EBS101 ENGINEERING GEOLOGY DR HAREYANI ZABIDI GEOLOGICAL MAPS EBS101 ENGINEERING GEOLOGY DR HAREYANI ZABIDI

OBJECTIVES To read and interpret geologic maps To learn the rule of V’s and understand the relationships between contacts and contour lines To locate and identify the 3 major fault types on maps and cross sections To recognize unconformities and intrusions on maps To interpret geologic history from a geologic map

Frequently-used maps Solid and Drift map – shows the distribution of the various rocks and soils that occur close to the surface of the ground Useful for civil engineering work Subsurface maps – show the thickness and underground distribution of rock and soil Useful for mining engineers and others whose engineering work is located at depth

Solid and drift maps Drift edition – a map of surface geology, shows the position, and the general character of all geological materials that occur at ground level Harder rocks and all other materials, such as alluvium, glacial drift, mud flows, sand dunes, etc. All these have been transported or drifted, to their original position; called a drift edition

Solid and drift maps Solid editions – not all drift at ground level is thick, much can be thin Often to construct a map beneath the drift; when no drift is shown on a map, only the solid geology; called a solid edition Thus the geology of an area can be studied using two maps, Showing the drift and the solid geology; between areas of drift Showing only the solid geology beneath the drift areas

What is a geological map ? Gives information on the superficial layers of the earth’s crust The geological information are listed according to their composition (lithology), their age (stratigraphy) and their structural position (tectonic) Placed on a topographic base (map) using different graphic elements (symbols, figurative and color) The choice of scale depends on the geological content and the intended objective of the map.

A geologic map is an illustration of a huge volume of geologic information. Using a geological map, a geologist can show the distribution of rock bodies at the surface of the Earth and geologic structures which have deformed those rocks. Geological maps show the occurrence, nature, extent and stratigraphic age of rock strata in a district

How are geological maps made ? The essential condition for establishing a geological detail map is a precise field survey, based on numerous measurements and observations. The topographic base is generally taken from maps at a scale of 1:10'000, such as those of the comprehensive cadastral plans.

The field geologist determines the rock type according to various criteria and measures its orientation. All data are transcribed onto the map and in a field notebook. Besides the natural or artificial outcrops, data from bore holes or important test holes are taken in consideration.

In the case of a doubtful rock identification, complementary investigations are carried out in the laboratory on samples of these rocks. At the end of the field survey, the geologist establishes an original draft at a scale of 1:25'000 and constructs some geological sections across the studied sector. He also writes an explanatory note that generally contains numerous illustrations.

The geological cartography section assures the direction of the project, carries out the editing of the map, establishes the final legend of the map and provides indispensable data for the cartographers.

GEOLOGICAL MAP OF KUALA LUMPUR (GOBBETT, 1964)

Modern karst Aureole zone Paleokarst Quartzite and phyllite ----- ANGULAR UNCONFORMITY ----- Calcitic marble Fine grained - black graphitic schist Fine grained - quartz- mica schist Graf/ diagram to prove the chemical observation Series of vertical faulting – cut both granite and sediment formations Younger than quartz veins

Structure and Cross Section Sheet 94 Kuala Lumpur SELANGOR 4 cross section: 1 cross section – aligned with SMART project 3 cross sections – cross the alignment of SMART project Details of solid geology and structural geology Potential of karst formation Graf/ diagram to prove the chemical observation Schematic diagram showing direction of cross sections in Kuala Lumpur

Cross Section 1 Aligned with SMART project location Geological profile parallel with SMART project Development of karst: Unconformity boundary – Kuala Lumpur Limestone Formation and Kenny Hill Formation Contact zone – Kuala Lumpur Limestone Formation and granitic rock Graf/ diagram to prove the chemical observation

Cross Section 2 Northern part of SMART project Opposite direction of SMART project Development of karst: Contact zone – Kuala Lumpur Limestone Formation and granitic rock Fold – Hawthornden Formation

Cross Section 3 Crossed SMART project alignment Crossing folded Kuala Lumpur Limestone Formation Development of karst: Contact zone – Kenny Hill Formation – Granitic rock

Cross Section 4 Southern part of SMART project Development of karst: Contact zone with Kenny Hill Formation Fault in Kuala Lumpur Limestone Formation Klang River

A GEOLOGICAL MAP, GEOLOGICAL CROSS-SECTION AND 3D STRUCTURE

MAP INTERPRETATION

OUTCROP PATTERNS Horizontal beds – outcrops follow the contours; constant altitude Vertical beds – straight outcrops ignore the contours (dyke on the Tan Vale map) Dipping beds – curved outcrops; cut across and respond to the contours (erosion) – sandstone Dip direction – V in Valley Rule; an outcrop of a dipping rocks bends around a V shape where it crosses a valley, and the V of the outcrop points in the direction of dip

5. Succession – younger rocks coming to outcrop in the direction of dip. 6. Width of outcrop – greater on thicker beds and at lower dips

STAGES OF MAP INTERPRETATION Identify faults and unconformities (structural breaks) Identify dips by V in Valley Rule Determine succession Identify fold axes (dip and outcrop bends) Draw stratum contours Draw cross-section to show sub-surface structure

Transformation from locality to a map

Tutorial 1