Ja. Millson et al., THE LOWER PALEOZOIC OF OMAN AND ITS CONTEXT IN THE EVOLUTION OF A GONDWANAN CONTINENTAL-MARGIN, Journal of the Geological Society, 153, 1996, pp. 213-230
The Lower Palaeozoic Haima Group of the Sultanate of Oman comprises a
sequence dominated by siliciclastic rocks up to several kilometres thi
ck and broadly divisible into two groups. The sequence is known in out
line from subsurface exploration, but recent field work on outcrops in
the isolated Huqf area in east-central Oman has allowed a more detail
ed environmental interpretation of the succession. At the base coarse
continental deposits of the Lower Haima Group rest unconformably on Pr
ecambrian-Lower Cambrian Huqf Group sediments (mainly carbonates and e
vaporites). The overlying Upper Haima Group comprises from base to top
the aeolian dominated Amin Formation, the non-marine (coastal plain)
to shallow marine (intertidal-subtidal) sediments of the Andam Formati
on, the non-marine to marginally marine Ghudun Formation, and the comp
lex cyclical deep to shallow water deposits of the Safiq Formation. Co
rrelation of the Haima Group of Oman with the Lower Palaeozoic of the
Arabian Peninsula, North Africa and Iran allows the evolution of the G
ondwanan margin to be modelled. A widespread Lower Cambrian sequence o
f coarse alluvium, resting on peneplained Upper Precambrian-Infracambr
ian Huqf Group strata, represents the final stage of uplift and basin
fill associated with the Late Proterozoic suturing of Arabia and adjac
ent plates which resulted in the formation of the Gondwanan continent.
The overlying thick sequence of continental (fluvial and aeolian) sed
iments was deposited in a series of stable intracratonic basins across
the Gondwanan landmass. In the Mid- and Late Cambrian an overall sea-
level rise led to the repeated development of shallow marine shelf car
bonates across the margin. The subsequent replacement of this marginal
carbonate sequence with a thick marginal to non-marine, sand dominate
d sequence may reflect the interplay of several events: the drift of G
ondwana towards more southerly latitudes, a phase of strong tectonic r
ejuvenation during the latest Cambrian-Early Ordovician, and/or a eust
atic fall in sea-level. Organic-rich marine mudrocks were deposited ov
er much of the Gondwanan platform during a series of marked eustatic s
ea-level rises during the Mid-Late Ordovician and Early Silurian. In O
man no evidence has yet been found for the significant Late Ordovician
glacial event recorded from North Africa and Saudi Arabia.