Folds I

Advanced Tectonics
James S. Aber

Tectonic Folds in Sedimentary Strata

Landsat TM image of the Zagros Mountains, Iran. The mountain ridges are anticlines that have been partly eroded. Dark spots are salt diapirs that have extruded at the surface. Image acquired from the NASA Goddard Space Flight Center--GSFC.
Mt. Kidd, Kananaskis Mountains, Alberta, Canada. Thick Mesozoic carbontate strata are tightly folded in the Canadian Rockies front range.
Mt. Kidd, Kananaskis Mountains, Alberta, Canada. Closeup view of folds created by "thin-skinned" thrusting over a décollement in underlying rocks.
Mt. Tyrwhitt, Kananaskis Mountains, Alberta, Canada. Another example of tight, chevron-style folds that are relatively shallow structures.
Landsat TM image of Harrisburg, Pennsylvania. Image date 11/82; composed of TM bands 2, 3, and 4. Image acquired from the NASA Goddard Space Flight Center--GSFC.
Sideling Hill, a large syncline in Lower Mississippian strata of the Appalachian Valley and Ridge province. Notice the trough of the syncline is the crest of the hill. Exposure along I-64 in western Maryland.
Complex folding of incompetent strata in the Ouachita Mountains. Big Fork Chert (Paleozoic), Hot Springs, Arkansas.
Closup view of convoluted folding in the Big Fork Chert, Hot Springs, Arkansas.
Large overturned folds of Mesozoic carbonate strata in the Helvetic Alps. Anticline to left; syncline to right. Field of view is about 1 km across. Lütschental, central Switzerland.
Overturned syncline portion of large fold structure at Lütschental, central Switzerland.
Closeup view of syncline at Lütschental, central Switzerland. Notice the distinctive kink bands on either side of the main fold.
Overturned anticline portion of the folded structure at Lütschental, central Switzerland.
Closeup view of the anticline axis (scene center), Lütschental, central Switzerland.
Highly fractured and vein-filled rocks are typical of folded mountain systems. Pebbles derived from Devonian strata, Wembury Bay, near Plymouth, southwestern England.

Non-Tectonic Folds in Sedimentary Strata

Thick carbonate strata of the tectonically stable Ozark region. Mississippian Limestone, Roaring River State Park, Missouri.
Ground-water solution and cave development lead to collapse of surficial strata. Anticline structure in Mississippian limestone, Ozark region, Missouri.
Isoclinal fold in sand, clay, and till. Glaciotectonic (ice-push) deformation created this recumbent fold in drift. Half km west of Hvideklint, island of Møn, Denmark.
Core of isoclinal fold. Pen marks the horizontal fold axis. Half km west of Hvideklint, island of Møn, Denmark.
Small, recumbent, nearly isoclinal fold in "dislocated" till, Vagtbo section, island of Møn, Denmark. The fold is offset by small normal faults.
Small diapirs of clayey silt (dark) within sand, glaciomarine sediment, island of Herdla, near Bergen, Norway. Glacial loading caused the soft, water-saturated clayey silt to intrude upward into sand.

Folds--part II.
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Notice: Advanced tectonics is presented for the use and benefit of students enrolled at Emporia State University. Others are welcome to view the course webpages. Any other use of text, imagery or curriculum materials is prohibited without permission of the instructor. All text and images © J.S. Aber (2014).