Geologic Map of the Northern Harrat Rahat Volcanic Field, Kingdom of Saudi Arabia By Drew T. Downs, Joel E. Robinson, Mark E. Stelten, Duane E. Champion, Hannah R. Dietterich, Thomas W. Sisson, Hani Zahran, Khalid Hassan, and Jamal Shawali Pamphlet to accompany U.S. Geological Survey Scientific Investigations Map 3428 Saudi Geological Survey Special Report SGS–SP–2019–2 2019 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior DAVID BERNHARDT, Secretary U.S. Geological Survey James F. Reilly II, Director U.S. Geological Survey, Reston, Virginia: 2019 For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment—visit https://www.usgs.gov or call 1–888–ASK–USGS. For an overview of USGS information products, including maps, imagery, and publications, visit https://store.usgs.gov. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner. Suggested citation: Downs, D.T., Robinson, J.E., Stelten, M.E., Champion, D.E., Dietterich, H.R., Sisson, T.W., Zahran, H., Hassan, K., and Shawali, J., 2019, Geologic map of the northern Harrat Rahat volcanic field, Kingdom of Saudi Arabia: U.S. Geological Survey Scientific Investigations Map 3428 [also released as Saudi Geological Survey Special Report SGS–SP–2019–2], 65 p., 4 sheets, scales 1:75,000, 1:25,000, https://doi.org/10.3133/sim3428. Associated data for this publication: Robinson, J.E., Downs, D.T., Stelten, M.E., Champion, D.E., Dietterich, H.R., Sisson, T.W., Zahran, H., Hassan, K., and Shawali, J., 2019, Database for the geologic map of the northern Harrat Rahat volcanic field, Kingdom of Saudi Arabia: U.S. Geological Survey data release, https://doi.org/10.5066/P9Q3WGTN. ISSN 2329-1311 (print) ISSN 2329-132X (online) ISBN 978-1-4113-4291-0 Cover. Aerial view to southeast along domes, craters, and pyroclastic flow deposits in Al Efairia area of northern Harrat Rahat volcanic field, Kingdom of Saudi Arabia. Photograph by Andrew Calvert, 2014. Ministry of Industry and Mineral Resources BANDAR ALKHORAYEF, Minister Saudi Geological Survey Khalid bin Saleh Al-Mudaifer, President Saudi Geological Survey, Jeddah, Kingdom of Saudi Arabia: 2019 Contents Introduction.....................................................................................................................................................1 Physiography and Access ...................................................................................................................1 Previous Work .......................................................................................................................................6 Methods..................................................................................................................................................7 Geologic and Tectonic Setting .....................................................................................................................8 Harrat Rahat Volcanic Field .........................................................................................................................8 Compositions and Eruptive Styles of Volcanic Rocks ............................................................................10 Petrographic Characteristics of Volcanic Rocks ...................................................................................11 Eruptive History of Northern Harrat Rahat and its Environs .................................................................12 Tertiary Volcanic Rocks .....................................................................................................................13 Volcanic Rocks of Harrat Kurama ....................................................................................................13 Volcanic Rocks of Northern Harrat Rahat .....................................................................................13 Eruptive Stage 12 (1,200 to 780 ka) ..........................................................................................13 Eruptive Stage 11 (780 to 570 ka) .............................................................................................15 Eruptive Stage 10 (570 to 460 ka) .............................................................................................15 Eruptive Stage 9 (460 to 360 ka) ...............................................................................................15 Eruptive Stage 8 (360 to 323 ka) ...............................................................................................16 Eruptive Stage 7 (323 to 260 ka) ...............................................................................................16 Eruptive Stage 6 (260 to 180 ka) ...............................................................................................16 Eruptive Stage 5 (180 to 100 ka) ...............................................................................................16 Eruptive Stage 4 (100 to 70 ka) .................................................................................................17 Eruptive Stage 3 (70 to 45 ka) ...................................................................................................17 Eruptive Stage 2 (45 to 11 ka) ...................................................................................................17 Eruptive Stage 1 (11 to 0 ka) .....................................................................................................18 Acknowledgments .......................................................................................................................................18 Description of Map Units ............................................................................................................................18 Surficial Deposits ................................................................................................................................18 Quaternary Volcanic Rocks ...............................................................................................................18 Volcanic Rocks of Northern Harrat Rahat .............................................................................19 Eruptive Stage 1 (0 to 11 ka) ............................................................................................19 Eruptive Stage 2 (11 to 45 ka) ..........................................................................................19 Eruptive Stage 3 (45 to 70 ka) ..........................................................................................20 Eruptive Stage 4 (70 to 100 ka) ........................................................................................21 Eruptive Stage 5 (100 to 180 ka) ......................................................................................22 Eruptive Stage 6 (180 to 260 ka) ......................................................................................26 Eruptive Stage 7 (260 to 323 ka) ......................................................................................31 Eruptive Stage 8 (323 to 360 ka) ......................................................................................33 Eruptive Stage 9 (360 to 460 ka) ......................................................................................33 Eruptive Stage 10 (460 to 570 ka) ....................................................................................37 Eruptive Stage 11 (570 to 780 ka) ....................................................................................40 Eruptive Stage 12 (780 to 1,200 ka) .................................................................................41 Volcanic Rocks of Harrat Kurama ...........................................................................................41 Tertiary Volcanic Rocks .....................................................................................................................41 Precambrian Rocks ............................................................................................................................42 References Cited..........................................................................................................................................42 v Figures 1. Map showing tectonic setting of Harrat Rahat volcanic field, as well as locations of continental, intraplate volcanic fields encompassed by Arabian plate .........................2 2. Colored shaded-relief map of Harrat Rahat volcanic field .....................................................3 3. Shaded-relief map of northern Harrat Rahat volcanic field, showing distribution of volcanic-rock units and other units shown on sheet 1. Figure is on sheet 4; caption included here for continuity .........................................................................sheet 4 4. Plots showing analyses of 661 volcanic rocks from northern Harrat Rahat volcanic field ..........................................................................................................................................4 5. Shaded-relief map of northern Harrat Rahat volcanic field, showing compositions of eruptive products. Also shown are locations of vents and approximate locations and trends of vent axes ..........................................................................................................5