Geology of Qatar 2015

8/19/2019 Geology of Qatar 2015

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Geology of Qatar

Short Introduction


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Introduction

•

Qatar is a peninsula with anapproximate area of 11610square kilometers.

• The topography of the country ingeneral is a deflation surfaceshaped by the persistent Shamalwind except some low hills in theNorth West.

• The surface topography ischaracterized generally by lowrelief ranging from around 103 mabove sea level in the southwestto nearly 6 m below sea level inDukhan sabkha.

• The majority of the country,however, is less than 40 m abovesea level.


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Topographic features: Sand dunes

• Sand dunes are the mostprevalent form of sandaccumulation in thecountry.

• Some of them are isolatedindividuals but barchansalso occur containinglongitudinal are reversedunes.

• Sand dune fields can be

found in the southeastcovering around 10% of thetotal area of the country aswell as in the southwesternareas.


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Topographic features: Coastal sediments

• Coastal sediments are

these sediments

associated with the

shallow marineenvironment and

resulted from the

combined effect of

accumulation anderosion.


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Surface Geology

• The surface geology ofQatar is covered by twocontrasting lithologicalregimes; carbonates andclastics.

• The Mio-Pliocene andPleistocene strata areformed of clasticmaterials while the rest

are formed of carbonatesediments and strata.

• .


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Hofuf Formation

• The Hofuf Formationrepresents the youngestNeogene deposits in theQatar Peninsula and

forms about 3 % of theexposed rocks.

• The Hofuf Formationconsists of three distinct

facies: clast-supportedconglomerate, coarse-grained sandstone, andfine-grained sandstone.


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Dam Formation

• In Qatar the Dam Formation has been dividedinto Lower and Upper Damsub-formations.

• The Lower Dam consists ofaround 30 m of white andlight gray fossiliferouslimestone, marls and clays,which are of marine origin.

• The Upper Dam is formed of

around 50 m of creamy andlight gray limestones withthe occasional evaporites,clay beds, marls andmicrobial laminations.


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Dammam Formation

• The Dammam

formation consists

mainly of limestone and

dolomite.• It is divided into a four

members.

• These are the Midra,

Dukhan, Umm Bab and

Abaruq


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The Dammam Formation


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Rus Formation•

In Qatar, only the upper part of theformation is exposed, where around25m of the formation are exposedat around 1 km from the QatarPetroleum plants at Fhahil inDukhan area.

• The formation is divided into two

members namely Al Khor andTraina.

• Al Khor Member consists of around25 m of fine-grained chalkylimestone alternation with marl andclay at top.

• The Lower part of the Trainamember consists of alternations ofmarls and dolomitic limestone,while the upper part is formed ofcoarse limestone with mud balls.

Rus

Dammam


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Water Resources

• All fresh water in Qatar is

coming from desalination

plants and groundwater.

•

The groundwater systemof Qatar is that of Eastern

Arabia and aquifers are

found mainly in the

Tertiary strata.• Most of the groundwater

are found in three

aquifers.


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Umm er Radhuma Aquifer (Paleocene)

• The Umm er RadhumaFormation consists of 300-500m of alternatinglimestones and dolomites.

•

The top 30-50m ischaracterized by thepresence of karsticdolomite.

• The marl content of the

formation increasesdownwards. This aquifercontains brackish waterbeneath the wholecountry.


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The Rus Aquifer• The Rus aquifer is formed of

tight evaporitic zone ranging inthickness between 10-100m ofanhydrite with marl and somethin limestones.

• This zone is overlain and

underlain by a succession ofaround 10-20m composed oflimestone, dolomite and somemarl.

• The anhydrite facies representsan aquiclude, while the

carbonate facies is importantaquifer containing large reservesof freshwater, and is in hydrauliccontinuity with Umm erRadhuma formation below.


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Dammam Aquifer

•

The lower Dammam Formation consistsof about 12m of compact, fossiliferous,chalky limestone with laminatedfossiliferous shale.

• This shale unit has confined the Rusgroundwater.

• The absence of shale from northernQatar has great recharge significance andrepresents a controlling factor in thesolution of gypsum from the underlyingRus Formation.

• The Upper Dammam ranges in thicknessbetween 10-65m and composed of

dolomitic limestone, it is an importantartesian aquifer in southwestern Qataronly, but unimportant elsewhere.

• The Dammam aquifer is connected tothe Umm er Radhuma aquifer, andcontains old water (10,000 to 17,000

years).


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Water provinces

• There are three distinctive hydrogeologic

provinces in the country. This subdivision is

based on changes in the hydrogeologicalcharacteristics of the Rus Formation in terms

of the presence of carbonates, sulfates and

residual facies zones.


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Northern Province

• In the northern part of the country, freshgroundwater is found mainly in the Rus and upperUmm er Radhuma formations.

• In this province, the carbonates and residual

sulfates are in direct contact with the seawaterthrough the permeable Umm Bab limestone anddolomite and without the immediate isolationprovided by the lower Dammam shales and clays.

• Therefore, the groundwater is under the effect oflateral salt intrusion and the fresh water floats aslenses on brackish and salt water.


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Southern Province

• This province covers more than half the total areaof the country and characterized by the presenceof evaporite sediments.

• Such sediments are formed of gypsum overlainby a thin layer of dolomitic limestone of theupper aquifer unit (Dammam) and underlain bythe thick carbonate of the lower aquifer unit(Rus).

• In this zone, there is an aquitard of evaporite unitof the Rus Formation except where theoccasional collapse depression allowed watermovement between the lower and upper units.


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Southwestern Province

• This province is characterized by the presence

of artesian aquifer within the Upper

Dammam.

• The aquifer consists of dolomitic limestone

interbedded with marls


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Thank You

Documents

Geology of Qatar 2015