A. Leslie

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Field

Geology of the Umm Azzimul 1:100 000 map sheets 100-10 &-100-15, United Arab Emirates

Andrew Farrant Colm Jordan A. Leslie J.E. Merritt J.W. Merritt

This Sheet Description describes the Quaternary and solid geology of the Umm Azzimul 1:100 000 scale geological map. The Umm Azzimul district covers approximately 2700 km2 in the far southeast of the UAE along the border with Saudi Arabia and Oman. This district spans the transition from the extensive sand sea of the Ramlat ar Rabbad in the northwest to the distal alluvial fan sediments and Miocene limestone outcrops along the border with Oman around Al Manadir and Umm Azzimul, and includes the eastern extension of the Liwa megabarchan field. The oldest rocks in the area are the Miocene Dam Formation limestones and dolomites that form flat or very gently sloping limestone pavements within the interdunes in the far southeast of the district. In the northeast, these are partially overlain by the fluvial sands and gravels of the Hili Formation. These fluvial gravels represent the very distal end of a large alluvial fan system that extends out from the Hajar Mountains. The lithological composition of these gravels reflects their source area in the Hamrat Duru region of Oman, rather than the ophiolite source seen further north. These alluvial fans peter out in a series of continental sabkhas underlain by both fluvial and aeolian sands. The major part of the Umm Azzimul district consists of aeolian dunes of various morphologies. The dune morphology changes systematically in a south and south-easterly direction across the district, reflecting the migration of the dunes driven by the prevailing wind. In the northwest, the extensive Ramlat ar Rabbad sand sea is comprised of large barchan dunes that get progressively smaller to the south and east. Across the central part of the district, these morph into more discrete megabarchan dunes and dune ridges separated by flat interdune sabkhas. Much of the south-western part of the sheet is occupied by large crescentic megabarchan dunes up to 130 m high that extend west into the Liwa area, whilst in the east, the elongate linear dune ridges, punctuated by numerous star dunes and occasional megabarchans are more common. The star dunes become more frequent close to the Oman border. These dune ridges and star dunes can rise up to 100 m above the surrounding interdunes. Most of the district is sparely populated, with no major urban areas and few roads. The south of the region is also host to the relatively small Qusawira and Mender oilfields.

Outcrop

Alluvial fan

Alluvial plain

Source

Cite

Citations (0)

Geology of the Al Hamra 1:100 000 map sheet, 100-14, United Arab Emirates

J.W. Merritt Andrew Farrant J.E. Merritt Colm Jordan Simon Price

This Sheet Description describes the Quaternary geology of the Al Hamra 1:100 000 scale geological map. About 70 observation points were made throughout the Al Hamra district, which covers 2500 km2 of country in the south-east corner of the UAE. No pre-Quaternary bedrock exposures were identified in the district, which contains a variety of active, aeolian sand deposits in different morphological forms, including fields of high barchans, sand sheets and low dunes. High dune ridges separated by elongate sabkha pans extend a few kilometres westwards across the eastern boundary of the sheet. Madinat Zayed Formation (MZ) aeolianites crop-out within small, deep interdune hollows within the extensive sand sea that dominates most of the district. The area has no known economic mineral deposits.

Sabkha

Bedrock

Source

Cite

Citations (0)

Geology of the Al Qua’a 1:100 000 map sheet, 100-9, United Arab Emirates

Andrew Farrant S.J. Price J.E. Merritt J.W. Merritt A. Leslie

This Sheet Description describes the Quaternary and solid geology of the Al Qua'a 1:100 000 scale geological map. The Al Qua'a district covers approximately about 1750 km2 in the southeast of the UAE along the border with Oman. This district spans the transition from the extensive sand sea of the Ramlat ar Rabbad in the west to the distal alluvial fan sediments of the Hili Formation along the border with Oman. The oldest rocks in the area are the fluvial sands and gravels of the Hili Formation, which probably overlie the Miocene Dam Formation at shallow depth. They represent the distal end of a large alluvial fan system that extends from the Hajar Mountains. Two distinct gravel units are recognised, reflecting different source areas. One comprises clasts derived largely from the Hamrat Duru Group rocks of Oman, whereas the second includes a more heterogeneous combination including Hamrat Duru and Oman-UAE ophiolite clasts. The alluvial fans pass into continental sabkhas underlain by distal fluvial sediments and deflated aeolian sand. In the far northwest, palaeodune sandstones of the Madinat Zayed Formation occur within some of the interdunes. The major part of the district consists of aeolian dunes which change in morphology in a south and south-easterly direction across the district. In the west, the low barchan dunes along the eastern fringe of the extensive Ramlat al Rabbad sand sea merge into more discrete elongate dune ridges separated by flat interdune sabkhas. These dune ridges are punctuated by mega-barchans and star dunes that rise up to 100 m above the surrounding interdunes.

Alluvial fan

Source

Cite

Citations (0)

Geology of the Al Wathba 1:100 000 map sheet, 100-12, United Arab Emirates

Andrew Farrant R.A. Ellison A. Leslie Andrew Finlayson R.J. Thomas

This Sheet Description describes the Quaternary and bedrock geology of the Al Wathba 1:100 000 scale geological map. The district covers 2780 km2 southeast of Abu Dhabi island, and includes many of the suburbs of Abu Dhabi city, including the proposed Capital District, Madinat Khalifa A and B, Mussafah, Mohammed bin Zayed City, Mafraq, Bani Yas, Al Wathba, Al Falah, Al Shamka and Abu Dhabi International Airport. The sheet extends east as far as Al Khatim. The pre-Quaternary bedrock comprises Miocene evaporitic mudstone and siltstone of the Gachsaran Formation (Fars Group) overlain by the dolomitic conglomerates, sandstones and siltstones of the Barzaman Formation in the north. In the south and west, the Gachsaran Formation is overlain by the dolomites and limestones of the Dam Formation which forms an escarpment around the Al Dhafra Air Base. These are overlain by the sandstones of the Shuwaihat and Baynunah Formations. Borehole evidence suggests there is a gradation from interbedded siltstones and sandstones of the Baynunah Formation in the west of the district to coarse dolomitic conglomerates of the Barzaman Formation in the north. The Miocene rocks are locally overlain by fluvial sandstones and channel gravels of the Hili Formation which represent Quaternary outwash from the Hajar Mountains to the east. Much of the region is partially covered by pale carbonate aeolianites of the Ghayathi Formation, themselves often covered in a veneer of more recent aeolian sand. These are well exposed near the coast in spectacular zeugen and inland, they form a series of east-northeast trending linear ridges. Modern pale carbonate-dominated low dunes occur particularly in the west of the district. The coastal zone is dominated by a range of Late Pleistocene to Holocene littoral and marine deposits, which comprise the Abu Dhabi Formation. These include coastal spits and bars, algal mats, mangrove swamps and intertidal sediments. Sabkha is developed on the surface of these deposits. The region has seen major development over the past 30 years, which has radically changed the surface geology. Much of the coastal strip has been reclaimed or developed, with a variable amount of made ground, often composed of carbonate sand dredged from the neighbouring lagoons. Further inland, many areas have been extensively landscaped, with large areas of dunes levelled flat or quarried for fill. Much of the north-western part of the sheet is either developed or scheduled for development. Extensive areas of forestry occur along the line of the main Abu Dhabi – Al Ain highway and north of Abu Dhabi International Airport.

Conglomerate

Bedrock

Escarpment

Source

Cite

Citations (2)

Geology of the Al Lisaili 1:100 000 map sheet, 100-6, United Arab Emirates

Andrew Farrant S.J. Price Sarah Arkley Andrew Finlayson R.J. Thomas

This Sheet Description describes the Quaternary and solid geology of the Al Lisaili 1:100 000 scale geological map. It includes the southern outskirts of Dubai, including part of Jebal Ali and the development around the new Al Maktoum International Airport. Apart from these urban areas, the region is largely undeveloped desert. Much of the map area is covered by dune forms, mostly either low dunes or dune ridges, with large interdunes underlain either by variably dolomitised sandstone, siltstone and conglomerate of the Miocene Barzaman Formation or the Quaternary fluvial sandstones, conglomerates and calcretes of the Hili Formation. The Barzaman Formation forms the rock-head across most of the district and is locally well exposed in interdunes. Quaternary carbonate-dominated aeolianites (Ghayathi Formation) form distinctive palaeodune ridges that trend southwest-northeast-across the district, particularly to the west and northwest of the district. Marine deposits of the Abu Dhabi Formation are present around Jebal Ali, mostly forming areas of coastal sabkha. Although the majority of sheet 100-6 is desert, significant parts of the onshore landscape and the short stretch of coast has been strongly influenced by anthropogenic activity. The rapid growth of Dubai since the 1970s has led to extensive areas being landscaped or reclaimed for development or forestry. Major residential, commercial and industrial developments exist or are proposed around Jebal Ali, and around the Al Maktoum International Airport, whilst forestry and farming projects occur in the south and west. Many of the excavations in the development sites around Dubai and Jebal Ali, such as for example, the trial excavations for the proposed Arabian Canal scheme, provided excellent exposures of the underlying geology. Details of some of these sections are provided in this report. Over much of the area, ‘Made Ground’ that includes engineered fill is widespread.

Sabkha

Conglomerate

Source

Cite

Citations (5)

Geology of the Asab 1:100 000 map sheet, 100-18, United Arab Emirates

J.W. Merritt R.J. Thomas Andrew Farrant Simon Price Colm Jordan

This Sheet Description describes the Quaternary geology of the Asab 1:100 000 scale geological map. About 110 observation points were made throughout the district, which covers 2500 km2 of country that includes the northernmost part of the Liwa crescent oasis. No pre-Quaternary bedrock exposures were identified in the district, which contains a variety of active, aeolian sand deposits in different morphological forms, including fields of high barchans, sand sheets and low dunes. The Liwa mega-barchan field lies in the south-western corner of the district, with its associated hard-surfaced, whitish sabkha pans. The Madinat Zayed and Ghayathi Formation aeolianites crop-out within small, deep interdune hollows within the extensive sand sea that dominates most of the south-eastern half of the district. The Madinat Zayed Formation also forms sparse, low mesas within the interdunes of the Liwa mega-barchan field. Apart from the Asab oilfield, the area has no economic mineral deposits.

