TY - JOUR
T1 - Saqqar
T2 - A 34 km diameter impact structure in Saudi Arabia
AU - Kenkmann, Thomas
AU - Afifi, Abdulkader M.
AU - Stewart, Simon A.
AU - Poelchau, Michael H.
AU - Cook, Douglas J.
AU - Neville, Allen S.
PY - 2015/11/1
Y1 - 2015/11/1
N2 - Here we present the first proof of an impact origin for the Saqqar circular structure in northwestern Saudi Arabia (Neville et al.), with an apparent diameter of 34 km, centered at 29°35′N, 38°42′E. The structure is formed in Cambrian-Devonian siliciclastics and is unconformably overlain by undeformed Cretaceous and Paleogene sediments. The age of impact is not well constrained and lies somewhere between 410 and 70 Ma. The subsurface structure is constrained by 2-D reflection seismic profiles and six drilled wells. First-order structural features are a central uplift that rises approximately 2 km above regional datums, surrounded by a ring syncline. The crater rim is defined by circumferential normal faults. The central uplift and ring syncline correspond to a Bouguer gravity high and an annular ring-like low, respectively. The wells were drilled within the central uplift, the deepest among them exceed 2 km depth. Sandstone core samples from these wells show abundant indicators of a shock metamorphic overprint. Planar deformation features (PDFs) were measured with orientations along (0001), {1013}, and less frequently along {1011} and {1014}. Planar fractures (PFs) predominantly occur along (0001) and {1011}, and are locally associated with feather features (FFs). In addition, some shocked feldspar grains and strongly deformed mica flakes were found. The recorded shock pressure ranges between 5 and 15 GPa. The preserved level of shock and the absence of an allochthonous crater fill suggest that Saqqar was eroded by 1-2 km between the Devonian and Maastrichtian. The documentation of unequivocal shock features proves the formation of the Saqqar structure by a hypervelocity impact event.
AB - Here we present the first proof of an impact origin for the Saqqar circular structure in northwestern Saudi Arabia (Neville et al.), with an apparent diameter of 34 km, centered at 29°35′N, 38°42′E. The structure is formed in Cambrian-Devonian siliciclastics and is unconformably overlain by undeformed Cretaceous and Paleogene sediments. The age of impact is not well constrained and lies somewhere between 410 and 70 Ma. The subsurface structure is constrained by 2-D reflection seismic profiles and six drilled wells. First-order structural features are a central uplift that rises approximately 2 km above regional datums, surrounded by a ring syncline. The crater rim is defined by circumferential normal faults. The central uplift and ring syncline correspond to a Bouguer gravity high and an annular ring-like low, respectively. The wells were drilled within the central uplift, the deepest among them exceed 2 km depth. Sandstone core samples from these wells show abundant indicators of a shock metamorphic overprint. Planar deformation features (PDFs) were measured with orientations along (0001), {1013}, and less frequently along {1011} and {1014}. Planar fractures (PFs) predominantly occur along (0001) and {1011}, and are locally associated with feather features (FFs). In addition, some shocked feldspar grains and strongly deformed mica flakes were found. The recorded shock pressure ranges between 5 and 15 GPa. The preserved level of shock and the absence of an allochthonous crater fill suggest that Saqqar was eroded by 1-2 km between the Devonian and Maastrichtian. The documentation of unequivocal shock features proves the formation of the Saqqar structure by a hypervelocity impact event.
UR - http://www.scopus.com/inward/record.url?scp=84946094282&partnerID=8YFLogxK
U2 - 10.1111/maps.12555
DO - 10.1111/maps.12555
M3 - Article
AN - SCOPUS:84946094282
VL - 50
SP - 1925
EP - 1940
JO - Meteoritics and Planetary Science
JF - Meteoritics and Planetary Science
SN - 1086-9379
IS - 11
ER -