Evolution of the Arabian continental margin of the northern Dibba Zone, eastern United Arab Emirates and Oman

Accepted Manuscript Evolution of the Arabian continental margin of the northern Dibba Zone, eastern United Arab Emirates and Oman David J.W. Cooper, Christopher Toland, Mohammed Y. Ali, Owen Green PII: DOI: Reference:

S1367-9120(16)30274-7 http://dx.doi.org/10.1016/j.jseaes.2016.08.021 JAES 2798

To appear in:

Journal of Asian Earth Sciences

Received Date: Revised Date: Accepted Date:

5 April 2016 23 August 2016 26 August 2016

Please cite this article as: Cooper, D.J.W., Toland, C., Ali, M.Y., Green, O., Evolution of the Arabian continental margin of the northern Dibba Zone, eastern United Arab Emirates and Oman, Journal of Asian Earth Sciences (2016), doi: http://dx.doi.org/10.1016/j.jseaes.2016.08.021

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Evolution of the Arabian continental margin of the northern Dibba Zone, eastern United Arab Emirates and Oman

David J.W. Cooper1*, Christopher Toland2, Mohammed Y. Ali3 and Owen Green4

1

DJW Cooper (Geological Consultancy) Limited, 6 Calverley Park, Tunbridge

Wells, Kent, TH1 2SH United Kingdom. [email protected] (corresponding author) 2

Oolithica Geoscience Limited, Lower Ground Floor, 53/57 Rodney Rd.,

Cheltenham, Gloucestershire GL50 1HX United Kingdom. [email protected] 3

The Petroleum Institute, P.O. Box: 2533, Abu Dhabi, United Arab Emirates.

[email protected] 4

Department of Earth Sciences, Oxford University, South Parks Road, Oxford

OX1 3AN United Kingdom. [email protected]

Abstract The southern margin of the Musandam Mountains (UAE and northern Oman) preserves a Late Permian to Late Cretaceous Neo-Tethyan platform margin sequence that provides important insights into the switch from deposition in shallow shelf to deeper-water margin slope environments. New biostratigraphic dating resolves ambiguities in previous works and better constrains the timing of the stages 1

in the development of the south Musandam platform margin and their link to the wider Oman tectonic framework. The accumulation of Late Permian to Late Triassic mainly dolomitised shelf carbonates along this sector of the nascent Neo-Tethyan margin was ended by a phase of margin-edge collapse linked to the onset of a major phase of Neo-Tethyan rifting and extension, and deposition of a fore-reef talus assemblage. This is newly dated as also being Late Triassic (Norian-Rhaetian) and termed the Kharas Formation. Following non-deposition, or possible erosion of Early Jurassic deposits, differential subsidence in the Middle Jurassic led to deposition of on-lapping deeper-shelf/ slope facies peri-platform lime mudstones, fine grained turbidites and minor, channelised coarser-grained graded conglomerates and packstones (Sumeini Group) along the southern side of the Musandam platform. In the west, oolitic peloidal packstone and grainstone shoals were deposited, here termed the Jarief Formation. Their Bathonian-Callovian age is coeval with the regional development of oolitic facies on the carbonate platform, linked to a midJurassic sea-level highstand, and their redeposition into the adjacent Hawasina Basin as turbidites of the Guwayza Formation of the Hamrat Duru Group. Uplift and destabilisation of the margin of the carbonate platform throughout Oman in the Late Jurassic during a mild compressional regime cut off the coarser sediment supply to the Jarief Formation, which was superseded by deposition of Sumeini Group slopefacies lime mudstones with numerous intraformational truncation surfaces. Slope facies sedimentation then persisted along the length of the southern edge of the Musandam platform as the margin relaxed and subsided until the end of the Early Cretaceous. Uplift of the margin edge, related to changing regional compressive stresses as seafloor spreading increased in the South Atlantic and intra-oceanic subduction in Neo-Tethys initiated creation of the Semail Ophiolite, led first to

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collapse along the shelf edge, generating the thick and highly channelised post Aptian Ausaq Formation mega-breccias. This marked the end of the passive margin as a thick, Late Cretaceous predominantly shale and chert succession was deposited as the margin subsided with continent-ward migration of the foredeep that developed ahead of final emplacement of the Neo-Tethyan Hawasina Nappes and Semail Ophiolite during the Santonian.

Key Words Oman margin; Neo-Tethys, Musandam; fore-reef talus; carbonate slope sedimentation; Kharas Formation.

1. Introduction During the Late Permian and Mesozoic, the area now occupied by the Oman Mountains lay on the edge of the Arabian Plate adjacent to the Neo-Tethyan Ocean and formed part of the great Neo-Tethyan passive carbonate margin. The shelf-edge to the margin is rarely exposed in Oman, on account of its burial beneath a thick cover of allochthonous Neo-Tethyan oceanic sediments (Hawasina Complex), deepocean and subduction-related sediments, volcanics and mélanges (Haybi Complex) and the Cenomanian Semail Ophiolite. These were emplaced onto the continental margin during the Late Cretaceous and now form the Oman Mountains, which extend from the Musandam Peninsula over 500 km to the SE (Glennie et al., 1973, 1974; Searle and Malpas, 1980, 1982; Coleman, 1981; Lippard et al., 1986, Robertson and Searle, 1990; Rabu et al., 1993; Warren et al., 2005; Rioux et al., 2012, 2013).

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The Musandam Peninsula of northern Oman and United Arab Emirates (Figure 1) comprises a mainly limestone and dolomite sequence some 4km thick – the Hajar Supergroup - that was deposited along this Neo-Tethyan passive carbonate margin (Hudson et al., 1954a; Hudson and Chatton, 1959; Hudson, 1960; Allemann and Peters, 1972; Glennie et al., 1973, 1974; Ricateau and Richie 1980; Styles et al., 2006; Maurer et al., 2007, 2009; Fontana et al. 2010; Clarkson et al., 2013). Its present-day outcrop as an uplifted mountainous area reaching over 2,000 m above sea-level owes its development primarily as a pre-Late Miocene west-facing, locally imbricated, thrust-cored culmination resulting from the collision between the Arabian and Eurasian plates at the southern end of the Zagros belt (Searle 1988a, b; Searle et al., 2014). The southern edge of this ‘Musandam platform’ sequence represents an obliquerifted SW-NE trending passive margin (Robertson et al., 1990), arranged at a high angle to the inferred N-S orientation of the shelf edge to the south (Boote et al., 1990), and marked by an abrupt, mainly faulted transition to coeval deeper-water sediments and subordinate volcanics of the Dibba Zone (Figure 2a, b). The Dibba Zone marks the northern end of preservation of the major thrust sheets of NeoTethyan deeper-water units and the Cenomanian Semail Ophiolite (Figure 2c; Glennie et al., 1974; Searle et al., 1983; Searle, 1988a, b; Robertson et al., 1990; Le Métour et al., 1992a; Styles et al., 2006). The southern edge of the Musandam Peninsula provides a critical location to investigate the transition from platform to slope facies. Facies changes in the Musandam platform sequence point towards a general change from interior platform to more open shelf and shelf-edge conditions toward this southern boundary with the Dibba Zone (Searle et at., 1983; Robertson et al., 1990; Styles et al., 2006). The

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sedimentary sequences of the southernmost part of the Musandam Peninsula also preserve the transition to deposition in a slope environment with the preservation of fore-reef debris aprons, deep-shelf and slope facies, and evidence for multiple stages of failure of the carbonate margin, recorded in thick limestone conglomerates. The ages of these transitional shelf-edge to slope units have previously been uncertain. They were assigned by Le Métour et al. (1992a) in their mapping the Oman sector of the Dibba Zone and Musandam Mountains partly to the Late Triassic-Jurassic (Kharas Formation). Searle et al. (1983) and Robertson et al. (1990), working in the western Dibba Zone, make passing reference to these units and assigned at least parts of them to the Late Triassic-Early Jurassic. Searle et al. (1983) correlated the units with the Jabal Wasa Formation that crops out as part of the mainly slope facies Permian-Cretaceous Sumeini Group at Jabal Sumeini 90 km to the south, with the exception of small isolated outcrops at Jabal Agah, which they treated as part of the Jurassic/ Cretaceous succession. Conversely, Styles et al. (2006) in their mapping of the UAE part of the Dibba Zone assigned these units wholly to the Late Cretaceous Ausaq Formation. This paper describes these shelf-edge and slope units and presents new age data that allow a clearer understanding of the evolution of this part of the Neo-Tethyan shelf through its development to destruction in the Late Cretaceous during the emplacement of the Semail Ophiolite and related thrust sheets of deeper-water NeoTethyan sediments onto the Arabian Plate margin. We identify a Late Triassic forereef/ slope-apron facies tract which we call the Kharas Formation, and a Middle Jurassic shoal complex which we call the Jarief Formation. These pass stratigraphically upwards into the outer shelf and slope facies of the Sumeini Group

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and thence to the early Late Cretaceous Ausaq Formation and overlying foredeep shales and cherts of the Muti Formation.

