Criteria for Faulting 4. Silicification and Mineralization Faults, because they are extensive fractures or branches of large fractures, are often the avenues for moving solutions. The solutions may replace the country rock with fine-grained quartz, causing silicification. This phenomenon in itself is not proof of faulting, but in some localities it may be highly suggestive. Mineralization along faults is typical of many mining districts.

Criteria for Faulting 5. Differences in sedimentary facies Different sedimentary facies of rocks of the same age may be brought into juxtaposition by large horizontal displacements. The figure illustrate very diagrammatically a basin of deposition in which sandstones are deposited near shore, shales farther out, and limestones farthest from shore. The transition from sandstone to shale, and from shale to limestone, will be gradual and there will be considerable interfingering of beds. The rocks of this particular age are said to be represented by sandstone facies in region A, a sandstone facies in region B, a shale facies in region C, shale-limestone facies in region D, and a limestone facies in region E. A large overthrust or a strike slip fault may bring the sandstone facies of region A into contact with limestone facies of region D. Sandstone Shale Limestone A B C D E

Criteria for Faulting 5. Differences in sedimentary facies

Criteria for Faulting 6. Physiographic criteria Physiographic features are the most effective criteria for recognizing faults. The following physiographic features can be used as evidence of faulting:- a. Offset ridge b. Fault scarp c. Piedmont scarp d. Offset stream e. Spring f. Topographic inversion

Criteria for Faulting 6. Physiographic criteria a. Offset ridge: Resistant sedimentary formations are generally expressed topographically by ridges. A dip-slip fault or diagonal fault will displace the strata, and consequently, the ridge held up by some resistant bed will be discontinuous, and an offset ridge will result.

Criteria for Faulting 6. