Geology and Archaeology of the late 4th century CE Earthquake-Tsunami event that struck the ancient roman city of Baelo Claudia (Cádiz, South Spain)

• Main Authors: Silva Barroso, Pablo Gabriel, Reicherter, Klaus, García-Jiménez, Iván, Prados-Martínez, Fernando, Pérez-Tarruella, Javier, Sánchez-Sánchez, Yolanda
• Format: Article in Journal/Newspaper
• Language: Spanish
• Published: Cuaternario y Geomorfología 2023
• Subjects: Archaeoseismology; Earthquake Archaeological Effects (EAEs); Tsunamite; Baelo Claudia; Gibraltar Strait; South Spain; Arqueosismología; Efectos Arqueológicos de los Terremotos (EAEs); Tsunamita; Estrecho de Gibraltar; Sur de España; Estrecho; Planktonic foraminifera
• Online Access: https://recyt.fecyt.es/index.php/CUGEO/article/view/102693

This paper summarizes the set of new geological and archaeological studies that certify the occurrence of a powerful earthquake-tsunami event that devastated the ancient Roman city of Baelo Claudia (Strait of Gibraltar) in the second half of the 4th century AD. Apart from the important coseismic deformations documented in the in the architectural remains (EAEs), the present study focuses on the effects and sedimentary record of the subsequent tsunami. Analysis of tsunami deposits in drill cores and outcrops along the lower part of the city indicate that the tsunami reached a minimum height of + 8m above sea level and penetrated at least 250 m inland reaching the base of the temples above the Forum area. However, in the small creeks around the area and in the ancient eastern littoral lagoon, flooding could have penetrated up to about one kilometre. The tsunami layer is a dark cohesive sandy deposit (28 to 52 cm thick) containing fragments of pottery, fish and animal bones, glassware, bricks and large boulders of masonry blocks and column drums. The layer also contains microfaunal assemblages with a mixture of benthic and planktonic foraminifera as well as lagoonal brackish-water gastropods and numerous shell debris and broken reworked foraminifera. Data presented in this work indicate that the tsunami layer is mainly composed of well-rounded fine-medium sands originating from the reworking of aeolian and littoral beach deposits of the old roman spit-bar enclosing the ancient embayment. We interpret most of the tsunami layer as backwash deposits trapped within the ruins of the city after the earthquake destruction, as testified by recent excavations along de decumanus maximum, Termas Marítimas and the funerary mausoleum of Iunia Rufina in the eastern necropolis. The archaeological findings in this funerary monument toppled by the earthquake and the subsequent tsunami allow to establish the age of this event between 350 - 390 AD. Key words: Archaeoseismology, Earthquake Archaeological Effects (EAEs), Tsunamite, ...