2. Structural overview of the Musandam Peninsula and northern Dibba Zone The Neo-Tethyan carbonate platform succession formed during initial Neo-Tethyan rifting in the Mid to Late Permian. Passive margin sedimentation patterns persisted until the start of the Late Cretaceous, when this part of the Neo-Tethyan margin was disrupted by the processes that culminated in the obduction of the Semail Ophiolite. Emplacement of the Semail Ophiolite and the sub-ophiolite Hawasina and Haybi Complex thrust sheets in the northern Oman Mountains was broadly from the east (Searle et al., 1983). Final emplacement onto the foundered Oman margin occurred during the Late Santonian (Warburton et al., 1990). Thrust stacking in the NeoTethyan units is generally in sequence. Thus, margin-proximal units (Hamrat Duru Group – broadly representing continental rise environments, Glennie et al., 1974; Béchennec et al., 1990; Cooper, 1990; Blechschmidt et al., 2004) are located structurally towards the base of the allochthon, whereas margin-distal units such as the Shamal Formational basin cherts and the Jabal Qamar rifted horst limestones are found towards the top of the stack (Figure 2c). These are in turn structurally overlain by syn-subduction sedimentary and tectonic mélanges and metamorphic rocks that are themselves structurally overlain by the Semail Ophiolite. This general pattern is disrupted by local out-of-sequence thrusting and complex NW-directed transport along the northern side of the Dibba Zone, at least in part linked to oblique ramping and buttressing between the SE facing south Musandam margin re-entrant

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during the later stages of ophiolite emplacement (Figure 3, Glennie et al., 1974; Searle et al., 1983; Searle, 1988a; Robertson, 1987; Robertson et al., 1990). Passive margin conditions resumed during the Late Campanian and Maastrichtian (Nolan et al., 1990; Skelton et al., 1990). They persisted until the Late Oligocene, when a second phase of compression formed the huge Musandam culmination as the Arabian plate started to collide with the Eurasian plate (Searle et al., 1983; Searle, 1988b; Searle et al., 2014). The whole of the Musandam Peninsula has been uplifted and tilted such that the lowest stratigraphic levels are now mostly exposed in the SE (Figure 1) and higher levels are prevalent in the west and north of the peninsula. Culmination was driven by deep-level thrusting involving both basement and Neo-Tethyan units (Searle et al., 1983; Searle, 1988b; Searle et al., 2014). The west-facing frontal fold to the Musandam culmination forming in the hanging wall of the Hagab thrust. This mountain-scale anticline plunges to the south and the Musandam shelf succession is buried beneath recent and sub-recent wadi deposits at the western end of Batha Mahani. The southwestern Musandam platform sediments are also folded along a hinge line that is broadly parallel to the SW-NE axis of the Dibba Zone, dipping to the SE at between 30° in the west (Batha Mahani area) and 70+° in the east. Uplift of the Musandam Peninsula and related culmination collapse also resulted in complex down-to-the-SE normal faulting along the boundary with the Dibba Zone, with a throw of up to 4 km at the eastern end of the Dibba Zone (Searle et al., 1983, 2014; Searle, 1988b; Tarapoanca et al., 2010). This compressive phase ended before the mid Miocene, as demonstrated by the truncation of thrusts by a mid-Miocene unconformity (Searle et al., 2014).

3. Location and contest of the Kharas and Jarief Formations

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There are two broad outcrop areas of the Kharas Formation. The first and most extensive is as part of the Hajar Supergroup carbonate platform succession along the southern edge of the Musandam Peninsula. Here it is exposed in a strip up to 2.5 km wide, bordered to the SE by the allochthonous Hawasina, Haybi and ophiolite units of Dibba Zone. In this sector, the Musandam platform succession is folded along the SW-NE axis sub-parallel to the Dibba Zone, dips to the SE and is overlain unconformably by the Kharas Formation from Wadi Ausaq eastwards (Figures 3 and 4). The Kharas Formation lies unconformably on the mainly dolomitised carbonate platform units of the Rus Al Jibal Group (Late Permian-Middle Triassic, Maurer et al., 2007, 2009; Clarkson et al., 2013) between Zighy Bay in the NE to the Ausaq bowl of the north-central part of the Dibba Zone. Immediately to the west, on the western side of the Ausaq bowl and along the Wadi Ausaq, it lies on the Late Triassic Milaha Formation. The width of the exposure reflects bedding dipping to the SE at an inclination not much greater than the dip of the land surface. Exposures along the sides of deeply incised wadis show evidence for both reverse and normal faults that strike broadly parallel to the Dibba Zone boundary. The second outcrop area of the Kharas Formation is along the axis of the Jabal Agah anticline in the western part of the Dibba Zone, 3 km from the southern edge of the Musandam Peninsula (Figures 3 and 5). Jabal Agah is a NNE-SSW trending WNW-facing doubly-plunging anticline, locally thrust along its WNW edge. It comprises mainly Sumeini Group fine-grained deeper-shelf and slope facies sediments. Normal faulting along the crest of the anticline brings the Kharas Formation to the surface, as the stratigraphically lowest unit.

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The Jarief Formation, which is restricted to Jabal Agah, lies stratigraphically between the Kharas Formation and the Sumeini Group, under which it lies with a conformable contact. The Sumeini Group is overlain with a generally erosive contact by Ausaq Formation limestone breccias and conglomerates, although these are only patchily preserved. The Ausaq Formation is overlain by shales, cherts and lesser limestone turbidites and debris flows of the Muti Formation, deposited in the foredeep that developed as a response to subduction and the initial phase of tectonic emplacement of the Hawasina thrust sheets and Semail Ophiolite (Robertson, 1987; Robertson et al., 1990). The contact between the Muti Formation and the Sumeini/ Ausaq is broadly conformable, but modified by small-scale faulting consequent to the significant contrast in competence between the units.

4. Kharas Formation of the southern Musandam Peninsula: stratigraphy and sedimentology The southern side of the Musandam Mountains bordering the Dibba Zone is marked by a unit over 200 m thick of hard crystalline and recrystallized limestone conglomerates, granule wackestones and packstones, and peloidal and oolitic packstones and grainstones. Coarser grained beds frequently contain abundant coral debris. This is the Kharas Formation. The Kharas Formation typically forms brownish weathering, steep, rugged and rubbly hillsides cut by precipitous gorges. Access is difficult and, although the unit is well-exposed in the gorges, internal bedding and structures are poorly defined (Figure 6a-c). This is, in part, a consequence of the strong recrystallization, with the

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destruction of grain-size and compositional differences that would otherwise influence weathering patterns and the surface expression of internal sedimentary structures. Instead, the limestone weathers as a mostly homogenous mass, with sharp ridges and pits that are encrusted by brown insoluble residues (Figure 7a). When combined with an absence of marker horizons and faulting (both normal and reverse) on a scale of tens of metres, it is not possible to determine conclusively fine stratigraphic detail. The Kharas Formation rocks are also pervasively jointed; weathering along these joints breaks the strata into large, frequently chaotic boulders. 4.1. Description of the Kharas Formation The Kharas Formation comprises a comparatively limited range of carbonate lithologies, although poor definition in outcrop makes it difficult to establish their relative proportions and the lateral extent of individual lithofacies. The most abundant facies comprise irregular cobble, pebble and granule limestone conglomerates and breccias, in which rounded to sub-angular clasts generally rarely exceed 15 cms (Figure 7b-d), although they occasionally reach almost 1 m in diameter. Clasts in these rudstones, and more rarely floatstones comprise lime mudstones, wackestones with lesser fine to coarse-grained biogenic and detrital carbonate allochems, broken shell and coral debris, and tabular broken lime mud flakes. Some clasts show evidence of soft-sediment deformation, including squeezing and bending around other clasts. The matrix is typically a poorly-sorted wackestone, but may locally comprise irregular patches of well-sorted fine to medium-grained cortoid peloidal grainstones with a sparry calcite cement and

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interstitial spaces almost devoid of mud. Terrigenous sand is also occasionally found in the matrix. Bedding is typically massive and indeterminate, but poorly graded, metre-scale beds with irregular erosive bases are present, in particular in the lower half of the formation. Such beds typically fine upwards from pebble/ small cobble grade to very coarse/ granule grade, with irregular coarser grained bands frequently developed. Bedding surfaces, inferred from the presence of abrupt differences in grain size, are amalgamated, with no difference in cementation or recrystallisation across boundaries. As a result, these bedding surfaces are not picked out by present-day erosion or weathering. The second main facies present comprises well-sorted grainstones and packstones with a sparry calcite cement. These are thick-bedded (metre-plus), again with very poorly-defined bed boundaries. They are highly recrystallized and freshly broken surfaces have a diffuse milky green-grey appearance. Sedimentary structures are limited to fragmentary areas of parallel laminations and possible dune bedding. Allochems mainly comprise well-rounded and well-sorted, medium to coarse-grained peloids. These are characteristically defined by thin micrite envelopes around a sparry/ microspar interior. The micrite envelopes are usually structureless, but poorly-defined concentric laminae are sometimes present. Both the interior and exterior edges of these envelopes are typically rimmed by microspar giving a fuzzy appearance. Dissolution of the interior of grains beneath their micrite envelopes appears to have taken place at an early diagenetic stage, with rare examples of partial geopetal infills, the remaining space being filled by sparry calcite. Other allochems comprise a wide range of skeletal remains, including abundant broken molluscan and gastropod debris, sparry echinoderm plates, algal and coralgal

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fragments, and agglutinate, miliolid and rotalid foraminiferal tests. These also tend to be poorly preserved, with micrite envelopes and internal spaces are spar-filled. The interstitial spaces between allochems are similarly filled with sparry calcite with crystal sizes increasing from the grain boundaries into the centre of the voids. Outcrops of the Kharas Formation between the Ausaq bowl in the east, and Wadi Laqras and the UAE-Oman border, suggest the formation is about 200 m thick. They mainly comprise coarse bioclastic granule rudstones with abundant broken coral debris and irregular void-filling wackestones and cortoid, skeletal and peloidal grainstones and packstones. There are also abundant pebble and cobble rudstones throughout the section. The lower half of the formation tends to be more clearly bedded while the upper half is massive. In this area, peloidal, cortoid and more rarely oncolytic and oolitic packstones and grainstones beds locally pass laterally into irregularly-edged areas of coarse skeletal-coralline limestone rudstone with a muddy wackestone or packstone matrix. The sections further west at Wadi Bidi in Oman reach about 350 m thick and comprise a lower unit of mainly coarse packstones and grainstones, a middle unit approximately 100 m thick dominated by cobble rudstones and an upper unit about 200 m thick which comprises mainly granule and very coarse-grained packstones and wackestones. The Kharas Formation thins structurally to the NE of Wadi Bidi as a consequence of normal faulting which cuts out the upper parts of the unit. The Kharas Formation of Jabal Agah is broadly similar to that seen elsewhere (Figure 6e, f), but with a higher proportion of reef-derived debris. It is mostly pervasively recrystallized, with a milky light grey-green colour and the concomitant loss of definition of finer-scale internal structures. It locally contains abundant

