Geological Society of America

T108 Integrated Detrital Records of Orogenic Systems (Posters)

Monday, 5 November 2012
9:00 AM - 6:00 PM
Hall B

A ~ 604 MA DEPOSITIONAL AGE FOR THE TIDDILINE CONGLOMERATE, BOU AZZER INLIER, MOROCCO BASED ON U-PB DATING OF DETRITAL ZIRCON

Paper number: T108-12
Program: Technical Sessions
Time: 9:00 AM – 6:00 PM

Authors

Kevin Hefferan Presenting Author
University of Wisconsin-Stevens Point, Stevens Point, WI
Scott Samson
Syracuse University, Syracuse, NY
Jack Hietpas
Syracuse University, Syracuse, NY
Hassan Admou
Faculty of Sciences Semlalia, Cadi Ayyad University, Marrakech, N/A
Jeremy Inglis
University of North Carolina-Chapel Hill, Chapel Hill, NC
Ali Saquaque
Marrakech, N/A
Neil Heywood
University of Wisconsin-Stevens Point, Stevens Point, WI

Abstract

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 (N30^o 25.083396’, W 6^o 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 30^o31.476474’, W 6^o 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.