Subsidence and aggradation in the region

Aggradation, Axios Delta National Park. Note the sand.

The Aegean Sea Plate undergoing subsidence because of back-arc extension behind the Hellenic arc, the Aegean Sea is a classic example of drowned terrain: islands fronted by steep cliffs formed from mountain-tops, submergent coastlines with long estuaries formed by flooding from the sea. Acting contrary to the submergence is aggradation. Drowned rivers dump their sediment into their new estuaries creating river deltas. The deltas eventually combine to form alluvuial shelves and valleys, which, in the Aegean, typically became agricultural areas.

Over any period, an aggraded shoreline is the result of an equilibrium between subsidence and aggradation. Subsidence pushed the coastline inland; aggradation brings it out. The equilibrium may be cyclical, or it may trend in one direction.

Core studies in the C. Macedonian Plain compared with core studies from the whole Mediterranean have established that throughout the Aegean the rate of subsidence is on the average a little less than a metre per thousand years, which expresses itself as a rise in sea level to an observer at the surface.^[1] Bintliff calls this a "eustatic rise."

The shoreline at any isochron; that is a line on the basin wall every part of which has the same date, obviously depends on the configuration of the surface between the location of the foot of the core and the concurrent shoreline. The more core samples that are available, the better the geologist can detail the surface. All models retain an element of speculation. In the case of the C. Macedonian Plain, Bintliff combines geological data with historical sources to develop a brief history of shorelines there.

Imathia, but not Emathia. In the time before Emathia became Macedonia, the area shown was part of the Thermaic Gulf. The Loudias River shown here did not exist. Emathia was elsewhere, undoubtedly north.

On the map, the Plain is the green area at the mouth of the Axios, today's Vardar River. Stretching across the Vardar, it extends E-W from Thessaloniki to Naoussa, a distance of about 73.42 km (45.62 mi), and N-S from Giannitsa to Vergina, about 34.53 km (21.46 mi). This is approximately the location of modern Imathia. The latter country, however, is distinguished from the ancient by not having been there. In its place was either a shallow estuary of the Thermaic Gulf, or a lake in a marsh, from prehistoric times to nearly the present. Ancient Emathia can only have been further north, but of course at the time when the name was changed, Emathia was all of Macedonia.

The white clay layer

Geologists of the 19th and 20th centuries formulated a number of geologic models of the central Macedonian plain, but few were as useful those based on the excavation of Nea Nikomedeia (NN), 1961, 1963-64, under the direction of Rodden and Grahame Clark.^[2] NN is a Neolithic site at 40°36′15″N 22°15′54″E / 40.604156°N 22.264982°E / 40.604156; 22.264982, within the borders of Veria (Beroia), ancient capital of the Macedonian League, at the SW edge of the Plain.^{[lower-alpha 1]}

Early Neolithic house at Nea Nikomedeia. Note the white traces of the subsoil level showing through.

The mound of NN rose to a height of 3.5 m (11 ft) over an undisturbed subsoil layer of "white carbonate silt," with a disturbed portion of it rising another 0.5 m (1.6 ft).^[3] The silt was classified by the excavators as lacustrine.^[4] It was pollen-free.^[5] Although it had accumulated under a lake, it was high and dry when the settlers built on it.^[6]

This same layer was found at the bottom of an excavated drainage ditch 100 m to the SW, the layer's surface being at 7 m above current sea level.^[3] NN seems to have been constructed on a mound of it. The layer in the ditch, however, represents ground level.

In fact the worldwide graph of sea level versus millenia bp shows a slope approximating a straight line at a steep angle until about 8000 bp, when it breaks, becomes shallow, and at about 6000 bp ceases to show subsidence, except for a dampened sinusoidal curve excursing cyclically above and below sea level. This fluctuation explains why the white layer appears above sea level. Currently there is no subsidence, explaining why aggradation has the upper hand. The flood basins are all full of silt, extending the shorelines outward.^[7]

In 1965 a core, subsequently named GIANNITB, taken by Syte Bottema from the central area of the alluvium 7.5 km (4.7 mi) to the NW along a line to Gianitsa,^{[lower-alpha 2]} revealed a physically similar white clay layer, believed to be of the same surface, at a depth of 12.52 m below the current sea level.^[5] The bottom layer is described as being between 12.3900 m and 12.6500 m, consisting of "light-grey, marly clay."^[8]

There is dating available on NN.^{[lower-alpha 3]} The earliest settlement there, termed "the Early Neolithic" (EN), is dated 5500-5300 BC based on C-14 dates,^[9] which, allowing 1950 for the AD time,^{[lower-alpha 4]} would be 7450-7250 BP, the 8th millenium BP. A subsequent layer of detritus suggests an abandonment followed by a "Late Neolithic" reoccupation during which the ditch was dug.^[9] The EN, being directly on the white layer, places the layer at settlement in the 8th millenium BP.

There is a problem with applying the general rate of subsidence to GIANNITB. According to it, the whole layer should be dated to the 13 millenium BP. At NN, it is dated to the 8th. Obviously, the standard rate cannot apply to the core if the layer at both places really is the same.