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skeletal-coralline limestone boundstones with broken coral fragments that reach 50 cms across (Figure 7e). Large irregular voids between coral heads have concentric bands of fringing calcite up to 1 cm wide with residual void areas filled with pale lime mud (Figure 7f). Elsewhere, voids appear to be filled with peloidal and occasionally oolitic grainstones and packstones. Other beds appear more chaotic, with decimetre to centimetre-scale coral debris, peloidal packstone and wackestones clasts, lime mudstone clasts and broken shell debris in a matrix of paler wackestones containing variable proportions of fine sand to granule grade limestone allochems. Again, irregular voids are filled by fringing calcite and lime mud (Figure 7f). These beds locally pass laterally into peloidal and oolitic and cortoidal grainstones and packstones. The boundaries are usually sharp but irregular. While outcrops areas are insufficiently extensive to determine precise relationships, these grainstones and packstones appear to be channelised as well as infiltrating pre-existing voids in coarser-grained deposits. 4.2. The lower boundary of the Kharas Formation The Kharas Formation lies unconformably above the shelf carbonates of the Hajar Supergroup (Figure 8a, b). It rests mainly on the Permian-Middle Triassic Rus Al Jibal Group, with the exception of the southwestern exposures along Wadi Ausaq where it lies on the Late Triassic Milaha Formation. The contact above the northern and western sides of the Ausaq bowl (where access is possible) is stratigraphic and marked by a cobble to small boulder conglomeratic unit that varies from 1 m to over 10 m thickness that rests unconformably on the Rus Al Jibal Group and Milaha Formation limestones respectively. The clasts comprise a range of limestones and dolomites derived from the underlying Rus Al Jibal and

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Elphinstone groups, in particular sub-rounded clasts of fine-grained dolomite and limestone, including boulders containing Megalodontid bivalves, also seen in outcrop in the Milaha Formation. They are well-cemented but do not show the intense recrystallisation that characterises much of the Kharas Formation. The contact is irregular, with evidence of gullying of the basal surface, although there is insufficient exposure to reconstruct the degree of topography along the erosive unconformity. The thickest of the basal conglomerates are found on the hillside on the western side of the Ausaq bowl. Here similar conglomerates form lenticular horizons in the adjacent Milaha Formation. Elsewhere, where the contact could be accessed, the lowest beds of the Kharas Formation do not contain these comparatively unrecrystallised conglomerates and there is an abrupt change from the Rus Al Jibal and Elphinstone groups to more typical Kharas lithologies. 4.3. The upper boundary of the Kharas Formation The uppermost Kharas Formation locally shows an increased amount of graded conglomeratic limestones. In Wadi Laqras, a sequence 10 m thick starts with a cobble and boulder rudstone that, in addition to the range of skeletal and coral boundstones, cortoid peloidal packstones and wackestones that typify the coarsergrained Kharas Formation, includes blocks and rafts of finer-grained well-bedded limestone akin to the overlying Sumeini Group. The Kharas Formation is overlain by beds 10 to 30 cms thick of micro-laminated graded lime-siltstones and mudstones of the Sumeini Group. The contact, discussed in more detail in the section below on the Sumeini Group, is seen in the central and eastern Khabb bowl, along Wadi Laqras, and the upper reaches of Wadi Khabb and

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NE of Satkha village (Figure 8c). It is irregular and abrupt (Figure 8d), with the Sumeini Group draping and onlapping the underlying Kharas Formation. The contact is however frequently modified by low-displacement faulting that exploits joints. The Sumeini Group is folded over brittle offsets in the Kharas Formation and fault gouge breccias are developed along the contact. The Kharas Formation is overlain with a deeply erosional unconformity by conglomerates of the Ausaq Formation from the western end of the Khabb Bowl to Wadi Ausaq, and also in the Wadi Bidi area in Oman (Figure 3), and the Sumeini Group is missing. 4.4. Age of the Kharas Formation The Kharas Formation comprises mainly redeposited limestones, with the attendant problems in determining to what extent included faunal remains were synchronous with deposition or derived from the erosion of older stratigraphic horizons. In many specimens, pervasive recrystallisation obscures fine detail necessary for positively identifying biogenic debris. However, a range of packstone and grainstone samples have yielded identifiable fauna, all of which point towards a Late Triassic, NorianRhaetian age for the unit (Table 1). In the Wadi Ausaq area, the uppermost few metres of the Kharas Formation have yielded occasional in-situ ammonoids, including the ammonite Pinacoceras matternichi (Norian) and the uppermost NorianRhaetian orthocone nautiloid Rhabdoceras sp. The youngest rocks beneath the Kharas Formation are those of the Milaha Formation, into which the Kharas also passes laterally in the Ausaq Bowl area. Maurer et al. (2007), working in the Wadi Bih area on the western side of the Musandam Peninsula, suggest the Milaha Formation is Late Norian (Sevatian) in

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age. They date the overlying Ghalilah Formation as spanning the Sevatian and Rhaetian, into the Early Jurassic. This lies directly on the Milaha Formation across the Musandam platform with the exception of the southern edge where the Kharas Formation lies above Milaha sediments. Le Métour et al. (1992a), in defining the Kharas Formation, also suggested a predominantly Late Triassic age. This was based its relationship with the underlying Rus Al Jibal Group, on their observation of the apparent inter-fingering of the unit with the Milaha Formation in the upper reaches of Wadi Kharas (Wadi Laqras) and on poorly preserved fauna within the Kharas Formation. However, they inferred deposition of the formation extended into the Early Jurassic, from fauna in a single block from a limestone conglomerate bed from the Oman sector which yielded a ‘Middle Liassic’ benthic foraminiferal assemblage (Haurania amiji, Pseudocyclammina liasica, Glomospira sp. and Glomospirella sp.). It is thus possible that deposition of the Kharas Formation continued into the Early Jurassic, but that upper levels were subsequently mostly eroded back to the Late Triassic. Styles et al. (2006) referred to these rocks in the UAE as the ‘Sowdah’ unit of their Late Cretaceous ‘Ausaq Conglomerate Formation’. However, with the age of these rocks now confirmed as Late Triassic and possible Early Jurassic, it is proposed that the term ‘Kharas Formation’ should be used for occurrences of these rocks in both Oman and the United Arab Emirates, following the terminology developed by Le Métour et al. (1992a) for this unit the Oman sector. 4.5. Depositional Environment of the Kharas Formation The sedimentology of the Kharas Formation suggests deposition in an unstable environment adjacent to reefal build-ups (the bioherms of Searle et al., 1983).

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Cobble and rare boulder conglomerates appear to be made up mainly of reef-derived and finer-grained shallow-water platform lithologies, some fully lithified, others less so and showing evidence of soft-sediment deformation. A lack of sorting, or poorlydeveloped grading and clast or wackestone-matrix supported conglomerates and breccias suggests deposition from submarine debris flows and hyperconcentrated density grainflows cf Mulder and Alexander (2001). Broken coral rudstones, comprising a mass of coarser and finer grained coral fragments and recycled limestone with an open framework into which lime mudstone and finer sand and granule sized particles filtered, suggest deposition in a tumbled talus pile adjacent to reefal build-ups. The absence of well-defined bedding planes suggest deposition was essentially continuous, with early sparry cementation preserving original voids, suggesting a predominantly intraformational origin arising from instability along the margin edge during the period of deposition of the Kharas Formation. Poorly-sorted finer-grained wackestones and packstones containing small coral heads and other shell debris suggest lower-energy debris-flow, or bioturbated deposits. Higher energy lime-sand shoals also developed in shallower waters, which formed the source of channelised grainstones and packstones. While pervasive recrystallisation masks most sedimentary structures, relict parallel laminations and ripples suggest they probably represent deposition from concentrated density flows and proximal turbidites cf Mulder and Alexander (2001). The Kharas Formation was deposited along the southern edge of the Musandam platform, following erosion of the shelf edge into the Milaha Formation and Rus Al Jibal Group that now form its substrate. For most of the preserved length of exposure, the Kharas Formation was deposited on an underlying rock surface. Only in the Ausaq Bowl area are erosion products preserved, as the limestone

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conglomerate beds at the base of the Kharas Formation. There is little evidence to suggest that the down-cutting into older units at the base of the Kharas Formation was the product of large-scale catastrophic collapse of the shelf edge, as opposed to erosion. It is notable there are no thick coeval Late Triassic shelf-derived conglomerates in the Hamrat Duru Group, in particular the Dibba unit, which generally shows the depositional signature of a margin-proximal base-of-slope/ continental rise environment (Figure 2; Cooper, 1986, 1990) and which might be expected to preserve evidence of such an event.

