The Dra or Draa Valley is a main valley running over a
    distance of almost 600 km in parallel to the overall strike
    direction of the Anti-Atlas Palaeozoic, from about Zagora
    in the NE to Tan-Tan near the Atlantic Ocean in the SW.
    From Zagora a significant branch of the valley cuts in
    northwestern direction through the Palaeozoic and
    Precambrian   towards Ouarzazate, creating spectacular
    outcrops. The main Oued Dra runs over wide distance in
    parallel to   the topmost Devonian and prominent
    Toumaisian Jebel Tazout, mostly very close to the
    Moroccan-Algerian border, and partly has become
    inaccessible for security reasons.  However, the Dra Valley
    has given its name to the wide stretch of Devonian outcrops
    (HOLLARD & JAQUEMONT 1956, HOLLAPD 1978) which
    forms the northern limb of the extensive Tindouf Basin.
    This stretches into former Spanish Sahara and
    northern Mauritania in the SW (forming the Zemmour as an
    appendix) and into large parts of Algeria in its southern,
    central and eastern parts, including the poorly studied
    Menakeb in the SE.