Problems of Interpretation of the Akrotiri Radiocarbon Dates

These early dates cannot be correlated with either the other radiocarbon evidence for the Aegean at this time period or with the historical / archaeological chronology based on Egyptian and Near Eastern correlations. The radiocarbon evidence for the preceeding MM III / MH III and following LM IB / LH IIA periods is examined. While the MM III / MH III dates might suggest that the LM IA period can not have begun in the seventeenth century B.C. as the Theran series may indicate, analyses from the successive LM IB period seem to favor the early chronology. No explanation for this situation is possible from the present evidence.

The recent publication of a new series (Series I) of radiocarbon dates from the Late Minoan IA destruction of Akrotiri, Thera, has focused attention on this time period because of the early nature of the series (Michael, 1976; Betancourt and Weinstein, 1976) (See Table). These dates include both long-lived and short-lived samples. When calibrated with the MASCA correction factor (Ralph, Michael and Han, 1973), the short-lived samples are more than a hundred years earlier than the "traditional" dates for the period. The late Spiridon Marinatos, for example, suggested a date from before 1550 B.C. to ca. 1500 B.C. for the Late Minoan (LM IA) period (Marinatos, 1972).

A second series (Series II) of radiocarbon dates from Akrotiri has further confused the situation (Weinstein and Michael, 1977) (See Table). This entire series, also equally divided between long and short-lived samples, was collected from pithoi in  Room 5 on the ground floor of the West House. Unlike Series I, which is internally consistently early, Series II is not only internally inconsistent, but it is inconsistent with the dates for Series I. At most, it can be said that the Late Minoan IA radiocarbon dates from Akrotiri suggest an early trend. Yet, both series are problematical. It has been suggested that special phenomena associated with the volcanic eruption may have affected the organic material, and thus in turn the radiocarbon dates (Chatters, Crosby, and Engstrand, 1969; Sulerzhizky, 1970; Betancourt and Weinstein, 1976; Weinstein and Michael, 1977). Whatever the explanation may be, we must proceed carefully, especially in attempting to utilize the Theran radiocarbon dates for chronological purposes.

There is obviously a discrepancy between these radiocarbon dates and the absolute chronology of the Aegean world as derived from Eastern connections (Betancourt and Weinstein, 1976). On the evidence of the radiocarbon dates, this discrepancy seems to be somewhat greater than a century but less than two centuries.

Several questions have been raised about these dates. Among them are:

1. How consistent are these results with other radiocarbon evidence from the Aegean at this time period?
2. What radiocarbon evidence is there for those periods immediately preceeding and following the LM IA period, that is Middle Minoan III / Middle Helladic III (MM III / MH III) and Late Minoan IB / Late Helladic IIA (LM / LH IIA), and how do the LM IA dates fit in with them?
3. Are all of the Aegean dates too early, or does the phenomenon seem to vary with the period of the sample being analyzed?

One check on the earliness of the Theran samples may be offered by the radiocarbon dates from the Middle Minoan III / Middle Helladic III period.

These dates are given in a list at the end of this paper. They have been calculated with the 5730 half-life and calibrated with the 1973 MASCA correction factor (Ralph, Michael, and Han, 1973). There are nine dates for the MM III / MH III period. Five are from Crete, two from Ayia lrini, Kea, and two from Ayios Stephanos on the Greek mainland. All were charcoal samples. Dates such as P - 1353 from Knossos and P - 1784 from Kato Zakro are late and one can only assume that they were contaminated by humic acids absorbed through percolating ground water (Bailey and Birrell, 1971; Grant-Taylor, 1971; Michael and Ralph, 1971; Tate, 1971; Betancourt and Weinstein, 1976). P - 2571 from Ayios Stephanos dated early at 2070 ± 230 B.C. and most likely the sample was once part of an older structural element (beam) from a building. Gif - 255 from Mallia and P - 1265 from Palaikastro (associated with MM III pottery) yielded dates of 1950 - 1920 ± 260 B.C. and 1800 ± 80 B.C., respectively, also earlier than the traditionally accepted dates of ca. 1700 - 1570 B. C. for the MM III period.

The remaining four dates seem to fit the historical and archaeological picture quite well. P - 2444 from Knossos at 1910 - 1780 ± 90. B.C. and P - 2581 from Ayia Irini at 1850 - 1770 ± 70 B.C. fit the upper limit of the period, while P - 2575 from Ayia Irini at 1710 - 1690 ± 60 B.C. falls well within MM III.