5. Jarief Formation The Jarief Formation is limited in outcrop to the Jabal Agah culmination. It forms blocky-weathering areas of thick-bedded grainstones and packstones along the western part of the anticline crest (Figure 5). Styles et al. (2006) considered this unit, together with the Kharas Formation (as defined here) of Jabal Agah as an informal ‘Jarief Reef’ unit within the Late Cretaceous succession. Detailed mapping and biostratigraphic investigation indicates these grainstone and packstone form a distinct unit between the Kharas Formation and Sumeini Group, and we propose rocks be assigned to a newly defined ‘Jarief Formation’. The Jarief Formation comprises upwards of 30 m of mid-grey weathering recrystallized medium to coarse-grained packstones and grainstones. Individual beds are typically 1-2 m thick and amalgamated (Figure 10a, b). They are mostly poorly graded and devoid of sedimentary structures, although diffuse parallel laminations and metre-scale dune-bedding are occasionally seen in beds that have suffered less recrystallization (Figure 10c). The bases of some beds, in particular in the lower

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stratigraphic exposures contain pebble conglomerates (Figure 10d), clasts being packstones and very fine-grained recrystallized lime mudstones with a coarse to granule grade packstone matrix. These are laterally impersistent and channelised. In the upper part of the formation, the tops of beds are graded. The upper few centimetres comprise mainly micrite, and thin argillaceous interbeds are also sometimes preserved. The allochems in the grainstones and packstones comprise well-rounded cortoidal peloids with locally abundant ooids, algal, gastropod and mollusc fragments, benthic foraminifera (agglutinates and miliolids) and echinoderm plates. Grains are mostly well-rounded. Many grains have been reduced to diffuse micrite envelopes with recrystallized interiors. Micrite envelopes are fringed with microspar, with larger interlocking sparry calcite crystals filling the interior of the grain. More rarely, concentric bands of fine-grained calcite crystals within grains suggests a relict ooid structure. Sparry calcite cements frequently preserve a very open framework, indicating cementation was complete before significant compaction occurred. 5.1. Boundaries of the Jarief Formation The stratigraphic context of the Jarief Formation of Jabal Agah is illustrated in Figure 11. The base of the Jarief Formation is not seen on account of faulting. There are similar facies in parts of the Kharas Formation, but a direct link is not observed. The Jarief Formation is overlain stratigraphically by the Sumeini Group (Figure 10b, Figure 11 inset e). Peliodal grainstones and packstones pass abruptly upwards into light grey very fine-grained micro-laminated and rippled lime siltstones and mudstones. The contact is clearly conformable in those areas where not disrupted by

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small-scale faulting and layer parallel shearing resulting from differential movement and competence contrasts during folding and thrusting of the Jabal Agah culmination. 5.2. Age of the Jarief Formation Three specimens from the Jarief Formation have yielded Middle Jurassic (BathonianCallovian) biostratigraphic data (Table 2). 5.3. Depositional environment of the Jarief Formation The highly recrystallized nature of the Jarief Formation, together with a paucity of sedimentary structures renders environmental analysis somewhat speculative. In the main, the thick bedded grainstones and packstones contain little interstitial lime mud indicating mass deposition in a high energy environment or one in which fine-grained components have been winnowed out. This and the albeit rarely preserved dune bedding suggest deposition in a shallow, possible shoal-water environment, but rapid redeposition in a deeper shelf setting from a shallower-water part of the shelf cannot be excluded. 6. Sumeini Group The Sumeini Group of the Dibba Zone has been discussed by Robertson et al. (1990), Watts (1990), Le Métour et al. (1992a) and Styles et al. (2006). It comprises a series of para-autochthonous and locally autochthonous units adjacent to the southern side of the Musandam shelf carbonates that stretch from the Ausaq gorge in the west to Bidi in the east (Figure 3). A second group of outcrops occur in the western part of the Dibba Zone where they form Jabal Agah and Jabal Al Gharaf and a number of near-by smaller areas (Figure 3). While Jabal Agah is a thrust-cored anticline around which Muti Formation cover sediments are also folded, the smaller outcrops of Sumeini Group rocks in the Dibba Zone have been interpreted as 20

possible olistostromes or rafts that slumped into the Late Cretaceous Muti Formation (Aruma) foredeep (Robertson et al., 1990). Most of the Sumeini Group comprises calcilutites bedded on a 10-30 cms scale with argillaceous partings. Beds are typically finely laminated on a millimetre scale (Figure 12a). Laminae of slightly coarser-grained limestone are starved and pinch out over 10s of centimetres. Coarser-grained (silt to fine sand grade) bases to beds may be rippled; starved ripples are common. Load structures penetrating underlying laminae suggest rapid deposition onto a soft substrate. Climbing ripples (Figure 12b) are also seen. Individual beds are separated by thin (to 1 cm) shale or marly partings. Bioturbation is usually absent or limited to the uppermost parts of beds. A dark grey to black colour on fresh surfaces and rare petroliferous odour suggests deposition in anoxic conditions. The Sumeini Group in Wadi Laqras and the upper reaches of Wadi Khabb shows more pervasive bioturbation (Figure 12c) suggesting more oxygenated conditions. A stratigraphic contact with the Kharas Formation in the Ausaq Bowl area shows an abrupt transition to these fine-grained lime mudstones which drape and can be seen to onlap the Kharas at a low angle. Locally, well-developed 100 m wide channels are seen close to the base of the Sumeini Group (Figure 12d). They are mostly filled with laminated calcilutites, with lesser lenticular limestone conglomerates and graded grainstones. Channels are otherwise rarely seen in the Sumeini Formation. Instead, large slumps scars and intraformational truncation surfaces are common (Figure 11 inset c), indicating a steep slope by-passed by coarse-grained sediment input. The upper part of the stratigraphy is characterised by a unit approximately 40 m thick of

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characteristic pink-grey fissile argillaceous calcilutites and calcisiltites with shale partings that are overlain by up to 15 m of more massive finely laminated lime mudstones interbedded with fine-medium-grained peloidal and oolitic calci-turbidites. This unit is not always present, possibly a product of tectonic removal through faulting, or erosive removal during the deposition of the overlying Ausaq Formation conglomerates. The precise thickness of the Sumeini Group in most places cannot be determined accurately due to internal folding and faulting and an absence of marker horizons. However, the succession in the Jabal Yaweed (Ausaq-Khabb) area is at least 300 m thick. The succession in Jagal Agah is about 200 m thick (Figure 11). 6.1. Age of the Sumeini Group The Sumeini Group limestones have yielded little dateable material. A single coarser-grained channelised peloidal grainstone at the north-western end of the Khabb bowl approximately 30 m above the contact with the Kharas Formation yielded fauna indicative of the Mid-Late Bathonian (Table 3). This is the essentially same age as the Jarief Formation grainstones and packstones on Jabal Agah. The Sumeini Group on Jabal Agah above the Jarief Formation (Figure 10) has yielded a Late Tithonian microfossil assemblage, (Table 3, see also photomicrographs in Figure 9q-x). Allemann and Peters (1972) reported Early Cretaceous foraminifera (Albian to Cenomanian), suggesting deeper-shelf and slope conditions persisted between the Middle Jurassic to start of the Late Cretaceous.

7. Ausaq Formation

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The Ausaq Formation is a cobble to large boulder mega-breccia/ conglomerate with a deeply erosive base and corresponds to the Ausaq Conglomerate Formation of Styles et al. (2006). There are three main areas of outcrop. The first is along the SE side of the Musandam platform, from the NE end of Batha Mahani to the Khabb bowl. Smaller, isolated outcrops are found along the edge of the Musandam platform and Kharas succession to the east and west of Bidi village, in the Oman sector. The thickness of the Ausaq Formation is laterally variable and can reach in excess of 50 m. This reflects down-cutting into the underlying Sumeini Group, boulders and rafts of which are locally incorporated into the clast mix. This unit is equivalent to the lower sub-unit of the Sayja Member of the Muti Formation of Robertson (1987). It passes up abruptly into a sequence dominated by brown shales and siltstones with rarer thin siliceous finer-grained limestone beds, overlain by dark purple cherts and shales, the upper sub-unit of the Sayja Member of the Muti Formation of Robertson (1987). The second area is along the southern side of the folded Sumeini Group thrust sheet that extends from Jabal Yaweed and eastwards into Oman (Figure 12h). The Ausaq Formation is only intermittently preserved between the Sumeini Group and the brown and purple shales, cherts and thin silicified limestones of the Muti Formation. This contact also appears to have been reactivated as a normal fault, eliminating parts of the upper Sumeini Group and Ausaq Formation. The date of movement is unclear, but probably relates to a halo effect of Oligocene-Miocene culmination of the Musandam peninsula. The Ausaq Formation is also preserved intermittently immediately above the Sumeini Group around the edges of the Jabal Agah culmination (Figure 3). Again, the

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stratigraphically overlying Muti Formation is dominated by folded and thrust-bound imbricates of brown and purple shale, and purple cherts, but with a greater proportion of calcarenite turbidites, some with granule or pebble-grade bases, typically aggregated into packets up to 10 m thick. Detailed analysis of the Muti Formation of the Dibba Zone above the Ausaq Formation was outside the scope of the current investigation, but this unit has been considered particular by Robertson (1987). It is dated as Cenomanian to Campanian (Allemann and Peters, 1972; Glennie et al., 1974; Robertson, 1987; Robertson et al., 1990). The Ausaq Formation can be readily distinguished from conglomerates in the Kharas Formation. It is typically coarser, with a greater abundance of large cobbles and small boulders. It weathers in a more rubbly manner that picks out the range of different individual clasts in both colour and composition. This is different from the Kharas Formation, in which the high degree of recrystallization frequently makes it difficult to distinguish individual clasts, and in which the recrystallized clasts and matrix typically weather in an identical manner. The clast diversity is also greater in the Ausaq Conglomerate Formation. Clasts are derived mainly from the Hajar Supergroup, including Late Permian dolomites, Triassic limestones containing Megalodontid bivalves and chert (Figure 12g), with an Aptian grainstone reported by Searle et al. (1983). Reworked cobbles of recrystallized limestone breccias of the Kharas Formation are common in outcrops along Wadi Ausaq, where the Ausaq Formation cuts down through the Sumeini Group (Figure 12e) into the Kharas Formation, and boulders and rafts up to 10 m across derived from the Sumeini Group limestones are seen between Wadi Ausaq and the Khabb bowl (Figure 12f).

