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Individual Field Work Project

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by

Chafik Azar

on 16 July 2014

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Transcript of Individual Field Work Project

Introduction
The study area is situated in Central Northern Lebanon in the Jbail district between the two villages of Lalqouq and Tannourine el Faouqa.

Purpose:
Refine the geologic map of Dubertret
Fortify acquired methodologies, approaches and theoretical studies.
Enhance observation skills and critical thinking abilities.

Traverses
Stratigraphy
10 stratigraphic units were present

Jurassic strata:
Keserouane formation
Jurassic volcanics
Bhannes formation
Bikfaya formation
Structures
The study area revealed two types of geological settings; 4 faults and 1 fold (other than the Laqlouq fold).
Bedding planes & Joints
The beddings of all formations were measured and averaged to find that they all dip E.
The strata next to the Laqlouq fold are sharply dipping E in a near vertical manner as the dip becomes gentler as we move E.
All bedded formations show joints in specific directions.
After plotting and analyzing the joints, main stress directions prevailed.
Natural Resources
Three dolomite rich facies:
Chouane Member
Afqa Member
Upper part of the Mdairej Formation
Industrial use of Dolostone:
Used as a road based material, as an aggregate of concrete and asphalt.
Used for acid neutralization in the chemical industry.
Source of MgO, ingredient in the production of glass and ceramics.
Host rock for Zn, Pb, Cu and other metals formed from hydrothermal solutions.
Oil and gas reservoir rock. Dolomitization process creates pore spaces that could contain migrating oil from other lithologies.
Interpretation of Geologic data
Deposition took place from the upper Triassic and continued throughout the Cenomanian.
The compression and folding events in the Late Paleogene and Late Miocene contributed to the creation of the three Lebanese main structures. Both Laqlouq folds formed affected by this NNW-SSE compression giving the study area a compressional theme.
While folding, the Keserouane limestone exceeded its elastic limit and thus creating a normal fold.
Since the beds now dip East, a change in the stress vectors created the plunging anticline owing to a N-S compression event.
Modifications
Individual Field Work Project
A presentation by
Chafik Azar

Study Area
Location:
Laqlouq - Tannourine El Faouqa
Area:
22.5 square km
Elevation:
1800m asl
Previous studies:
(1) Tectonic evolution of Central Northern Lebanon (2) Late Jurassic vulcanicity in the Kartaba - Tannourine region

Geomorphology
Late Paleozoic-Early Mesozoic
Late Paleogene
Late Miocene
Multiphase Rifting
Rifting imposed an extensional theme over the majority of the region.
Extensional features, normal faults.
Syrian arc deformation
Inversion of extensional features.
Mainly dextral and thrust faults instead of normal faults.
This deformation gave rise to the main Lebanese structures: Mount Lebanon, Bekaa and Anti-Lebanon.
Severe Folding Event
NNW-SSE severe folding affecting the entire area
Laqlouq Flexure
Laqlouq anticlne formed affected by the folding and compression events.
Hinge line trends NNE-SSW.
Core of the fold:
Jurassic (Keserouane).
Limbs of the fold:
Jurassic (volcanics, Bikfaya)
Cretaceous (Chouf, Abeih, Mdairej)

