Oleh : Amien WidodoHP : 08121780246 Email : amien@ce.its.ac.idPeta geologi dan geologi lapangan

Structures and Geologic MapsRock structures are determined on the ground by geologists observing rock outcropsOutcrops are places where bedrock is exposed at the surface

Geologic maps use standardized symbols and patterns to represent rock types and geologic structures, such as tilted beds, joints, faults and folds

Orientation of Geologic StructuresGeologic structures are most obvious in deformed sedimentary rocks

Tilted beds, joints, and faults are planar features whose orientation is described by their strike and dip

Strike is the compass direction of a line formed by the intersection of an inclined plane with a horizontal plane

Dip is the direction and angle from horizontal in which a plane is oriented

Measurement of Strike DirectionRight hand rule???When your thumb (on your right hand) is pointing in the direction of strike your fingers are pointing in the direction of dip!!

Measure of Dip AngleThe angle between the horizontal and the line or plane

Structural DataSymbols represent different structural dataSymbols are placed on the map:in the exact field orientationwhere the data is measured

Standard Structural Symboles

V RuleBeds dipping downstream V downstreamBeds dipping upstream V upstream

Vertical beds cut straight Vertical oriented beds cut in a straight line regardless of topography!!

Strike and Dip on a MapMap ViewCross-Section

Types of Geologic StructuresFolds are wavelike bends in layered rockRepresent rock strained in a ductile manner, usually under compression

The axial plane divides a fold into its two limbsThe surface trace of an axial plane is called the hinge line (or axis) of the fold

Anticlines are upward-arching folds, and synclines are downward-arching folds

Folding and Age of LayersAnticlines eroded horizontallyat the surface show oldest agesin the center line.

Synclines eroded horizontallyat the surface show youngest agesin the center line (bedding ages are symmetrically older going away from center)

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