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The Ausaq Formation represents channelised debris flow deposits resulting from a phase of major collapse of the Musandam shelf edge, following which the input of carbonate into the Hawasina basin was greatly reduced. Sedimentation was then dominated by very fine-grained terrigenous clastics and radiolarian cherts suggesting a consequential rise in the level of the CCD (Cooper, 1990; Robertson et al., 1990).

8. Discussion 8.1. Pre-Kharas development of the Musandam area (Figure 13a) Following initial rifting in the Late Carboniferous-Early Permian, a major Middle-Late Permian rift event in the NE of the Gondwana supercontinent led to the initial separation of the Iranian-Afghan-Tibet micro-continental terrains from the Arabian plate and the development of the nascent Neo-Tethyan Ocean (Rabu et al., 1993, Pillevuit et al., 1997; Lee, 1990; Baud et al., 2001; Baud and Bernecker, 2010). In the Oman sector, this rifted margin was not straight, instead it appears to have been broken by a number of faulted (transform) off-sets (Figure 2b, Searle and Cooper, 1986; Cooper, 1990; Robertson et al., 1990; Pratt and Smewing, 1990; Cooper et al., 2014). The southern edge of what is now the Musandam Peninsula represents a major oblique-rifted (trans-tensional) off-set along this margin (Robertson et al., 1990). The Musandam formed a promontory to the north, with a SE-facing re-entrant facing the Hawasina Basin, now represented by the Dibba Zone. The platform edge then turned towards the south (Boote et al., 1990). Thermal subsidence of the NE Arabian plate led to a widespread transgression in the Wordian and the establishment of broad carbonate platform across the eastern Arabian plate - the Khuff Formation the subsurface Arabian Gulf and Saudi Arabia,

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the Saiq Formation of the central Oman Mountains. A stable carbonate platform was established in the Musandam area by at least the Late Permian, represented by the Bih Formation of the Rus Al Jibal Group, the base of which is nowhere exposed, and this persisted until the early Late Triassic through the Hagil and Ghail Formations. (Glennie et al., 1974; Blendinger et al., 1990; Rabu et al., 1993; Pillevuit et al., 1997; Styles et al., 2006; Maurer et al., 2007, 2009; Chauvet et al., 2009). Similarly, Late Permian patch-reefs developed on rifted fault blocks in the Dibba Zone area of the Hawasina Basin that, uniquely in the Oman Mountains, preserve an early Palaeozoic continental substrate (the Jabal Qamar thrust sheets, Hudson et al., 1954b; Glennie et al., 1974, Robertson et al., 1990). The sedimentology of the Rus Al Jibal Group shows a transition to more open shelf environments towards the presumed shelf edge (Styles et al., 2006), and we have observed the development of peloidal and oolitic packstones in the southern exposures of the Ghail Formation in the Wadi Bidi area, and Permo-Triassic shelf-margin sequences along the rather inaccessible mountains halfway up the east coast of Musandam. Similarly, Permian and Triassic slope sediments akin to those of the Sumeini Group exposed in northern Oman are not exposed. Coeval margin-proximal sediments of the adjacent Hawasina Basin (Dibba unit of the Hamrat Duru Group), dated to the Early and Middle Triassic (and possibly Late Permian), comprise platy lime mudstones, slump and intraformational breccias, calciturbidites and extrusive alkali basalts that show pronounced pillow elongation attributed to deposition on a submarine gradient, probably representing a base-of-slope environment (Cooper, 1986, 1990; Le Métour et al., 1992a). 8.2. The Kharas Formation as Late Triassic shelf-edge reef-related deposition (Figure 13b)

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A second major phase of Neo-Tethyan extension in the Oman sector took place between the Late Triassic and Early Jurassic (Glennie et al., 1974; Robertson, 1987; Béchennec et al., 1990, Rabu et al., 1993; Pillevuit et al., 1997). This was marked by localised volcanism in the Hawasina Basin and the development of very rapidly subsiding seamounts within the Hawasina Basin, such as Jabal Khaw in the south central Oman Mountains in which Later Triassic shallow-water limestone facies reach thicknesses in excess of 800m (Béchennec et al., 1986, 1990). Sedimentation patterns both on the platform and in the Hawasina Basin were also influenced by a global sea level lowstand that persisted for some 20 Ma from the later Norian into the Lower Jurassic (Hettangian) (Haq et al., 1988; Haq and Al-Qahtani, 2005). One result was that, along the Musandam segment of the platform, uplift linked to the early stages of renewed extension are represented by a sedimentary gap that spans much of the Carnian and Norian (Maurer et al., 2007). Siliceous shales and radiolarian cherts dominated deposition in the Hawasina Basin during this time (Béchennec et al., 1990; Bernoulli et al., 1990; Cooper, 1990) probably in part a result of reduced carbonate input leading to a raised CCD (calcite compensation depth). Subsidence in the ?Late Norian led to the resumption of sedimentation on the Musandam platform and deposition of the mainly peritidal Milaha Formation (Le Métour et al., 1992a; Maurer et al., 2007). An increased coarse-grained component to the limestones towards the SE, with the development of interbedded crossbedded grainstones (Phillips et al., 2006), suggests a more open shelf environment. Channelised limestone breccias and conglomerates were deposited in the upper part of the Milaha Formation immediately to the west of the Ausaq Bowl, where they are interbedded with mostly lime mudstones and grainstones. Similar calcirudites also

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form the base of the Kharas Formation on the west and northern sides of the Ausaq Bowl, where not eliminated by faulting. These point towards a period of margin instability with collapse along the shelf edge and the removal of the lower part of the Milaha Formation and upper part of the underlying Rus Al Jibal Group to the east of the Ausaq Bowl. A fore-reef talus wedge then evolved along that part of the shelf edge – the Kharas Formation. The varied facies of the Kharas Formation indicate the development of a sequence of reefs with abundant corals and calcisponges along the SE-facing edge of the Musandam platform, locally preserved in-situ in shelf-break sections a few kilometres north of Wadi Ausaq. The corals in the Kharas Formation are not in life position, but instead are concentrated in a fore-reef debris apron that also includes reworked clasts of finer-grained lagoonal lime mudstones and wackestones. Thick conglomeratic and breccia beds indicate continued instability along the shelf edge and the local failure along the edge of the reef complex. Abundant peloidal grainstones indicate the development of extensive shoals and sandbars from which debris was shed and transported along channels through the reef debris apron, or forming more laterally continuous beds, or percolating into the interstitial spaces in the reef debris. The development in the Late Triassic of the Kharas Formation along the southern side of the Musandam platform is, within the resolution of the biostratigraphic dating, coeval with the development of similar facies at Jabal Sumeini, 90 km to the south. Here, the Jabal Wasa Formation comprises massive cobble and boulder calcirudites (Glennie et al., 1974; Watts, 1990; Béchenec et al., 1993). They are found as a thrust sheet at a structurally low level in a major culmination of Sumeini Group predominantly slope facies sediments, having been detached from the allochthonous

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Mesozoic Arabian Plate margin units which, in this area are deeply buried beneath the Hawasina and Semail Ophiolite allochthon and Late Cretaceous-Cenozoic Aruma foredeep sediments. Unlike the in the southern Musandam platform area, the precise relationship between the Jabal Wasa Formation and the Mesozoic carbonate platform edge is not resolved in the Jabal Sumeini area. The major eustatic fall in sea-level at the end of the Triassic (Haq et al., 1988; Haq and Al-Qahtani, 2005) led to the progradation of siliciclastics eastwards across the Arabian Plate depositing quartz sandstones and shales onto the Musandam platform to form the Ghalilah Formation (Hudson, 1960; Glennie et al., 1974; Styles et al., 2006; Maurer et al., 2007). The terrigenous content of the Ghalilah Formation reduces to the SE (Phillips et al., 2006), but it reached the margin edge, with terrigenous sands locally incorporated into the Kharas Formation. 8.3. Jurassic Evolution of the Jarief Formation and Sumeini Group (Figure 13c) The effect of the continued sea level low stand and uplift linked to early-stage rifting of the proto-Indian Ocean means that uppermost Triassic and Early Jurassic sediments are notably absent from much of the Arabian plate (Ziegler et al., 2001), with erosion or non-deposition across most of Oman. The Musandam Peninsula is an exception, and deposition of the comparatively siliciclastic Ghalilah Formation continued into the Early Jurassic (Glennie et al., 1974; Maurer et al., 2007), prior to onset of deposition of the massive carbonate platform limestone sequences of the Musandam Group during the Hettangian (Styles et al., 2006). The apparent absence of Jurassic biota in the Kharas Formation, and the Middle Jurassic (Bathonian) dates derived from the overlying Sumeini Group and, at Jabal Agah, the Jarief Formation, suggests non-deposition or erosion of any Lower

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Jurassic sediments on the margin edge during this period. However, the effects of Late Cretaceous and Cenozoic folding and faulting mean the Musandam Formation is never seen in proximity to the Kharas Formation (Figure 1), and this relationship is not thus wholly resolved. The abrupt transition from the reef debris apron and grainstone shoals of the Kharas Formation to the by-pass slope lime mudstones with numerous intraformational truncation surfaces and slumps of the Sumeini Group suggests a rapid cut-off in coarser-grained sediment input. The precise reasons for this change are unclear, but factors may include a consequence of a coeval rise in sea level (Haq et al., 1988), consequential changes to the reefal fauna. The early Middle Jurassic also marked a period of comparatively increased tectonic activity along the Oman margin, associated with increased basin subsidence rates, most notably along the proximal parts of the Hawasina Ocean (Blechschmidt et al., 2004). This was marked by local siliciclastic input, preserved in particular in the Hamrat Duru Group of the southern Oman Mountains, and the development of slumps and mass flows. This impact was not equal across the shelf edge (Figure 13c). In the Jabal Agah area, thick peliodal and oolitic grainstone shoal deposits of the Jarief Formation accumulated during the Middle Jurassic (Bathonian-Callovian). This correlates with a period during which sedimentation along the edge of the Arabian platform was dominated by the development of oolitic shoals, now preserved as the coeval upper, informal oolitic member of the Sahtan Group in the Jabal Akhdar area of the central Oman Mountains (Rousseau et al., 2005). Oolitic shoal material was transport from the margin into the Hawasina Basin to form the characteristic oolitic and peloidal turbidite sequences of the Guwayza Formation of the Hamrat Duru Group (Glennie et al., 1974; Béchennec et al., 1990; Cooper, 1990; Blechschmidt et al., 2004).

