Paper No. 12
Presentation Time: 9:00 AM-6:00 PM


HEFFERAN, Kevin1, SAMSON, Scott2, HIETPAS, Jack3, ADMOU Sr, Hassan4, INGLIS, Jeremy5, SAQUAQUE, Ali6 and HEYWOOD, Neil1, (1)Geography and Geology, University of Wisconsin-Stevens Point, Stevens Point, WI 54481, (2)Department of Earth Sciences, Syracuse University, 204 Heroy Geology Laboratory, Syracuse, NY 13244, (3)Department of Earth Sciences, Syracuse University, 204 Heroy Laboratory, Syracuse, NY 13244, (4)Department of Geology, Faculty of Sciences Semlalia, Cadi Ayyad University, Boulevard Prince My Abdellah, B.P. 2390 MAROC, Marrakech, 40005, Morocco, (5)Isotope Geochemistry/Geochronology Lab, University of North Carolina-Chapel Hill, Department of Geological Sciences, Chapel Hill, NC 27516, (6)Reminex Mining, Marrakech, Morocco,

Sedimentary basins provide critical constraints on orogenesis in convergent margin settings. This study analyzes for the first time detrital zircon ages obtained from Tiddiline Formation clasts collected from a Neoproterozoic synorogenic basin in Bou Azzer, Morocco. The Northern Tiddiline clastic basin, located adjacent to the Bou Azzer ophiolite, contains folded coarsening upwards assemblages marking the late stages of the Pan African orogenic cycle in North Africa. The Tiddiline Formation consists of five stratigraphic components, which are from oldest to youngest: a basal hematitic siltstone overlain by a hematitic sandstone and conglomerate; arkosic sandstone and quartz arenite represent the upper two units. Since 2000, debate concerning the stratigraphic placement of the Tiddiline Formation has centered on whether these rocks belong to the Saghro Group (~630-610 Ma), Bou Salda Group (~610-580) or Ouarzazate Group (575-540 Ma)—all of which are exposed in a series of erosional inliers exposing Proterozoic orogenic sequences within the Anti-Atlas Mountains.

To address this debate, U-Pb ages of detrital zircon crystals were determined using the UCLA CAMECA 1270 ion microprobe. Folded beds of the Tiddiline conglomerate collected east of Ait Ahmane (Bou Azzer) in the Northern Tiddiline Basin (N30o 25.083396’, W 6o 28.187513’) of Bou Azzer contain detrital zircon yielding an age of 604 +/- 18 Ma, suggesting correlation with the Bou Salda Group rocks exposed in adjacent erosional inliers.

Quartz phyric volcanic rocks (N 30o31.476474’, W 6o 42.234728’) exposed in the northern Tiddiline basin and historically associated with the Tiddiline Formation, have been dated at 639 +/- 24 Ma. Rather than related to the late orogenic clastic basin deposits, the quartz phyric volcanic rocks are now recognized as being synchronous with the adjacent synorogenic Ousdrat quartz diorite intrusion (640.8 +/- 1.4 Ma). Available geochronologic evidence suggests that the Tiddiline Formation developed in the waning stages of a Pan African collision between a volcanic arc terrane and the West African craton ~585-620 Ma, in the aftermath of subduction generated arc magmatism and metamorphism ~640-650 Ma. This collision marked the final assembly stage of the Western Gondwana Supercontinent.