The final date from Ayios Stephanos, P - 2568, from a transitional MH / LH I context falls at the lower limits of the period with a date of 1510 ± 60 B.C.

On the basis of general agreement on the contemporaneity of the LM IA period with LH I, these last four dates suggest that the LM IA period can not have begun in the seventeenth century B.C. as the Theran dates might indicate.

For the Late Minoan IA/ Late Helladic I (LM IA / LH I) period, there are eleven radiocarbon dates in addition to the Theran dates. Again, they can be broken down into early, acceptable, and late dates. Crete, Kea and the Greek mainland are represented in this group of samples. P - 1354 from Knossos, P - 1401 and L - 362 from the Phira Quarries on Thera, and P - 2574 from Ayia Irini are all early. Since they were all wood samples, older dates are not unusual. It should be noted that both Theran samples here are in agreement with the early dates of Theran Series I. P - 1619 from Akrotiri and P - 1784 from Kato Zakro (the latter a transitional MM IIIB / LM IA sample) are both late and this is again probably a case of contamination before collection. The remaining five samples all fall within acceptable limits; P - 1355 from Knossos at 1490 ± 70 and P - 2568 from Ayios Stephanos at 1510 ± 60 B.C. are both good dates falling well within the LM IA period. Gif - 256 from Mallia has such a large statistical uncertainty that it could fit several historical periods. P - 1599 from Akrotiri at 1460 ± 160 B.C. was an undersized sample and althought the date is acceptable, caution should be used in its interpretation. P - 1697 from Thera (between Akrotiri and Megalochori), the only short-lived sample (beans) of this group, fits within the extreme lower limits of the traditional date of ca. 1550 -  1500 B.C. Analyses of these miscellaneous LM IA radiocarbon dates unfortunately do not help to clarify the problems raised by the Theran samples.

The fourteen radiocarbon dates for the following Late Minoan IB / Late Helladic IIA (LM IB / LH IIA) period might also offer a convenient check on the LM IA dates. Fortunately, the pottery from this period is fairly well understood, and the relationship between the two periods is well documented. The traditional date for LM IB / LH IIA is ca. 1500 - 1450 B.C. There are many LM IB destructions in the Aegean and all are apparently contemporary or nearly contemporary on the basis of ceramic evidence. Thus a radiocarbon date from one site should yield results that may be compared with sites in other parts of the Aegean. There are fourteen radiocarbon dates available, including some new dates from Pyrgos, Myrtos on Crete (Cadogan, 1977) and Ayia Irini on Kea.

Only two of the dates are from short-lived samples and both are from Pyrgos, Myrtos; they are bitter vetch (charred grain and soil) and hulled six-row barley, and in both cases, although within ten years of each other in date, they are too early. Their dates, P - 2113 at 1680 ± 60 B.C. and P - 2114 at 1690 ± 60 B.C. are not only early, but they are even earlier than the archaeologically earlier LM IA dates from Thera. Only one date (P - 1356 from Knossos) is too late.

Of the remaining eleven samples, eight are too early, while only three fall within acceptable limits. The two Palaikastro samples, St - 1263 (2050 ± 70 B.C.) and St - 1264 (2040 ± 120 B.C.) are much too early. St - 1264 was wood from a door threshold and St--1263 was charcoal, possibly part of the roof construction fallen into a pithos during the LM IB destruction. The remaining early charcoal dates are from Pyrgos (P - 2115, P - 2116, P - 2343, and P - 2344A) and Ayia Irini (P - 1284 and P - 2579). Several of these early dates (P - 2115, P - 2344A, P - 1284 and P - 2579) agree with the two shortlived dates from Pyrgos, Myrtos (P - 2113 and P - 2114). The only three dates which are in agreement are all from Ayia Irini in the northern Cyclades; they are P - 1282 at 1490 ± 50 B.C., P - 1283 at 1400 - 1380 ± 60 B.C. and P - 2576 at 1600 - 1570 ± 60 B.C. P - 2576 just barely falls within the extreme upper limits of the traditional chronology. In conclusion, the LM IB dates, like those from MM III and LM IA form an inconsistent group with an extremely wide range.

