Geology 3120 Introduction to Thrust Faults Up Down

Geology 3120 Introduction to Thrust Faults Up Down 1

Outline • Terminology • Calculating stretch and shortening • Throw, heave, and slip • Stratigraphy and thrust faults 2

Thrust Fault 3

Thrust Fault Terminology Original layer cake template 4

Thrust Fault Terminology Foreland Hinterland Transport Direction Fault achieves trajectory rapidly 5

Fault Bend Fold Movie 6

Thrust Fault Terminology 7

Calculating Shortening for Thrust Faults lo lf 50 km 40 km lf - lo * 100% Shortening = lo If Stretch [S] = lf/lo, then shortening = ( l -1) lf o * 100% 8

Calculating Shortening for Thrust Faults lo lf 50 km 40 km Shortening = lf - l o lo * 100% = 40 - 50 * 100% = -20% 50 9

A Caution Regarding Shortening lo lf 50 km 40 km Choosing a minimum lo value yields maximum shortening Shortening = lf - l o lo * 100% = 40 - 50 * 100%= -20% 50 10

Shortening Calculation lo lf 40 km 30 km Shortening = n. Thus lf - l o lo * 100% = 30 - 40 * 100% = -25% 40 “shortening” is relative to the baseline you pick 11

Throw, Heave, and Slip Heave Throw Q Q Q Slip (Throw)2 + (Heave)2 = (Slip)2 Sin. Q = (Throw/Slip) Cos. Q = (Heave/Slip) 12

Increasing Stratigraphic Thickness 13

Evidence for Thrust Faulting in Boreholes 14

Evidence for Thrust Faulting in Boreholes 15

Evidence for Thrust Faulting in Boreholes 16

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References Slides 3 -9 http: //earth. leeds. ac. uk/faults/thrust/rampflat/index. htm Slides 10 -14 Twiss, R. J. and E. M. Moores, Structural Geology, W. H. Freeman & Co. , New York, 532 p. , 1992. 19