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with 18 fi gures and 2 tables Summary. Th is paper presents geo-scientifi c evidence of beachrock-type calcarenitic tsunamites from three study areas in western Greece, namely from the Bays of Aghios Nikolaos (Akarnania), Langadakia (Cefalonia Island) and Aghios Andreas (Peloponnese). Geomorphological, sedimentological, micromorphological and geochemical studies were conducted to clarify depositional processes and the post-sedimentary evolution. Calcarenitic and locally conglomeratic carbonate crusts were studied in natural outcrops along the seafront and in vibracores. High-resolution topographic surveys and 3D-visualisation were carried out by diff erential GPS and LIDAR measurements. Tsunami impact was dated by a combined approach of radiocarbon, OSL and archaeological age determination and compared to local tsunami and earthquake chronologies. We found sedimentary structures such as basal unconformities, rip-up and intra-clasts, evidence of fi ning upward, thinning landward and upward increase in sorting as well as bi-to multimodal deposits and injection structures all of which are described as features typical of recent or historic tsunami deposits. Typically non-littoral sedimentary features such as load casts and convolute bedding further indicate gravity driven processes in water-saturated sheets of allochthonous deposits and are well known from, for example, turbidites. Moreover, thin section analyses revealed highenergy shock-and impact-borne cracking and shearing eff ects. Our results show that cementation of tsunami deposits may occur by post-depositional pedogenetic decalcifi cation of higher sections and subsequent secondary carbonate precipitation in lower sections of tsunami deposits provided that they were deposited above sea level. Th e calcarenitic tsunamites encountered in the three study areas match the defi nition of beachrock sensu stricto. Th is is thus the fi rst paper giving examples of beachrock sequences that are interpreted as partially cemented tsunami deposits. Consequently, beachrock is recommended not to be used as sea level indicator in future studies unless a tsunamigenic formation can be defi nitely excluded. Dating results brought to light young, mostly Holocene ages of tsunami sediments. In the Bay of Aghios Andreas, western Peloponnese, we found spectacular traces that Olympia's ancient harbour site Pheia was destroyed by tsunami impact in the 6 th cent. AD and covered by a rapidly cemented, up to 3 m-thick beachrock-type tsunami deposit. Zusammenfassung. Dieser Aufsatz stellt geowissenschaftliche Belege für Beachrock-artige kalkarenitische Tsunamite aus drei Untersuchungsgebieten Westgriechenlands vor, nämlich der Bucht von Aghios Nikolaos (Akarnanien), der Bucht von Langadakia (Kephallonia) und der Bucht von Aghios Andreas (Peloponnes). Geomorphologische, sedimentologische, mikromorphologische und geochemische Analysen dienten der Klärung von Ablagerungsprozessen und der postsedimentären Entwicklung. Kalkarenitische und lokal konglomeratische Karbonatkrusten wurden in natü...

Aims In minimally invasive surgery (MIS), intraoperative guidance has been limited to verbal communication without direct visual guidance. Communication issues and mistaken instructions in training procedures can hinder correct identification of anatomical structures on the MIS screen. The iSurgeon system was developed to provide visual guidance in the operating room by telestration with augmented reality (AR). Methods Laparoscopic novices (n = 60) were randomized in two groups in a cross-over design: group 1 trained only with verbal guidance first and then with additional telestration with AR on the operative screen and vice versa for group 2. Training consisted of laparoscopic basic training and subsequently a specifically designed training course, including a porcine laparoscopic cholecystectomy (LC). Outcome included time needed for training, performance with Global Operative Assessment of Laparoscopic Skills (GOALS), and Objective Structured Assessment of Technical Skills (OSATS) score for LC, complications, and subjective workload (NASA-TLX questionnaire). Results Telestration with AR led to significantly faster total training time (1163 ± 275 vs. 1658 ± 375 s, p < 0.001) and reduced error rates. LC on a porcine liver was performed significantly better (GOALS 21 ± 5 vs. 18 ± 4, p < 0.007 and OSATS 67 ± 11 vs. 61 ± 8, p < 0.015) and with less complications (13.3% vs. 40%, p < 0.020) with AR. Subjective workload and stress were significantly reduced during training with AR (33.6 ± 12.0 vs. 30.6 ± 12.9, p < 0.022). Conclusion Telestration with AR improves training success and safety in MIS. The next step will be the clinical application of telestration with AR and the development of a mobile version for remote guidance.