Geology Reference
In-Depth Information
Fig. 8
Examples of stratigraphy
and sedimentary features in strata
of Proterozoic to Devonian age in
the Anti-Atlas.
a
Kess Kess mud
mound.
b
Hill-capping Devonian
coral-stromatoporoid biostrome
limestone.
c
Close-up of coral-
stromatoporoid biostrome
limestone.
d
Outcrop of
Orthoceras-bearing limestone.
e
Close-up of
Orthoceras
-bearing
limestone showing current-
oriented
Orthoceras
.
f
Stratiform
sheets of Cambrian sandstone and
shale.
g
Sand dykes in Cambrian
sandstone and shale sequence.
h
Horizontal
and
vertical
burrows
in Devonian Goniatite-bearing
limestone.
i
Lamination in
Proterozoic stromatolites (vertical
section)
5.1.4 Neoproterozoic Passive Margin Series
(Taghdout Group) with Its Well-Preserved
Sedimentary Features (ca 800 Ma) and Its
Pre-Pan-African Doleritic Sills
Neoproterozoic (ca 800 Ma) volcano-sedimentary sequences
of the northern rifted margin of the WAC are exposed in the
central and western Anti-Atlas inliers. The Zenaga Eburnian
gneisses are overlain in their northern edge by Neoprotero-
zoic quartzite and carbonate rocks with interbedded conti-
nental tholeiitic basaltic lavas. These sedimentary rocks are
micropegmatite, hornblende and biotite. The secondary
mineralogy includes albite, chlorite, actinolite, epidote,
sphene, calcite and quartz. These doleritic dykes are occa-
sionally deformed where they are intersected by mylonite.
These basic rocks are also interbedded in the sedimentary
passive margin series. Similar basic rocks were de
ned in
the western Anti-Atlas inliers (Iguerda, Tagragra d
'
Akka,
Bas Dr
a, Ighrem and Kerdous) and are described as witness
of the break-up of the WAC during the Pre-Pan-African
orogeny around 1,000
à
800 Ma.
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