Absolute Dating

Despite the small quantity of radiocarbon dates available for the Quijos region, it is possible to make some important observations about the chronology of the region. Six dates were obtained through the Quijos Valley project and 12 more were available through Porras’ work (Table). Four of Porras’ dates (Porras 1975:147) are not included here, one that turned out to be modern, one that is too early (1495 ± 140 B.C), and two whose ceramic associations are not known because the level and excavation number provided in the list of radiocarbon dates do not match the chart in which the frequencies of ceramic types by level and excavation are provided. One of the dates produced by the Quijos project is not included either because it is also too early (1795 ± 33 B.C).

Unfortunately, all of Porras’ dates are associated with more than one ceramic type, and he does not provide enough detail in terms of stratigraphy or specific association of carbon samples with particular types. However, it is worth noting patterns related to the frequency of sherds of different types that are associated with each one of the dates.

All dates associated only or strongly with Cosanga pottery are later than the ones from contexts in which Cosanga was not the dominant type by at least 70% (with the exception of the second one, in which Cosanga constitutes only 12.5% of the material, and yet the date is late). This makes a strong case for arguing that Cosanga was the ceramic type in use at the time of the Spanish conquest, an observation supported by Lumbreras (1990), Delgado (2000), and Ontaneda (2002) that contradicts Porras’ argument that the region had been abandoned by approximately 700 A.D. Establishing a date when Cosanga became the predominant type in the region is less straightforward. The earliest date associated exclusively with Cosanga sherds is 1151 ± 32 A.D. Following this date, there are two dates associated with at least 70% Cosanga sherds, of which the earliest is 495 ± 170 A.D. The latter two, from Porras’ work, appeared with Borja sherds (I mentioned above how I believe that this type, which Porras believed dominant in the later portion of his sequence, is indistinguishable from Cosanga), and with Papallacta sherds. The general trend, as far as Porras’ dates are concerned, associates earlier dates with higher percentages of Papallacta sherds. As discussed above, I believe Papallacata may correspond to what I have called Bermejo Thick ceramics. If this evidence is used to assign beginning and ending points to the early occupation of the region, one could conceivably argue that this started by roughly 600 B.C. and gave way to a late occupation, in which Cosanga was the predominant type, by roughly 500 A.D. This is by no means a rigorous way of assigning dates to the early occupation of the region, and it should be considered only as a tentative proposition that requires further investigation. It is even more questionable to propose that the Early 1 and 2, if in fact they represent different periods, have a similar length of approximately 500 years arrived at by splitting the earliest and latest hypothetical range of the early occupation in two. This is proposed here with a great deal of hesitation. Alternatively, the Early 1 and 2 can be considered a single period, and in my analysis of settlement patterns I explore the two possibilities.

The scheme I propose here for the Late Period (500 - 1500 A.D.) matches the set of dates associated with Cosanga pottery in the northern and central highlands of Ecuador. A general look at all of the highland sites that have produced Cosanga ceramics, and their associated dates, indicates a late time range for the use of that pottery extending to the Colonial Period, including what is called the Integration Period. Reliable contexts with Cosanga pottery in the northern highlands, at the site of Cochasquí, yielded dates between 900 A.D. and 1300 A.D. (Oberem 1981). Further north, in the Chota-Mira Valley, Echeverria (1995) draws the association of Cosanga pottery with other local types between 700 A.D. and 1600 A.D. Likewise, Buys et al. (1994) place it in a range of 500 A.D. to 1500 A.D. based on samples from Cumbayá; where Uhle (1926) also found it associated with materials that more recently have been dated between 400 A.D. and 1000 A.D. Cordero (1998) also places the highest frequencies of Cosanga ceramics from her excavations in Cayambe between 950 A.D. and 1250 A.D. Dates associated with Cosanga pottery in the central highlands fall within similar ranges; Rodríguez (1991) reports three dates between 565 and 725 A.D. Other dates in the highlands point to earlier time ranges, for example, in excavations at La Chimba (Athens 1995), the levels where Cosanga sherds are more popular are dated between 40 B.C. and 120 A.D. Even so, it seems that the majority of dates associated to Cosanga pottery in the highlands falls in a range similar to the one proposed here based on the dates obtained from the Quijos region.

Once again, this is offered as a provisional frame of reference that will serve as a starting point for further investigation in the future. The early occupation is so small and hard to detect in the region that it was extremely difficult during the first field season of this project to target sites for absolute dating that did not have a late component. Obviously, one of the aims of future fieldwork is to find more deposits in which early ceramic types are predominant so that absolute dates for this occupation are available, as well as to acquire more dates for the late occupation.