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These are best-developed in the Dibba Zone in the coarse-grained margin-proximal Dibba structural unit of the Hamrat Duru Group. The coarse-grained sedimentation of the Jarief Formation in the Jabal Agah area ceased during the late Middle Jurassic or start of the Late Jurassic, with the deposition of lime mudstone-dominated successions of the Sumeini Group on a sloping sea-floor, recorded in the numerous intraformational truncation surfaces in the stratigraphic sequence. The western end of the southern side of the Musandam platform, along Batha Mahani (Figure 3), preserves a platform succession (where not destroyed by intensive quarrying) that indicates shallow-water sedimentation through the Jurassic (Phillips et al., 2006). This persisted until the Oxfordian. An unconformity separates the Musandam Group from the overlying Early Cretaceous Thamama Group, representing a period in the Late Jurassic of regional uplift and erosion along the margin of the Arabian platform possibly linked to the successful separation of the Indian plate from the SE edge of the Arabian plate (Loosvelt et al., 1996) and isostatic re-equilibrium of the shelf margin (Rousseau et al., 2005). Instability along the margin edge is recorded in a thick fining-upwards sequence of conglomerates and calci-turbidites that is developed at the top of the Guwayza Formation of the Hamrat Duru Group along the length of the Hawasina Basin. Late Jurassic uplift and associated normal faulting also affected the eastern margin of the Musandam Peninsula which appears to have acted as an emergent outer high to the Arab-Hith restricted carbonate-evaporite basin in the UAE (Robinson et al., 2006). However, there is less evidence in the margin proximal units of the Dibba Zone for destabilisation of the margin edge. There are no major conglomeratic or coarser-grained turbidite sequences of Upper Jurassic age in the Sumeini Group in this area, which continues to preserve fine-grained by-pass type margin

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sedimentation patterns. Similarly, there is only local evidence for a coarser-grained pulse at the top to the Guwayza Formation in the Hamrat Duru Group. 8.4. Latest Jurassic and Early Cretaceous Evolution of the Sumeini Group (Figure 13d) Stabilisation of the uplifted margin edge resulted in a marked reduction of carbonate production and transport into the Hawasina Basin and a concomitant rising of the CCD. This is recorded in the Oxfordian-Tithonian/ Barremian purple cherts and silicified limestones of the Huwar Formation of the Sumeini Group in the Jabal Sumeini and Jabal Qumayrah areas, 90 and 175 km south of the Dibba Zone respectively (Watts, 1990; Le Métour et al., 1992b; Béchennec et al., 1993; Cooper et al., 2012). Further out in the Hawasina Basin, this period correlates with an interval of brick red shales and radiolarian cherts in the lower part of the Sid’r Formation of the Hamrat Duru Group of the northern Oman Mountains (Cooper, 1986, 1990; Le Métour et al., 1992b; Béchennec et al., 1993). The Sumeini Group in the Dibba Zone is comparatively monotonous and does not contain a characteristic cherty interval equivalent to the Huwar Formation. Finegrained lime muds and silts continued to dominate the succession, although replacement chert nodules are present in the fine-grained section on Jabal Agah from which Tithonian ages have been obtained (Figure 11). This suggests the areas of deposition of the Sumeini Group in the Dibba Zone abutting the platform margin were comparatively shallow and largely remained above the CCD. Radiolarian cherts and silicified fine-grained limestones are developed in the Hamrat Duru Group, indicating the deeper continental rise of the Dibba Zone sector of the Arabian margin was below the CCD at this time (Cooper, 1990).

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On the platform close to the shelf margin, inversion and deepening of the shelf environment following the Late Jurassic uplift phase. A laterally variable thick conglomeratic interval along the southern side of the Musandam platform, the Batha Mahani Conglomerate of Styles et al. (2006), is dated as Valanginian and overlain by characteristic fine-grained porcellenous lime mudstones, which are correlated with Sahil Formation of the Oman Mountains. The succession in Batha Mahani ends with the deposition of very coarse-grained bioclastic limestones of Barremian age (Phillips et al., 2006). To the east and southeast, Sumeini Group sedimentation in the Dibba Zone during this time continued with little change, with the deposition of monotonous periplatform oozes and very thin turbidites on a steep slope environment, although biostratigraphic control is poor. 8.5. Ausaq Formation: early Late Cretaceous shelf edge collapse prior to foredeep development and ophiolite emplacement (Figure 13e) Passive margin sedimentation ended in the Cenomanian (Glennie et al., 1974; Searle et al., 1983, 1988a; Robertson 1987; Patton and O’Connor, 1988), concurrent with the formation of the Semail Ophiolite in an intra-Neo-Tethyan supra-subduction zone setting outboard of the Hawasina Basin (Tilton et al., 1981; Lippard et al., 1986; Le Métour et al., 1990; Warren et al., 2005; Rioux et al., 2012, 2013) that was most likely initiated by a change in the relative plate motions of Africa/ Arabia and Eurasia as a result of increased rifting and sea floor spreading in the South Atlantic (for example Dercourt et al., 1986; Glennie, 1995; Hooper et al., 1995; Loosveld et al., 1996; Sharland et al., 2001).

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Initial destabilisation of the Oman carbonate platform in this compressive regime resulted in regional mass wasting along the margin edge (Figure 13e, Figure 14). This is recorded in the thick, channelised and locally deeply down-cutting limestone breccias and conglomerates of the Ausaq Formation. Similar mass-wasting events are recorded in the major Sumeini Group culminations at Jabal Qumayrah 175 km to the south of the Dibba Zone, and Jabal Sumeini 90 km to the south (Robertson, 1987; Watts, 1990; Le Métour et al., 1991; Le Métour et al., 1992b; Cooper et al., 2012). This marks the transition to the deposition of the Muti Formation in the Hawasina Basin. The growth of a fore-bulge and flexural uplift, possibly through reactivation and inversion of pre-existing high-angle faults (Callot et al., 2010), raised the Arabian platform margin above sea level. This greatly reducing carbonate input into the Hawasina Basin before it foundered as the fore-deep ahead of the Semail subduction zone moved inboard towards the margin, resulting in the deposition of shale, radiolarian cherts and subordinate limestone debris flows and calciturbidites of the Muti Formation stratigraphically above both the Sumeini and Hamrat Duru Groups. The migration of the foredeep across the platform and prior to emplacement of the Hawasina-Haybi-Semail allochthon ended the distinctive margin-edge sedimentation patterns of the southern Musandam platform.

9. Conclusions The shelf margin to the Late Permian to Late Cretaceous Neo-Tethyan carbonate platform in Oman and the United Arab Emirates is not usually exposed as it is buried beneath a thick pile of thrust sheets. New biostratigraphic controls indicate that the Kharas Formation was deposited during the Late Triassic, and that the that the

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Kharas-Jarief-Sumeini units do not form part of the Late Cretaceous margin succession, as suggested by some earlier workers in the area. The Kharas Formation provides an insight into the development of a Late Triassic shelf-edge assemblage initiated during a period of Neo-Tethyan rifting and extension, on an eroded and unconformable contact with the underlying shallow-water and intertidal/ supratidal carbonate platform sediments of the Rus Al Jibal Group and Milaha Formation. It comprises a range of thick fore-reef talus deposits and peloidal lime sands. There is no unequivocal evidence for the preservation of Lower Jurassic units above the Kharas Formation. Instead, during the Middle Jurassic sea level highstand, fine-grained bypass-slope type lime mudstones of the Sumeini Group onlapped and draped the Kharas Formation along the southern edge of the Musandam platform. Large peloidal and oolitic shoals developed on the margin immediately to the south of the Musandam platform during the Middle Jurassic, now preserved as the Jarief Formation. These are coeval with the widespread deposition of ooid shoals on the platform and ooid-rich turbidites across the more marginproximal parts of the Hawasina Basin. The Jarief Formation was subsequently onlapped by Sumeini Group bypass-slope type lime mudstones, during the late Middle or Late Jurassic. Such slope sedimentation, characterised by numerous intraformational truncation surfaces persisted until the start of the Late Cretaceous, when the shelf edge and outer shelf/ proximal slope collapsed as a response to the onset of subduction within the Neo-Tethyan Ocean resulting in the deposition of the channelised Ausaq Formation mega-breccias. The area the foundered as the foredeep to the advancing Semail Ophiolite and associated Hawasina and Haybi thrust sheets moved towards and ultimately across the margin edge prior to final ophiolite obduction and emplacement during the Santonian.

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Acknowledgements We are grateful to the Petroleum Institute, Abu Dhabi for funding fieldwork and sample preparation. David Cooper also acknowledges previous funding of work in the Dibba Zone by the Natural Environment Research Council and Amoco Petroleum and thanks Deborah Rees for her assistance in the field and technical support. Mike Searle made very helpful suggestions on an earlier draft of this paper, and we are grateful to Alastair Robertson for his comments reviewing this paper.