When one looks at the geographic distribution of the LM IB dates, a pattern may be suggested, though there are still too few dates to be sure. The dates from Crete and the southern Cyclades are all "early" with respect to the usually accepted chronology, but the majority of the dates from Kea, on the other hand are quite in keeping with what one should expect. Perhaps Kea's destruction was actually a little later (since it did have a small amount of LH IIB pottery present) (Caskey, 1972), or, is it possible that the early phenomenon does not extend to this more northern area? One cannot check this possibility from other sites of LM IA or LM IB date, and there are no dates at all from the Helladic equivalent LH IIA. There is, however, a new series of dates from Knossos, from the slightly later LM II period.

A newly processed series of samples was collected by Mr. M. Popham from the Unexplored Mansion at Knossos. This entire series of five samples dates consistently early (P - 2045, P - 2048, P - 2048A, P - 2046, P - 2047); in fact, the dates range from 3140 - 1600 B.C. All of the samples were wood, and since all were reported by the excavator to have been from structural elements of the building, the early dates were not unexpected. Unfortunately, this series is of no help to the problem. Two other dates, P - 1357 (1460 ± 70 B.C.) from Knossos, and P - 1282 (1490 ± 50 B.C.) from Ayia Irini are from wood; they are consistent and fall within the historical dates.

For the LM IIIA period, ca. 1400 / 1375 - 1275 / 1250 B.C., there are three dates from Knossos, all charcoal. P - 1358 at 1370 - 1320 ± 70 B.C. falls within acceptable limits, while P - 1359 at 1600 - 1570 ± 40 B.C. is early. A transitional LM IIIA / B date, also from Knossos (P - 2441 at 1400  - 1380 ± 60 B.C.) is in agreement with the historical dates.

Turning to the Greek mainland, there are three good series of LH III dates from Dendra (St - 1267, St - 1549), Mycenae, the Citadel House (P - 1454, P - 1455, P - 1456, P - 1457, P - 1459), Pylos (P - 254, P - 270, P - 326, P - 328, P - 329, P - 330, P - 332, P - 337, P - 340, P - 341, GrN - 998), and a single date from Tiryns (Grossmann and Schafer, 1975). The two short-lived sample dates from Dendra (figs) and the five Citadel House wood dates from Mycenae are in good agreement with the traditional chronology. Synchronisms with the Near East have established the end of LH IIIB as just before or after 1200 B.C. The series from Pylos forms a consistent group, with those from earlier strata yielding earlier dates.

While P - 254 and P - 270 are from slightly before LH IIIB, the remaining dates seem earlier than one might have expected, since the palace at Pylos must have been contemporary with the Citadel House at Mycenae. It has been seen that charcoal from timbers often yields extremely early results for Greek Bronze Age buildings. The explanation lies in the use of large trees whose outer growth rings would have been removed in the making of lumber, and in the length of time a building would stand. As the dates from Mycenae and Dendra demonstrate, there is no statistical problem in the correlation between the radiocarbon dates and the dates derived from the Near Eastern contacts. Two of the three analyses from Pylos taken from the latest LH IIIB strata (P - 337 and P - 341) are also within the correct range. Even if a slight problem is indicated, it is clearly not as great as for LM I.

For some as yet unexplained reason, there are more problems with the LM IA and LM IB dates from Thera and Crete than there are for earlier and later periods in the Aegean. In addition, the contemporary dates from Ayia Irini, Kea, do not yield problems of this magnitude. The Theran dates from Series I and some of the other dates (particularly the LM IB dates from Pyrgos Myrtos) suggest an early trend, but in view of the inconsistent results from Theran Series II, one must wait for more evidence before deciding both the nature and the extent of the problem.

If an early radiocarbon chronology does exist for LM I, it cannot be explained by choosing alternative interpretations of the archaeological evidence.

A small shift could be allowed by the Egyptian and Near Eastern correlations, but this would not be sufficient to explain the radiocarbon discrepancies (Betancourt and Weinstein, 1976). The radiocarbon technology also offers no explanation for the indicated conclusions. It is possible that one or more still unidentified factors affected the conditions in the Aegean basin or on Thera alone.

Whatever the explanation, one may close with a plea for new radiocarbon dates. New analyses of short-lived samples, collected carefully and firmly tied to a clear archaeological context, might contribute a substantial amount of new information as to whether a local phenomenon such as the eruption of Thera could cause short-term fluctuations which would produce anomalies in radiocarbon dates.

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