GEOS102 Labs PT2

Dip-slip

motion on the fault has moved parallel to the dip direction

Normal dip slip

Motion is parallel to dip and hanging wall moves down-dip

Reverse dip slip

Motion is parallel to dip and hanging wall moves up dip

Strike slip

Motion is parallel to the strike direction

Dextral strike slip

Motion is parallel to strike and direction is to the right of an observor

Sinistral strike slip

Motion is parallel to strike and direction is to the left of an observor

Oblique fault

Any combination of strike slip and dip slip occur

Axial plane

Plane or surface that divides the fold as symetrically as possible

Hinge line

Straight or curved line which joins the points of maximum curvature along the surface of a fold

Upright folds

Folds with vertical axial planes

Inclined folds

Folds with non-vertical axial planes

Plunging folds

Fold has hinge line which is not horizontal

Anticlines

Have oldest rock in sequence at the centre, beds dipping away from the hinge

Synclines

Youngest rocks in centre, beds dip in towards the hinge

Drawing map patterns (Strata cross section)

1. Draw on orientation of fault

2. Draw on strata on downthrown side of the fault, add relative ages of strata

3. Draw on strata on the eroded upthrown side of the fault and include relative age of strata

True stratigraphic thickness

Shortest distance between the upper and lower contacts of a bedding plane

Drawing map + cross section thickness

Start with map view, draw a straight line to be cross section line. Plot strike and dips, and then draw cross section view below.

Drawing thickness with different dips

Construct perpendicular lines to each bedding dip, the intersection of these lines is fold centre

Rule of V’s

In most cases, a dipping layer crossing a stream valley will V downstream in direction of its dip

V - Bedding dips downstream

Contact V’s downstream

V - Bedding is vertical

Contact is straight, cutting across topography (doesn’t V)

V - Bedding is horizontal

Contact follows topography (doesn’t V)

V - Bedding dips upstream

Contact V’s upstream

Bedding dips downstream BUT less than angle of the stream

V’s upstream

Relationship between dip and topography for V-ing

The steeper the dip, the LESS topography has an impact on degree of V-ing, the shallower the dip, the MORE topography has an impact on degree of V-ing