery from the Santa Elena Peninsula in Southwest Ecuador. In Studies on Ancient Ceramics, Proceedings if the European Meeting on Ancient Ceramics. Vendrell-Saz, M., Pradell, T., Molera, J., & Garcia, M. eds. Barcelona: Generalitat de Catalunya, Department de Cultura. Pp. 95-107.

Atchinson, T., Ottaway, B. and Al-Ruzaiza, A.S.
1991, Summarizing a group of 14C dates on the historical time scale: with a worked example from the Late Neolithic of Bavaria. Antiquity 65 (246): 108-116.

Bischof, H.
1975a, El Machalilla Temprano y algunos sitios cercanos a Valdivia. Bonner Amerikenistischen Studien 3, U. Oberem (ed.) pp. 41-62, Bonn.
1975b, La fase Engoroy, periodos, cronología y relaciones. Bonner Amerikenistischen Studien 3, U. Oberem (ed.) pp.13-38, Bonn.

Bischof, H., Viteri Gamboa, J.
1972, Pre-Valdivia occupations on the Southwest coast of Ecuador. American Antiquity 37 (4):548-551.

Damon, P. E., Ferguson, C. N., Long, A., Wallick, E. I.
1974, Dendochronologic Calibration of the Radiocarbon Time Scale. American Antiquity 39 (2):350-366.

Hill, B. D.
1972/74, A new chronology for Valdivia ceramic complex from the Guayas Province, Ecuador. Ñawpa Pacha 10/12: 1-32, Berkeley: Institute of Andean Studies.

Libby, W. F.
1955, Radiocarbon Dating. Second edition, Chicago: The University of Chicago Press.

Marcos, J. G.
1978, “The Ceremonial Precinct at Real Alto: organization of Time and Space in Valdivia Society.” PhD. dissertation, University of Illinois at Urbana-Champaign. Ann Arbor. Michigan: University Microfilms International N_7913541.
1979, Woven Textiles in a Late Valdivia Context (Ecuador). Junius B. Bird, Pre-Columbian Textile Conference, May 19th and 20th, 1973. A.P. Rowe, E.P. Benson, A.L. Schaffer eds., Washington, D. C.: The Textile Museum & Dumbarton Oaks, Trustees for Harvard University.
1988, Real Alto: La Historia de un Centro Ceremonial Valdivia. Biblioteca Ecuatoriana de Arqueología. Vols. 4 y 5, Quito: ESPOL/CEN.

Marcos, J. G., Alvarez S. G.
1989, Proyecto Arqueológico, Antropológico y Arquitectónico, San Lorenzo del Mate. Convenio Banco Central del Ecuador/Fundación Pedro Vicente Maldonado. Informe Final. Guayaquil: Fundación Pedro Vicente Maldonado.

Meggers, B. J., Evans, C. and Estrada, E.
1965, The Early Formative Period of Coastal Ecuador: The Valdivia and Machalilla Phases. Smithsonian Contributions to Anthropology N_1. Washington, D.C.: Smithsonian Institution.

Norton, P.
1972, “Early Valdivia Middens at Loma Alta, Ecuador”. Paper read at the 3th Annual Meeting of the Society for American Archaeology, Balharbour, Florida

Ottaway, B.
1993, Dispersion diagrams: a new approach to the display of 14C dates. Archaeometry 15(1): 5-12.

Pazdur, M. F., Michczynska, D. J.
1989, Improvement on the procedure for probabilistic calibration of radiocarbon dates. In Long, A., Kra, M. S. amd Srdoc. D. eds. Proceedings of the 13th International 14C Conference. Radiocarbon 31 (3) 824-832.

Renfrew, C., Bahn, P.
1991, Archaeology: Theory, Methods and Practice. London: Thames and Hudson.

Stuiver, M., Long A. and Kra R. S. eds.
1993, Calibration 1993. Radiocarbon 35 (1):1-244.

Staller, J. E.
1994, “Late Valdivia Occupation in Southern Coastal El Oro Province, Ecuador: Excavations at the Early Formative Period (3500-1500 B.C.) Site of La Emerenciana”. Unpublished Ph.D. Dissertation, Dedman College, Southern Methodist University, Dallas, Texas.

Suess, H. E.
1967, Bristlecone pine calibration of the radiocarbon time scale 4100 B.C. to 15 B.C. In Radioactive dating and methods of low-level counting, Viena: International Atomic Energy Agency. Pp: 143-151.
1970, Bristlecone pine calibration of the radiocarbon time scale 5200 B.C. to present. In Radiocarbon variations and absolute chronology. Olsson, I. U., ed., New York: John Willey & Sons. Pp: 303-309.

Vescelius, G. S.
n.d., A Reapprisal of Radiocarbon dating (1973) MS.

Zeidler, J. A.
1984, “Social Space in Valdivia society: Comunity patterning and domestic structure at Real Alto, 3000-2000 BC.” PhD. dissertation, University of Illinois at Urbana-Champaign. Ann Arbor. Michigan: University Microfilms International N_8422183

Ziólkowski, M. S., Pazdur, M. F., Krzanowski A. and Michczynski A. eds.
1994, ANDES. Radiocarbon Database for Bolivia, Ecuador and Peru. Andean Archaeological Mission of the Institute of Archaeology, Warsaw University & Gliwice Radiocarbon Laboratory of the Institute of Physics, Silesian Technical University, Warsaw-Gliwice. 1-604.


TABLE 1
GdCALIB REPORT:
calibration of set of unrelated radiocarbon dates
No
Site
Labcode
Radiocarbon age
BP
95% confidence interval
[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

TABLE 2
Composite probability distribution of calibrated
radiocarbon dates from Valdivia Culture.
Dates included to calibration:
No
Site
Labcode
Radiocarbon age
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

TABLE 3
 
50% confidence
interval
[calendar years BC]
68% confidence
interval
[calendar years BC]
95% confidence
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

TABLE 4. VALDIVIA CHRONOLOGY
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

APPENDIX 1
Valdivia 14C Determinations
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
Real Alto 14C determinations according to Archaeological Phase
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
Radiocarbon Determinations for San Isidro, Anllulla and La Emerenciana, San Isidro (Northern Manabí)
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

APPENDIX 2
Thermoluminescence Age Determinations from Real Alto, Punta Tintina, Loma de los Villones, and San Lorenzo del Mate Ceramics.
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.

6 Addition by J. G. Marcos

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


Figure 1A

Figure 1B

Figure 2