Original paper
Returning to the facts: Response to the refusal of tsunami traces in the ancient harbour of Lechaion (Gulf of Corinth, Greece) by ‘non-catastrophists’ – Reaffirmed evidence of harbour destruction by historical earthquakes and tsunamis
Vött, Andreas; Hadler, Hanna; Koster, Benjamin; Matthes-Schmidt, Margret; Röbke, Björn R.; Willershäuser, Timo; Reicherter, Klaus
Zeitschrift für Geomorphologie Volume 61 Issue 4 (2018), p. 275 - 302
published: Jan 1, 2018
published online: Mar 1, 2018
manuscript accepted: Jan 15, 2018
manuscript revision received: Dec 21, 2017
manuscript revision requested: Dec 12, 2017
manuscript received: Nov 21, 2017
Open Access (paper may be downloaded free of charge)
Abstract
The ancient harbour of Lechaion supposedly was one of the most important harbours of the ancient world. Representing the western harbour of Corinth at the eastern end of the Gulf of Corinth, it was of major importance for commercial trade and military purposes. This paper is a response to the article by Kolaiti et al. (2017) who reject recent findings by Hadler et al. (2011, 2013) and Koster et al. (2013). The latter presented evidence of multiple tsunami impact on the harbour. Kolaiti et al. (2017) reassessed and interpreted historical, archaeological and climatological data concluding that there is no evidence that tsunami waves inundated the Lechaion site and that the overall tsunami potential in the eastern Gulf of Corinth is comparatively low. Instead, environmental changes in and around the ancient harbour are supposed to have been controlled by climatological factors, such as wind, swell and sea currents as well as human interventions. In this paper, we re-evaluate and synthesize geomorphological, stratigraphical and geochronological data published by Stiros et al. (1996), Morhange et al. (2012) and Hadler et al. (2013) and consider seismo-historical information collected by Mourtzas et al. (2014) and palaeoseismological data by Minos-Minopoulos et al. (2015). Based on geoscientific facts, the main statements of Kolaiti et al. (2017) are evaluated. From an epistemological point of view, the rationale brought forward by Kolaiti et al. (2017) that tsunami impact is not acceptable as long as historical evidence is missing, is untenable. Tsunami traces in geological archives dated by means of absolute dating techniques must not be rejected because they are not included in existing catalogues summarizing historical data. Earthquake and tsunami catalogues are known to be incomplete (Hadler et al. 2012, Papadopoulos 2015: 150). Based on original grain size data, we show that the sediment core from the central harbour basin drilled by Morhange et al. (2012) includes two tsunami candidate layers so far unrecognized. Moreover, the re-interpretation of vibracore data from Hadler et al. (2013) by Kolaiti et al. (2017) in terms of man-made intervention instead of tsunami-related impact is not consistent with available macro- and microfossil signatures. In order to achieve a consistent set of comparable radiocarbon data, we calculated the best-fit approximation of the local marine reservoir effect (MRE) for the Lechaion area as ΔR = 133 ± 75 for marine samples and used this new ΔR to re-calibrate all available radiocarbon ages published by Stiros et al. (1996), Morhange et al. (2012), Campos et al. (2013a, 2013b) and Hadler et al. (2013). Bringing together ancient harbour chrono-stratigraphies and the seismo-tectonic history of Lechaion and its environs, the timing of tsunami event I identified by Hadler et al. (2013) can be refined to the 770s cal BC, i.e. the early 8th cent. BC. This age is well consistent with the age of a homogenite-turbidite sequence described by Campos et al. (2013a, 2013b) from c. 42 km distant from Lechaion at 867 m water depth indicating an earthquake-triggered tsunami/seiche effect. The age of tsunami event II detected at Lechaion by Hadler et al. (2013) can now be specified more precisely, namely to c. 44 cal BC – 73 cal AD. This age is in close agreement with the age of an older tsunami candidate layer discovered in the core from Morhange et al. (2012) dated to the time before 88–215 cal AD (terminus ante quem). These results cover the time period for which historical sources report on a strong earthquake that caused widespread damage to Corinth’s infrastructure in AD 74, AD 77 or between AD 69–79 (Mourtzas et al. 2014). We therefore suggest that the Lechaion vibracore transect and core 1 drilled by Morhange et al. (2012) give joint evidence of this major earthquake and associated tsunami impact between AD 69–79. Moreover, the uplift of the ancient harbour at Lechaion most probably occurred co-seismically in connection with the same earthquake and not hundreds of years earlier as thought before. This historical earthquake seems to have also caused severe surface deformation structures at Lechaion. Concerning geoarchaeological aspects, this paper upholds the idea that the early Christian basilica at Lechaion was originally standing on even ground and not partly entrenched into thick local sands and gravels, as suggested by Kolaiti et al. (2017). Palaeoseismological studies by Minos-Minopoulos et al. (2015) underline the initial assessment by Hadler et al. (2013) that the AD 551/552 earthquake and associated earthquake-triggered effects severely damaged the basilica (although historical accounts do not exist) and initiated ongoing disintegration of the remaining ruins. Co-seismic uplift at the Perachora Peninsula as indicated by geomorphological evidence is dated to the same period (Pirazzoli et al. 1994). This abrupt crust-uplift is a plausible trigger for the strong earthquake and local tsunami that hit both Lechaion and the diolkos area in the 6th cent. AD. This contribution also deals with an ideology-driven non-catastrophist trend that comes alight in the paper of Kolaiti et al. (2017). This trend is directed against a so-called neo-catastrophist paradigm and seeks to talk down the impact of seismo-tectonic events in the Mediterranean. We use this case study to show that the solid interpretation of geoscientific facts allows a much more differentiated picture of the reality as the simplistic one painted by Kolaiti et al. (2017). Based on our results, it is recommended not to underestimate the local to regional earthquake and tsunami hazard for the eastern Gulf of Corinth region, even if major impacts have a recurrence interval of several hundreds of years.
Keywords
Palaeotsunami • ancient harbor • beachrock • Gulf of Corinth • Lechaion