Coastal boulders as evidence for high-energy waves on the Iranian coast of Makran

Majid Shah-hosseini, Christophe Morhange, Abdolmajid Naderi Beni, Nick Marriner, Hamid Lahijani, Mohammadali Hamzeh, François Sabatier

Research output: Contribution to journalArticlepeer-review

Abstract

Coastal boulder deposits attesting to large waves are found along the rocky coast of Makran (Iran) from Chabahar to Lipar. Boulders are either scattered on the rocky coastal platform or accumulated in imbricated clusters. The boulders are mostly rectangular and composed of biogenic calcarenite deriving from the present coastal platform. Significant morphological features observed on the boulders include supratidal karstic pools, sharp broken edges and fractures. Some boulders contain boreholes and shells of marine bivalves, suggesting detachment and transportation from the subtidal zone. The dimensions, elevation and distance from the coastline of 58 representative boulders are documented to estimate their volume, weight and inland displacement. The boulders, weighing up to 18. t, are found up to 6. m above present mean sea level and up to 40. m from the present shoreline. We applied hydrological models to estimate and compare the wave height and inundation distance required to transport the boulders inland. Our results demonstrate that no known or probable storm event on the Makran coast is capable of detaching and transporting the boulders. In contrast, tsunami wave height of 4. m is enough to detach all the boulders from the rocky coast and transport them inland. We conclude that a tsunamigenic origin for boulder deposits is most plausible. Our results imply that the western part of the Makran coast has archived evidence of paleotsunami events, probably generated by large earthquakes at the Makran subduction zone.

Original languageEnglish
Pages (from-to)17-28
Number of pages12
JournalMarine Geology
Volume290
Issue number1-4
DOIs
StatePublished - 1 Dec 2011
Externally publishedYes

Bibliographical note

Funding Information:
This study is a result of cooperation between European center of geoscience and environmental researches (CEREGE) and Iranian national institute for oceanography (INIO) and was financially supported by the Franco–Iranian research program of PHC Gundishapur (project no. 23178UD ) offered by Egide, French Ministry of Foreign and European Affairs and Iranian Center for International Scientific Studies and collaborations (CISSC) . Radiocarbon dating was supported by ARTEMIS INSU. We wish to thank Brian Atwater, Giuseppe Mastronuzzi, Dieter Kelletat and an anonymous reviewer for their constructive comments.

Keywords

  • Boulder
  • Coast
  • Gulf of Oman
  • Hazard
  • Inundation
  • Iran
  • Makran
  • Storm
  • Tsunami

ASJC Scopus subject areas

  • Oceanography
  • Geology
  • Geochemistry and Petrology

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