Bedrock

Sabkha

Source

Cite

Citations (0)

Geology of the Sahil 1:100 000 map sheet, 100-17, United Arab Emirates

J.W. Merritt J.E. Merritt R.J. Thomas Andrew Farrant Andrew Finlayson

This Sheet Description describes the Quaternary and solid geology of the Sahil 1:100 000 scale geological map of the UAE. The Sahil district covers 2500 km2 of the country stretching inland from the coastal sabkha. The land rises from 10 m above sea level on the coastal plain in the northwest to over 100 m in the southeast. Miocene bedrock crops out beneath the northern half of the district, forming isolated jebals up to about 30 m high within fields of low barchanoid dunes, and underlying intervening interdunes or small sabkhas. The oldest rocks in the area are the Miocene rocks of the Dam, Shuwaihat and Baynunah formations. The Dam Formation comprises pale grey, fine grained carbonates and nodular gypsum beds which crop at low elevations within and around the margins of the coastal sabkha. The overlying Shuwaihat Formation is characterised by red sandstones with subordinate green mudstones and grey pedogenic beds laid down in a mixed aeolian-fluvial-sabkha environment. It is overlain by the Baynunah Formation which has a characteristic basal bone bed with an erosive base. Above is a sequence of interbedded calcareous siltstones, siltstones and fine sandstones, laid down in a low-energy fluvio-lacustrine system (Barakah and Hamrah members), capped by reddish brown, playa or lacustrine sandstones (Sahil Member). Miocene deposits are overlain unconformably by Quaternary deposits of the Madinat Zayed Formation: quartz dominated, cross bedded aeolianite and lacustrine siltstone, and the Ghayathi Formation: moderately cemented, carbonate dominated aeolianite. Much of the district has a cover of unconsolidated aeolian sand either as a thin veneer within the interdunes and coastal sabkhas or as extensive low barchanoid dune fields, sand sheets and dune ridges. The northern part of the district includes part of the coastal sabkha, which is largely underlain by deflated unconsolidated quartzose aeolian sand and the calcareous Ghayathi Formation aeolianite.

Sabkha

Siltstone

Bedrock

Marl

Source

Cite

Citations (0)

Geology of the Al Khatam 1:100 000 map sheet, 100-13, United Arab Emirates

Andrew Farrant A. Leslie J.E. Merritt J.W. Merritt Colm Jordan

This Sheet Description describes the Quaternary and solid geology of the Al Khatam 1:100 000 scale geological map. The Al Khatam district covers 2780 km2 southeast of Abu Dhabi. Most of the area is underlain by Quaternary aeolian and fluvial deposits, but the underlying Miocene bedrock outcrops in the northeast of the district. These comprise fluvial sandstones of the Baynunah Formation which probably underlie much of the district. These Miocene rocks are poorly exposed in roughly northwest to southeast trending inter-dune areas in the north-western corner of the district. It is possible the Barzaman Formation underlies the dunes in the north-east but it is not exposed at surface in this district. Over almost the entire area, the Miocene rocks are overlain by Quaternary deposits. These consist predominantly of weakly cemented calcareous quartzose aeolian sandstones of the Madinat Zayed Formation. These crop out within large interdunes throughout the district, and locally form small mesas or terraces. To the northeast, the aeolian sandstones of the Madinat Zayed Formation grade into the predominantly fluvial sandstones and conglomerates of the Hili Formation. These fluvial sandstones represent the distal end of a complex alluvial fan system draining from the Hajar Mountains in the east. As such, they tend to fine distally to the southwest, where the majority of the fluvial sands and siltstone/mudstones occur. They locally contain intercalated aeolian sand beds which were blown in from the north-west. Quaternary carbonate aeolianites of the Ghayathi Formation occur locally in the northern part of the district. These represent fossil calcareous palaeodune systems which locally form the cores to the modern carbonate-dominated dune ridges. The Quaternary deposits are overlain by more recent unconsolidated dune sands with various morphologies, mapped as low dunes, dune ridges, sand sheets and barchanoid dune fields. These cover most of the area and are arranged into a series of west-northwest to east-southeast trending dune fields. In the northeast of the district, nearest the coast, these dunes sands are predominantly carbonate, but they get progressively more quartzose to the southeast. The interdune areas, floored either by Miocene or Quaternary sediments, are often masked by sabkhas or thin veneers of aeolian dune sand.

Outcrop

Bedrock

Alluvial fan

Siltstone

Source

Cite

Citations (1)