Misfar Gr

Devonian sediments were first interpreted by Pokorny and Hopping (1964). The Misfar itself was first distinguished in well Misfar-1 (type section), which was drilled in 1973. First mentioned by Winkler (1975), as Misfar Formation. Elevated to Group status by Hughes Clarke (1988). "Due to its separated stratigraphic position, this Devonian sequence is deemed sufficiently important to warrant Group status, but no further subdivision is supported until a more consistent data set is available." Additional reference section is Hadh-1 in Central Oman. Column: Oman Subsurface

Synonym:

The Misfar Group is a sequence of (often organic) shales, quartzose sandstones (in the Misfar area only) and sandy limestones. " The two packages of Misfar Group sediments recognized to date" … Sequence stratigraphy: Both "belong to both the AP3 and AP4 Megasequences of Sharland et al. (2001, 2004). … Sharland et al. (2001) place their Emsian, MFS D20 and Pragian MFS D10 in marine mudstones towards the top and base, respectively, of the Misfar section (sensu Verstralen and Partington, 2000). Osterloff (2000b) questions the marine character and correlatability of the lower mudstone. The younger Famennian – Tournaisian section could encompass the latest Famennian MFS D30 of Sharland et al. (2001).

No obvious log characteristics allow these ‘sequences’ to be more widely recognized or correlated. Reworking of the earlier Middle – Late Devonian sediments into successively younger sequences also hampers an accurate age assessment. With these restrictions it is difficult to establish systematic facies successions or correlate the available preserved sections."

"

The limestones contain ostracods and stromatolite-like structures, whilst the fine clastics yield palynomorphs. The Emsian – Eiffelian palynomorph assemblages are assigned to Palynozone 2121 (Grandispora velata). The Famennian – Tournaisian assemblages reviewed by Osterloff (2000b) have not been assigned to a palynozone. Miospores recorded in these younger Misfar sections include Aratrisporites saharaensis, Vallatisporites pusillites, V. vallatus and Retispora lepidophyta. The latter species is essentially restricted to the Famennian, but is commonly reworked into the Carboniferous.

A stratigraphical footnote to the ‘Misfar story’ is provided by Penney (1998), who recorded distinctly younger miospore assemblages of a general Tournaisian? – Visean age in one well from the Ghaba Basin. Unconformably overlain by Upper Gharif Gr, this early Carboniferous ‘remnant’ is a succession of sands and clays, with dolomite and limestone streaks and has not been formally assigned to any lithostratigraphic unit. A 10-m thick dolomite in the upper part of the section could potentially contain the late Visean MFS C10 surface of Sharland et al. (2001)."

"The geological history of the large time gap between deposition of the Haima Supergroup Gr and the Haushi Gr in which the Misfar Group sediments occur is largely unresolved. Little is known about sedimentation in the Oman realm during the Devonian – early Carboniferous as hardly any sedimentary record is preserved. The distribution of the Misfar sediments is patchy along the eastern and northeastern flanks of the South Oman Salt Basin, with rare occurrences in the Ghaba Basin of North Oman. The thickness, distribution and preservation of Misfar Gr sediments were probably controlled at least in part by Ara salt withdrawal and dissolution. Konert et al. (2001) discuss the distribution of the Silurian – Devonian sediments on the Arabian Plate. Lower Devonian sediments are missing in Iraq and Turkey whereas a complete Devonian section is present in Saudi Arabia. Devonian sediments were therefore also probably more widespread in Oman and subsequently eroded during the Carboniferous, as also suggested by Faqira et al. (2009). Near the present-day east coast of Oman, erosion cuts down to Huqf Supergroup GR sediments and even basement. In the north (Al Jabal Al Akhdar, Saih Hatat) gently folded Neoproterozoic – Cambrian sediments are unconformably overlain by Permian carbonates. . . .

Osterloff (2000b) reports coastal plain and shoreface sandstones that are capped by a marginal-marine unit that may represent a flooding event in deposits tentatively assigned to an Emsian – Eifelian sequence. Marine, ostracod-rich carbonates are also recorded in the upper part of the section from the Misfar Gr area. A younger Famennian – Tournaisian sequence is dominated by fluvial and flood-plain deposits, grading up to possible marginal marine facies."