Eastern limb of the Flexure
Traverses types
3 types were effectuated:
E-W traverses
Zigzag of the eastern limb of the flexure
Across the flexure
E-W Traverses
9 E-W traverses
approximately 500m apart
Elevation decreases as we went west
Length: on average 4.6 km
Starting point:
Sannine Formation (usually)
End point:
Keserouane Formation
Zigzag Traverse
1 traverse on the eastern limb of the Laqlouq fold
Length: 1.8 km
Starting point:
Chouf Formation
End point:
Abeih Formation
Across the Fold
1 traverse perpendicular to the axial trace of the anticline.
Length: 5.0 km
Starting point:
Keserouane Formation
End point:
Hammana Formation
Cretaceous strata:
Chouf formation
Abeih formation
Mdairej formation
Aptian volcanics
Hammana formation
Sannine formation
Keserouane Formation
Oldest formation exposed
located W of the study area
Heavily jointed & Karstified lithology
Sharply dipping E
Approximate height: 200-250 m
Composed of two distinct members
The Chouane Dolomite member
Lowermost unit of the formation
Grey color, forms white, beige sands upon weathering
Composed of anhedral grains whose pores are filled with iron oxides, organic material and pyrite.
The Nahr Ibrahim Limestone member
Overlying the dolomite member.
Bluish-grey color, creamy white on a fresh cut.
Composed of wackestones and have tightly packed matrices with little calcite veins intrusions.
The unit is unfossiliferous and heavily jointed and karstified forming wholes 15-30 cm in diameter.
The Late Jurassic Volcanics
Overlying the Keserouane formation. In the field it is underlying it.
Located W and N of the study area and is exclusive to the study area .
Commonly mistaken with the Bhannes formation, however it is not associated with brown limestone.
Maximum thickness: 50m
Extremely weathered (basaltic red-purple soil).
Resulted from the eruption of the Kartaba vent (Al Nadi, 1966)
The Bhannes Formation
Located N of the study area ONLY under the Bikfaya cliff trending E-W.
Very thin outcrops (max 10m) usually topped with thin soil cover.
Distinguishable formation as it is composed of two members.
The Basaltic member
Purple basalt.
Weathered into angular fragments 6-8 cm in diameter.
Contains high abundance of spheroidal exfoliation surrounded by dark purple soil.
The Limestone Member
Found on top of the basalt.
thinly bedded, brown-yellow limestone.
Thickness: 2 m.
The Bikfaya Formation
extends in the W and N of the study area; In the W it trends NNE-SSW, sharply dips E and is discontinuous, In the N it trends E-W, slightly dips E and is continuous.
Average thickness in the area: 23 m
Slightly fossiliferous.
Pale grey cliff showing alternations of beige and grey units.
Grey Unit
Sightly dolomitized micritic limestone.
tightly packed, very well sorted matrix.
Bounding surfaces present some bioturbated interbeds.
Beige unit
Beige-light brown sandy limestone unit.
Shiny texture showing an extremely dense pattern of calcite veins.
The unit exhibits a higher percentage of recrystallized fossil shells and chert nodules.
The Chouf Sandstone Formation
Most abundantly situated W and N of the study area; in the W it is narrow and laterally extends and widens as we move N.
The sandstone in the study area can be divided into three categories.
Quartz arenite
Located in the lower parts of the formation.
Yields a yellow-light orange color.
Consists of fine-medium grains of sand extremely friable and merely cemented with an extremely high quartz component.
Shows cross beds and fan-like piles of weathered white sand at the bottom of the outcrops.
Intercalated beds of green marl which may have lensoidal shapes in some localities and occasional peat laminae <0.2 mm thick.
Ferrugenous Sandstone
Found in the middle and upper parts of the formation.
Reflects a red, hematitic color.
It sometimes forms patches or displays hematitic interbeds.
Forms as a result of precipitation of iron met with an upward oxygen flow in deltaic environments.
Calcareous Sandstone
Found mostly in the upper part of the formation as the lithology starts becoming sandy limestone.
Contains Fe component as well.
Color darkens upwards as a transition between C1 and C2a is delineated.
The Abeih Formation
Widely distributed in the study area.
Sharply dipping E in the W of the study area.
shows in a distinguished brown-light orange lithology.
Near contact with C1, large lithified cross beds show.
Outer surface shows well-developped calcite rhombs in dissoluted and porous lithology.
Consists of sparse biomicrite with a matrix of 50% bioclasts and 50% coarse sand and angular pebbles.
Thick hematite veins cutting through + calcite veins.
Ammonoid and gastropod fossils are extremely abundant and well preserved.
The Mdairej Formation
Extensively found in the study area.
Instead of cliffy appearance, it shows intensely karstified topography, laterally discontinuous and separated with vegetation cover.
The lower contact with C2a shows intercalation zones mostly in the W part of the formation's exposure and abundance of macrofossils.
The upper contact with Aptian volcanics is dolomitized due to hydrothermal dolomitization.
Consists of grey wackestones with tightly packed matrices and calcite intrusions.
Extremely high secondary porosity and arstic features such as karrens and lapiers.
Aptian Volcanics
Found in the Eastern part of the study area between C2b and C3 sequences.
Thickest and widest volcanic unit of the area.
Mistaken with the basaltic member of Hammana but there are thickness contradictions.
Mostly weathered dark soil used for agriculture.
Black-greenish color with vesicular texture and high leucite concentration.
The Hammana Formation
Found in the E of the study area.
Does not exceed 80 m in height.
Lower part covered with thick vegetation cover and falling blocks however upper part has a cliffy appearance and composed of marly limestone transitioning into dolomitic limestone constituting the lower member of the Sannine formation.
Upper part consists of weathered marls (green, red and white) termed as the Knisseh member.
A very distinctive dark brown carbonate member termed Banc de Zumoffen which helps identifying the upper part of the formation is absent in the study area.
The Sannine Formation
Found in the E of the study area.
Thinly bedded and constitutes most of the mountain chains in the W.
Average thickness: 150m.
Reflect a creamy white color and consists of two members.
The Afqa Dolostone Member
Lowermost member of the formation.
Shiny and rough outer texture consisting of sand size dolomite crystals in a lime mud matrix.
The intercrsytalline pores are filled with organic material and clays.
Some bioturbated interbeds and radiogenic chert nodules were spotted.
The Aaqoura Member
Overlying the dolostone member.
Consists of chalky, marly limestone forming a porous but impermeable unit (aquiclude).
Macrofossils such as gastropods are modeately found as well as dark laminae of organic matter.
Fault I
Found on the lower Eastern part of the study area.
Cuts through C3 and C4.
083/64 fault plane.
Normal fault with an red hematitic marl index bed on the footwall.
Displacement measured between lower boundaries of the green marl bed = 60m approximately.
Faults II and III
Found in the center of the study area and are 50 meters apart.
Cut through Bikfaya --> Mdairej formations.
Normal listric faults oppositely dpping.
230 fault dips north whereas the 270 fault dips south.
The measured displacement of the Bikfaya cliff is approximately 35m.
The two faults form a graben structure in between.
Fault IV
It is found in the W of the study area, on the eastern limb of the Laqlouq fold but it is not outcropping.
normal fault trending NNE-SSW.
The fault may have been caused by the folding event, where the Keserouane limestone exceeded its elastic limit causing it to fail.
Plunging Anticline
Found in the E of the study area within the C4 sequence.
Its hinge line trends E-W suggesting a change in the stress vectors.
The hinge line plunges 25-30 degrees and has an interlimb angle of about 130 degrees thus the fold is classified as a gently plunging anticline.
Depositional environments
Depositional environments of the formations are governed by eustatic level changes. 5 transgressions and 3 regressions accompanied by 2 major unconformities in the Jurassic strata.
Keserouane Formation:
Deep marine setting
Bhannes Formation:
slight regression
Bikfaya Formation:
Oscillating sea level
Chouf Formation:
Regression, deltaic/fluvial setting
Abeih formation:
Transgressive, shallow marine setting
Mdairej Formation:
Transgressive, deep marine setting
Hammana Formation:
Regressive, very shallow marine setting
Sannine Formation:
Transgressive, ramp setting
Interactive geologic map
Refined geologic map
Full transcript