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Homogenites - Unifites

Quaternary Volcanic Eruptions of the Santorini Island and Associated Gravity Flow Deposits in the Cretan Basin, South Aegean Sea. Efthymios K. Tripsanas, Aristomenis P. Karageorgis, Christos Anagnostou, Vasilis Lykousis, Dimitris Sakelariou

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Homogenites - Unifites

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  1. Quaternary Volcanic Eruptions of the Santorini Island and AssociatedGravity Flow Deposits in the Cretan Basin, South Aegean Sea Efthymios K. Tripsanas, Aristomenis P. Karageorgis, Christos Anagnostou, Vasilis Lykousis, Dimitris Sakelariou Hellenic Centre for Marine Research, Institute of Oceanography Anavyssos, Greece, etripsan@ath.hcmr.gr

  2. Characteristics • Homogenous mud deposits (optical observations and X-ray radiographs) • Usually based by a thick (up to 0.5 m), massive to laminated sand layer • Couple of meters to several decameters thick • Transparent seismic packets that smooth out all existing morphology • Occurrence • Confined basins • Genessis • Related to catastrophic events, such as large sediment failures caused by earthquakes • Process • Segregation of high-energy turbidity currents (Cita and Aloisi, 2000) • Reflection of a high-energy turbidity current on the walls of a confined deep-water basin, with progressive confinement (Tripsanas et al., 2004) • An oscillatory movement of the whole water mass, initiated by a sudden bottom modification (sieche effect) (Beck et al., 2007) Homogenites - Unifites

  3. Example of Homogenites from the Gulf of Mexico 1.5 m Tripsanas et al., 2004

  4. Santorini CRETE Cretan Basin

  5. Thick Deposits of Homogenites These deposits have related to the Minoan volcanic eruption at 3.6 ka Are we sure about that? Several sand beds on top of the homogenites, and lack of a distinct and clear radiocarbon date Anastasakis (2008)

  6. Volcanic eruptions of Santorini Island Caldera Collapse 4 Caldera Collapse 3 Caldera Collapse 2 Caldera Collapse 1 Heiken and McCoy (1984), Druitt et al. (1989)

  7. Pliocene/Quaternary Pyroclastic Flows Debris flows? Messinian N S Pathways of Pyroclastic and Gravity Flows 1.2 km 100 ms or 75 m

  8. N S Pathways of Pyroclastic and gravity Flows 1.2 km 100 ms or 75 m

  9. W E 1.2 km Pathway for Santorini Pyroclastic Flows? Pathways of Pyroclastic and Flows 100 ms or 75 m

  10. W E Deep Basin Deposits - Homogenites 1.2 km 100 ms or 75 m

  11. Which volcanic eruptions resulted in these gravity flows? AEG-02 AEG-03

  12. Ash Layers in Cretan Basin Y4 ash layer ~30-40 ka Z2 ash layer ~3.6 ka Y2 ash layer ~20 ka

  13. ? Age Determination - Homogenites Z2 ash layer ~3.6 ka Y4 ash layer ~30-40 ka Y2 ash layer ~20 ka

  14. Age Determination - Homogenites Z2 glass turbidite ~3.6 ka Z2 glass turbidite ~3.6 ka Y2 glass turbidite ~20 ka Y2 glass turbidite ~20 ka Homogenites Homogenites Homogenites Y4 glass turbidite ~30-40 ka Homogenites Homogenites 22 13

  15. Volcanic eruptions of Santorini Island Caldera Collapse 4 Caldera Collapse 3 Caldera Collapse 2 Caldera Collapse 1 Heiken and McCoy (1984), Druitt et al. (1989)

  16. The homogenites formed shortly before the Y-4 ash layer, and probably was the Upper Scoriae 2 eruption phase that resulted in their formation • The thick uniform mud deposits in the homogenites require a process that would be able to erode, suspend, and transfer vast amounts of mud from the shelf and slope to the deep Cretan Basin • Origin • The production of large gravity flows, originating from the collapse of the dome • And/or • Underwater propagating pyroclastic flows have been observed in other areas (e.g. Soufriere Hills volcano, Montserrat, West Indies by Trofimovs et al., 2008) • The absence of uniform, thick mud deposits on top of the thin sand turbidites of the Minoan (Z2) and Cape Riva (Y2) volcanic eruptions suggests a different origin for their formation, most likely post-generated small-scale landslide events related to regional earthquakes Discussion

  17. Discussion • Homogenites in Cretan Basin are related to catastrophic volcanic eruptions • Not all volcanic eruptions produce homogenites • Homogenites do not provide a full record of volcanic activity, but only of the most major eruptions

  18. The Minoan Eruption at 3.6 ka resulted in the destruction of civilization, and is mentioned by many people as a disaster of biblical proportions THIS ERUTION WAS NOT ONE OF THE LARGEST!!! What if a homogenite producing eruption is going to occur in the near future? Question - Statement Thank you

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