The lakeside cliff hypothesis

Having perceived the contradiction, and realizing the need to calibrate the plot of core meters^{[lower-alpha 5]} versus BP dates; that is, to associate points within the plot with known data, Bottema acquired two carbon dates from material in the core, one from 6.525 m, and one from 9.950 m.^[10] Very likely, both were done in the same year, 1965.

The 6.525 m date was 6590 ± 110 BP, which falls into the 6th millennium within the layer 6.58-6.8 m, described as "blue-grey clay," with an average depth of 6.69 m. The 9.950 m date was 7.27 ± 70 BP, which falls into the 8th millennium within the layer 9.74-10.91, described as "grey or blue-grey clay + shell fragments," with an average depth of 10.325 m. As it turns out, a number of weak points would develop in Bottema's interpretation of the core. He was so certain of his calibration of the carbon dates that he used BP, but that use was one of the first things questioned. Also, was the layer to be considered 9th or 10th millenium? And finally, was not the grey clay part of the white layer, which was supposed to be below 12.52 m?

In addition to the qualitative information such as plant and soil type, the core is a quantitative record of depth versus time period, which can be graphed in a Cartesian coordinate system with depth in the y direction and time in millennia (mill) in the x direction. The slope of the line at any point is the sedimentation rate in meters per millenium (m/mill.).

The graph of this core has only two known slopes, one of 6.525/6.59=0.99 m/mill, very nearly the standard subsidence rate of 1. At 6.525 the slope changes, with the new slope applying from 6.525 m to the end, 12.52 m. The known point is (9.950 m, 7.27 mill.). Δy/Δx from the previous point is 5.04 m/mill., a sedimentation rate far above standard, filling in the core much faster. The total mill. at 12.52 m is 7.778, within 8 mill., instead of the projected standard 13.

The problem seems solved except for one thing. Bottema's study of the pollen led him to assert that at the beginning of settlement at NN the sea level was 6-9 m below present (and not 12.52 m).

The tilted layer hypothesis

The prehistoric plain

Bintliff's reconstruction of the early Plain of Central Macedonia is as follows. The region derives ultimately from a calcic lake in a subsiding region during the Pliocene (5.33-2.58 Mya). The white, calcareous layer crystallized out of solution and was deposited over the bottom in a layer about 1 m thick. The phase lasted through the mid-Pleistocene (1.25-0.7 Myr).

In the Late Pleistocene (129,000-11700 ya) through the Early Holocene (11650-8200 bp), the lake dried up, exposing the white layer, from which weathering removed the pollen. This is the time when the white layer was probably continuous and simultaneous, with no detritus over it, at NN. Two m of alluvium at the core, however, indicate a contemporaneous slope of the layer between NN and there. The sea level was 6-9 m bp. At the C-14 date of 7270 bp the plain would have appeared as a dry, bright surface with a mound at the future NN. There were none yet to settle it.

Evidence of the Giannitsa core

The Giannitsa core's validation by carbon dating of the dates and sequences of sedimentary events in the central Macedonian plain from the 8th millenium made possible the credible reconstruction of shorelines there. Bintliff offers four, which he combines with the literary and archaeological evidence to chronicle the successive occupation of the plain and the rise of Macedon in it. Before the Neolithic, it was not settled, and not permanently occupied. One of the characteristics of the Neolithic is first-time permanent settlement. Sometimes it begins in the Mesolithic, but there is no evidence of that here. The settlers, whoever they were, began on unoccupied land.

Earliest known name of Paeonia

Polybius (23.10.4) mentions that Emathia was earliest called Paeonia and Strabo (frg 7.38) that Paeonia was extended to Pieria and Pelagonia. According to N. G. L. Hammond,^[11] the references are related to Bronze Age period before the Trojan War.

Under the name of Emathia

Homer,^[12] who makes no mention of Macedonia, places Emathia as a region next to Pieria.

but Hera darted down and left the peak of Olympus; on Pieria she stepped and lovely Emathia, and sped over the snowy mountains of the Thracian horsemen, even over their topmost peaks, nor grazed she the ground with her feet; and from Athos she stepped upon the billowy sea, and so came to Lemnos, the city of godlike Thoas

The Homeric name was renewed mainly in Roman times and Ptolemy mentions some cities of Emathia. In Nonnus, Dionysiaca 48.6 Typhoeus having stripped the mountains of Emathia, he cast the rocky missiles at Dionysus. In Ovid, Metamorphoses 5.313 the daughters of Pierus say: "we grant Emathia's plains, to where uprise Paeonia's peaks of snow".^[13]

The change to Macedonia

The Emathian or Emathius dux is a frequently used name by Latin poets for Alexander the Great, as in Milton, the Emathian conqueror. Strabo relates that "what is now called Macedonia was in earlier times called Emathia"^[14] but since Homer, the earliest source considers Emathia only a region next to Pieria, Strabo's reference should be interpreted in the Roman era context of Emathia's name reviving. The same stands for Latin writers^[15] who name Thessaly as Emathia; the Roman province of Macedonia included Thessaly. In 12.462 of Metamorphoses, an Emathian named Halesus is killed by the centaur Latreus and in Catullus 64. 324, Peleus is Emathiae tutamen (protector).