Mecca Hills’ Painted Canyon

Structural geology of deformed sedimentary and basement rocks

within the San Andreas Fault zone

GLG455/598

Advanced Field Geology

View southeast over the Mecca Hills

Mecca Hills

Painted Canyon

Tent camping on the beach: $7/night x 2 camps=$28/11 people ~ $3 each

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Logistics

• Depart Fwing loading dock at 4 pm on Friday.

• Return early evening on Sunday night

• Bring camping gear and field gear

• We will provide kitchen system

• Organize food groups (if desired) and purchase items before Friday

Forecast from weather.com

Nominal mapping area: transect 6.2 km long

Mapping exercise: Produce a geologic map along this transect which is mostly perpendicular to the major structures. -Many strike and dips of faults and bedding plotted on the map-Major stratigraphic contacts and basement contacts-Rock descriptions

Generalized stratigraphy in the Mecca Hills

Basement: Highly sheared gneiss and granite of the Chuckawalla complex; Orocopia Schist

Unconformity or fault along Box Canyon

Nice folds and faults in Painted Canyon

Sedimentary structures in Plio-Pleistocene units

Some basement rocks are involved in the deformation

Structural planes

• See handouts and a couple of movies

• See also Reynolds’ web sites:– http://geology.asu.edu/%7Esreynolds/blocks/0_

start_here.htm– http://geology.asu.edu/%7Esreynolds/apparent_

dip/apparent_dip_gallery.htm

Davis and Reynolds, 2000

Ragan and Arrowsmith, 2002

Ragan and Arrowsmith, 2002

Ragan and Arrowsmith, 2002

Strike and dip notation

• Azimuthal

• Quadrant

• Dip/dip direction

Measuring strike and dip

Ragan and Arrowsmith, 2002

Ragan and Arrowsmith, 2002

Davis and Reynolds, 2000

Davis and Reynolds, 2000

Davis and Reynolds, 2000

Ragan and Arrowsmith, 2002

Davis and Reynolds, 2000

Basic steps in the preparation of a geologic cross section:

1) Choose appropriate line of section

2) Produce topographic profile along it.

3) Transfer marker attitudes (contacts and within units)

4) Correct for apparent dip in line of section (if line <75 degrees from strike)

5) Draw units; maintain stratigraphic thickness where possible; use deformation patterns observed from field to guide interpretation. Continue lines into air and below groundDavis and Reynolds, 2000

Davis and Reynolds, 2000 Ragan and Arrowsmith, 2002

Davis and Reynolds, 2000