References Allemann, F., Peters, T.J., 1972. The Ophiolite-Radiolarite Belt of the North Oman Mountains. Eclogae Geologicae Helvetiae, 65(3), 657-697. Baud, A., Béchennec, F., Cordey, F., Le Métour, J., Marcoux J., Richoz, S., 2001. Permo-Triassic Deposits: from Shallow Water to Base of Slope. International Conference Geology of Oman. Post-Conference Excursion No. B01 in the Oman Mountains, January 17 - 20, 48p. Baud, A., Bernecker, M., (Eds.) 2010. The Permian-Triassic transition in the Oman Mountains: transect of the Tethyan margin from shallow to deep-water deposits. IGCP 572 Field Guide Book 2, Gutech Geoscience Workshop Publication 1, 109p. Béchennec, F., Beurrier, M., Rabu, D, Hutin, G., 1986. Geological map of Bahla, Sheet NF 40-7A scale 1:100,000 with Explanatory Notes. Directorate General of Minerals, Oman Ministry of Petroleum and Minerals. Muscat. 36

Béchennec, F., Le Métour, J., Rabu, D., Bourdillon-Jeudy de Grissac, C., de Wever, P., Beurrier, M., Villey, M., 1990. The Hawasina nappes: Stratigraphy, palaeogeography and structural evolution of a fragment of the south Tethyan passive continental margin. In Robertson, A.H.F., Searle, M.P., Ries, A.C., (Eds.), The Geology and Tectonics of the Oman Region. Geological Society of London, Special Publication 49, 213-223. Béchennec, F., Roger, J., Le Métour J., Janjou, D., 1993. Geological map the Al Sumayni Quadrangle, Sheet NG 40-14A4 scale 1:50,000 with explanatory notes. Directorate General of Minerals, Oman Ministry of Petroleum and Minerals, Muscat. Bernoulli, D., Weissert, H., Blome, C.D., 1990. Evolution of the Triassic Hawasina Basin, Central Oman Mountains. In Robertson, A.H.F., Searle, M.P., Ries, A.C., (Eds.), The Geology and Tectonics of the Oman Region. Geological Society of London, Special Publication 49, 189-202. Biehler, J., Chevalier, C. Ricateau, R., 1975. Geological map of the Musandam Peninsula, Sultanate of Oman. Directorate of General Petroleum and Minerals, Sultanate of Oman. Blechschmidt, I., Dumitrica, P., Matter, A., Krystyn, L., Peters, T., 2004. Stratigraphic architecture of the northern Oman continental margin – Mesozoic Hamrat Duru Group, Hawasina Complex, Oman. GeoArabia, 9(2), 81-132. Blendinger, W.A., Van Vliet, A., Hughes-Clarke, M.W., 1990. Updoming, rifting and continental margin development during the late Palaeozoic in northern Oman. In Robertson, A.H.F., Searle, M.P., Ries, A.C., (Eds.), The Geology and Tectonics of the Oman Region. Geological Society of London, Special Publication 49, 27-37. Boote, D.R.D., Mou, D., White, R.I., 1990. Structural evolution of the Suneinah foreland, central Oman Mountains. In Robertson, A.H.F., Searle, M.P., Ries, A.C., (Eds.), The

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Le Métour, J., Béchennec, F., Roger, J., Wyns, R., 1991. Geological map of Dank, Sheet NF 40-2B scale 1:100,000 with Explanatory Notes. Directorate General of Minerals, Oman Ministry of Petroleum and Minerals. Muscat. Le Métour, J., Béchennec, F., Wyns, R., 1992a. Geological map of Musandam and Mudha, Sheet NF 40-06/10 scale 1:250,000 with Explanatory Notes. Directorate General of Minerals, Oman Ministry of Petroleum and Minerals. Muscat. Le Métour, J., Béchennec, F., Chevremont, P., Roger, J., Wyns, R., 1992b. Geological map of Buraymi, Sheet NF 40-14 scale 1:250,000 with Explanatory Notes. Directorate General of Minerals, Oman Ministry of Petroleum and Minerals. Muscat. Lippard, S.J., Shelton, A.W., Gass, I.G., 1986. The Ophiolite of Northern Oman. Blackwell Scientific Publications, Oxford, 178p. Loosveld, R.J.H, Bell A., Terken, J.J.M., 1996. The tectonic evolution of interior Oman GeoArabia, 1(1), 28-51. Maurer, F. Rettori, R., Martini, R., 2007. Triassic stratigraphy, facies and evolution of the Arabian shelf in the northern United Arab Emirates. International Journal of Earth Sciences 97(4), 765-784. Maurer, F., Martini, R., Rettori, R., Hillgärtner, H., Cirilli, S., 2009. The geology of Khuff outcrop analogues in the Musandam Peninsula, United Arab Emirates and Oman. GeoArabia, 14(3), 125-158. Mulder, T., Alexander, J., 2001. The physical character of subaqueous sedimentary density flows and their deposits. Sedimentology, 48, 269-299. Nolan, S.C., Skelton, P.W., Clissold, B.P., Smewing, J.D., 1990. Maastrichtian to early Tertiary stratigraphy and palaeogeography of the central and northern Oman mountains. In Robertson, A.H.F., Searle, M.P., Ries, A.C., (Eds.), The Geology and

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Rioux, M., Bowring, S., Kelemen, P., Gordon, S., Miller, R., Dudás, F., 2013. Tectonic development of the Samail ophiolite: High-precision U-Pb zircon geochronology and Sm-Nd isotopic constraints on crustal growth and emplacement, Journal of Geophysical Research Solid Earth, 118, 1-17, doi:10.1002/jgrb.50139. Robinson, A., Searle, M.P., Toland, C., 2006. Field guide: Musandam Field Seminar, 16-18 January 2006. Oolithica Geosciences Ltd. Robertson, A.H.F., 1987.The transition from a passive margin to an Upper Cretaceous foreland basin related to ophiolite emplacement in the Oman Mountains. Geological Society of America Bulletin, 99(11), 633-653. Robertson, A.H.F., Searle, M.P., 1990. The northern Oman Tethyan continental margin: Stratigraphy, structure, concepts and controversies. In Robertson, A.H.F., Searle, M.P., Ries, A.C., (Eds.), The Geology and Tectonics of the Oman Region. Geological Society of London, Special Publication 49, 3-25. Robertson, A.H.F., Blome, C.D., Cooper, D.J.W., Kemp, A.E.S, Searle, M.P., 1990. Evolution of the Arabian continental margin in the Dibba Zone, Northern Oman Mountains. In Robertson, A.H.F., Searle, M.P., Ries, A.C., (Eds.), The Geology and Tectonics of the Oman Region. Geological Society of London, Special Publication 49, 251-284. Rousseau, M., Dromart, G., Garcia, J-P., Atrops, F., Guillocheau, F., 2005. Jurassic evolution of the Arabian carbonate platform edge in the central Oman Mountains. Journal of the Geological Society, London, 162, 349-362. Searle M.P., 1988a. Thrust tectonics of the Dibba zone and the structural evolution of the Arabian Continental margin along the Musandam mountains (Oman and United Arab Emirates). Journal of the Geological Society, 145, 43-54.

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EVOLUTION OF THE ARABIAN CONTINENTAL MARGIN OF THE NORTHERN DIBBA ZONE, EASTERN UNITED ARAB EMIRATES AND OMAN David J.W. Cooper, Christopher Toland, Mohammed Y. Ali and Owen Green

FIGURE CAPTONS

Figure 1. Geological map of the Musandam Peninsula, Dibba Zone and northern Oman showing the main lithological units, compiled from various sources including Glennie et al. (1974), Beihler et al. (1975), Le Métour et al. (1992), Styles et al. (2006) and Searle et al. (2014).

Figure 2. (a) The Musandam margin as part of the Arabian Neo-Tethyan passive margin, modified from Sharland at al. (2001). (b) Reconstruction of the Hawasina basin (Middle Jurassic) showing the southern edge of the Musandam platform and Dibba Zone as an oblique rifted margin, modified from Searle et al. (1983), Cooper, (1990) and Robertson et al. (1990). (c) Schematic cross-section through the Late Permian-Mesozoic carbonate platform, slope and deeper-water units, showing the broad tectono-stratigraphic units that are recognised in the Dibba Zone, modified from Searle et al. (1983, 2014).

Figure 3. Stratigraphic relationships between the Hajar Supergroup, Kharas Formation, Jarief Formation, Sumeini Group and Ausaq Formation along the southern edge of the Musandam platform and the northern edge of the Dibba Zone, and at Jabal Agah. Geological map with additional information from Glennie et al. (1974), Searle et al. (1983a, b), Searle (1988), Robertson et al. (1990), Le Métour et al. (1992) and Styles et al. (2006). A, B etc show lines of cross-sections in Figure 4.

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Figure 4. Cross-sections through the boundary between the Musandam platform and Dibba Zone, showing the distribution of the Kharas and Jarief Formations, Sumeini Group and Ausaq Formation.

Figure 5. Map and cross-sections through the Jabal Agah anticline, showing the outcrop of the Jarief Formation. (NB colour of the Kharas Formation is different from the other maps, for clarity). Divisions within the Sumeini Group are informal.

Figure 6. Field photographs of the Kharas Formation. (a) Gorge through Kharas Formation showing typical joint-controlled outcrop weathering, Musandam dip slope north side Ausaq bowl. (b) Poorly-defined bedding in faulted and jointed Kharas Formation, Musandam dip slope north side Ausaq bowl. (c) Massive, jointed but otherwise structureless Kharas limestones, Wadi Laqras gorge. The cliff is approximately 100m high. (d) Mountain forming Kharas Formation (Kh) over Rus Al Jibal limestones (RaJ) with a local veneer of fine-grained Sumeini Group limestones (S). Foreground comprises intensely folded silicified limestones and cherts of the Hamrat Duru Group (HD). (e) Fault-bound Kharas Formation (Kh) along the central axis of the Jabal Agah anticline. (J) Jarief Formation, (Sum) Sumeini Group. (f) Kharas Formation outcrop in the northern Jabal Agah.

Figure 7. Close-ups of the Kharas Formation. a) Typical weathering of Kharas Formation masking all internal structures. North side Khabb bowl. (b) Boulder from Kharas Formation (not in situ) showing recrystallized coral-rich rudstone in irregular contact with coarse-grained peliodal packstone. North side Khabb bowl. (c) Irregular

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clasts of recrystallized peloidal shelly coral wackestones in a coarse wackestone matrix with angular granule-fine pebble grade clasts. North side Ausaq bowl. (d) Recrystallised shelly coral rudstone with numerous clasts of peloidal wackestones containing abundant broken shell debris. North side Ausaq bowl. (e) Recrystallised poorly-sorted rudstone with large broken coral debris and voids rimmed with fibrous calcite infilled with lime mudstone and wackestones. Jabal Agah. (f) Poorly-sorted irregular rudstone/ locally floatstone. Clasts comprise mainly lime mudstones, wackestones and packstones. Numerous irregular voids rimmed with fibrous calcite and infilled with lime mudstone. Jabal Agah.

Figure 8. (a) Contact between Kharas Formation and underlying Rus Al Jibal Group, Musandam dip slope north side Ausaq bowl. (b) Irregular contact between Kharas Formation and underlying Rus Al Jibal Group, Musandam dip slope looking SE into the Ausaq bowl. (c) Sumeini Group (grey, smoother-weathering) in irregular stratigraphic contact with the Kharas Formation (browner, heavily jointed), from col 2 km NE of Satkha village. (d) Close-up of irregular stratigraphic contact between the Kharas Forman (brown) and Sumeini Group (grey), Wadi Laqras.

Figure 10. Jarief Formation: field photographs. (a) View over the Jarief Formation along the western side of the plateau crest of the Jabal Agah anticline. (b) Thickbedded grainstones and packstones of the Jarief Formation exposed at the faulted end of the northern part of the Jabal Agah plateau. (c) Laminated and dune-bedded recrystallized grainstone. (d) Thick-bedded structureless grainstone/ packstone with a pebbly basal unit amalgamated with the underlying packstone. Pebbles comprise intraformational packstones and lime-mudstone.

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Figure 9. (1) Photomicrographs from the Kharas Formation (a) Galeanella cf. tolmanni, sample 7/228B (b) Galeanella cf. tolmanni, sample 7/229C (c) Muranella sphaerica, sample 7/229C (d) Alpinophragmium perforatum, sample 7/241A (e) Triasina hantkeni (centre) and Radiomura cautica (upper left), sample 7/276D (f) Microtubus communis, sample 7/240D (g) Aeolisaccus inconstans, sample 7/276D (h) Dusotominid cf D. turboidea, sample 7/276A. (2) Photomicrographs from the Jarief Formation (i) Meyendorfina bathonica, sample 7/276E (j) Mohlerina basiliensis, sample 7/276e (k) Redmondoides lugeoni, sample 7/276E (l) Meyendorfina bathonica, sample 7/276F (m) (?Prae-)Kurnubia sp, sample 7/277B (n) ?Riyadhellid foraminifera, Sample 7/276F (o) Rivularia lissaviensis, sample 7/279D (p) Dendroid stromatoporoid (?Shuqraia sp), sample 7/279D. (3) Photomicrographs from the Sumeini Group (q) Praetintinopsella andrusovi, sample 7/274B (r) Redmondoides rotundatus, sample 7/227A (s) Nautiloculina cf. oolithica, sample 7/271B (t) Gemeridella minuta, sample 7/274B (u) Crustocadosina semiradiata olzae, sample 7/274B (v) cf. Mesoendothyra croatica, sample 7/227A (w) Commitosphaera pulla, sample 7/274B (x) Aeolisaccus dunningtoni, sample 7/274B.

Figure 11. Stratigraphic section through the Kharas-Jarief-Sumeini and Ausaq of Jabal Agah (see Figure 5), with illustrative photographs. Note change of scale for the Kharas and Jarief Formations. Divisions within the Sumeini Group are informal.

Figure 12. Photographs of the Sumeini Group and Ausaq Formation. (a) Sumeini Group: very fine grained parallel laminated lime mudstone with argillaceous partings.

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Jabal Agah. (b) Sumeini Group: graded fine-grained to lime mudstone bed with climbing ripples passing upwards into parallel laminations with subordinate ripples. The top of the bed is bioturbated with an irregular replacement chert band. The micrite top of the underlying bed has also been silicified along the boundary with an argillaceous parting. Jabal Agah. (c) Sumeini Group: finely-graded lime mudstone with the upper part of beds heavily bioturbated and argillaceous. (d) Sumeini Group: 100 m scale channel in the lower part of the Group about 30 m above the contact with the Kharas Formation. Tr-intraformational truncation surface defining main channel. C-0-1.5 m channelled grainstone. NW side Khabb Bowl. (e) Ausaq Formation: Ausaq conglomerates cutting down into fine-grained Sumeini Group limestones, Ausaq gorge. Skyline trees are about 3 m high. (f) Ausaq Formation: rafts of Sumeini Group limestone in a cobble/ boulder matrix derived from the Hajar Supergroup shelf succession, Kharas Formation and Sumeini Group. NW end of Khabb Bowl. Bush (centre middle) is about 3 m high. (g) Ausaq Formation: close-up showing abundant chert clasts. These are not seen in the Kharas Formation conglomerates. J Agah. (h) Field photograph showing a thin (up to 5 m) veneer of Ausaq Formation conglomerates over the Sumeini Group (Sum), conformably overlain by shales, silicified limestones and cherts of the Muti Formation (Riy Riyamah member). South side Jabal Yaweed.

Figure 13. Evolution of the southern part of the Musandam peninsula. See text for discussion.

Figure 14. Diagram showing the relationships between the Kharas Formation, Sumeini Group and Ausaq Formation and the Musandam platform succession along

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the central section of the southern edge of the Musandam platform in the Ausaq bowl area. It is compared with the stratigraphic units of the interior Musandam platform. Not to scale.

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Microtubus communis (microproblematica: Carnian-Norian) Muranella sphaerica (microproblematica: long-ranging, undiagnostic) Tubiphytes obscurus (microproblematica: no younger than Rhaetian) Galeanella cf tolmanni foraminifera (unequivocal specimens of the Late Triassic) Alpinophragmium perforatum (encrusting foraminifer: Norian-Rhaetian) Bacanella floriformis (algae: mid to Late Triassic) Uvanella sp. (sphinctozoan sponge: Late Triassic) Duostominid foraminifera (poorly preserved: Late Triassic) Spongiostromate crusts

OM13-7/276E and F

OM13-7/279D

Nautiloculina sp. (benthic foraminifera)

Meyendorffina bathonica (benthic

Redmondoides lugeoni (benthic

foraminifera)

foraminifera)

Praekurnubia crusei (benthic foraminifera)

Meyondorffina bathonica (benthic

Andersenolina (Trocholina)

foraminifera)

palastiniensis (benthic foraminifera)

Mohlerina basiliensis (shallow-water

Rivularia sp. (calcareous algae)

trochospiral benthic foraminifera)

Redmondoides lugeoni (benthic

Rivularia lissaviensis (calcareous algae)

foraminifera)

?Praekurnubia sp. (benthic foraminifera)

Dasyclad alga cf. Salpingoporella

Stromatoporoid (Shuqraia sp or

Stromatoporoid debris

53

Promillepora sp) Age: late Middle to Late Callovian

Indeterminate small textulariid foram cf. Riyadhellid Gastropod, coral Coarsely agglutinated foraminifera Age: Middle Bathonian to Callovian

Sumeini Group: lower part: Khabb bowl Redmondoides rotundatus (benthic foraminifera) Nautiloculina cf. oolithica (benthic foraminifera) ? Mesoendothyra croatica (benthic foraminifera) R. rotundatus is indicative of the Mid-Late Bathonian

Sumeini Group: above Jarief Formation: Jabal Agah Aeolisaccus dunningtoni (benthic foraminifera) Praetintinopsella andrusovi (calpionellid) Commitosphaera pulla (calcareous dinocyst) Gemeridella minuta (microproblematica) Crustocadosina semiradiata olzae (calcareous dinocyst) Implies Late Tithonian

54

EVOLUTION OF THE ARABIAN CONTINENTAL MARGIN OF THE NORTHERN DIBBA ZONE, EASTERN UNITED ARAB EMIRATES AND OMAN David J.W. Cooper, Christopher Toland, Mohammed Y. Ali and Owen Green

TABLE CAPTONS Table 1. Fauna and flora from the Kharas Formation. See also photomicrographs in Figure 9a-h.

Table 2. Fauna and flora from the Jarief Formation. See also photomicrographs in Figure 9i-p.

Table 3. Fauna and flora from the Sumeini Group. See also photomicrographs in Figure 9q-x.

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Graphical abstract

EVOLUTION OF THE ARABIAN CONTINENTAL MARGIN OF THE NORTHERN DIBBA ZONE, EASTERN UNITED ARAB EMIRATES AND OMAN

David J.W. Cooper, Christopher Toland, Mohammed Y. Ali and Owen Green

Highlights 

A new model for the evolution of the south Musandam part of the Arabian NeoTethyan shelf-edge.



New biostratigraphic data resolve previous Late Triassic/ Late Cretaceous dating ambiguities.



Documenting the transition through time from carbonate platform to by-pass slope facies.