by Anneleen Foubert, Tesfaye Kidane, Derek Keir

Since the early days of the continental drift theory, the Afar triangle developed into an ideal field laboratory where the onset of continental and potentially future oceanic rifting can be studied in detail. The Danakil Depression is the northern portion of the Afar triangle, bordered to the west by the Nubian Plateau and to the East by the Danakil Horst, and characterized by active rifting since Oligocene times. This ADD-ON workshop proposal requests funding for the organization of a workshop bringing together junior and senior scientists from different disciplines to fine-tune common scientific goals, specify drilling targets and discuss technical and logistical issues in this extra-ordinary field lab to develop an integrated full ICDP proposal. The overarching scientific goal is to get insights into the detailed sedimentary facies evolution in an active rift setting paced by global environmental fluctuations and their interplay with volcano-tectonic events. Seismo-stratigraphic interpretations based on industrial seismic sections, core and borehole data evidence the presence of Pleistocene evaporite units until the depth of about 900 m below the Dallol salt pan (central Danakal Depression, northern Afar). However, to date not any sub-salt sedimentary core records are available from the central part of the rift basin filled with more than 5 km of sediments. Having future access to targeted drilling sites in the Danakil basin will give new insights into (1) the mechanical understanding of intermittent and incipient basin dynamics in an initial extensive continental rift basin: from rifting towards the development of passive margins, (2) East African climatic changes and Hominin evolution, (3) the limits of the deep biosphere in extreme hypersaline and high-temperature environments below the salt deposits, (4) natural fluid flow in an active geothermal system and (5) monitoring of active faults, earthquakes and volcanic events in remote areas. Besides fine-tuning drilling objectives and technical discussions, the ADD-ON workshop aims to provide a discussion platform between industry, stakeholders and scientists to identify how drilling can help in resolving urgent societal needs in remote areas often suffering from extreme natural hazards. Deep scientific drilling in the Afar will be necessary in the rapid assessment of geothermal potential, the quest for ground water resources and advanced Potash exploitation.

• For the ADD-ON project, we have identified the following scientific objectives which closely relates to the goals identified in the ICDP Science Plan and should be further fine-tuned during the ADD-ON Workshop:
• (1) Understanding intermittent and incipient dynamics in an extensional rift basin: from continental rift towards young ocean basin and passive margin development?
• (2) Unique and continuous sedimentary and stratigraphic reference record to constrain (1) East African Climate Change going beyond 250 ka and understanding its impact on (2) East African Hominin Evolution.
• (3) Understanding the limits of the deep biosphere in extreme hypersaline environments.
• (4) Understanding and characterization of active high-enthalpy geothermal systems.
• (5) Downhole Earth Observatory: monitoring of active faults, earthquakes and volcanism

Basin Dynamics, Deep Biosphere, Paleoclimate, Paleoenvironment, Passive Margins, Rifting, Seismicity

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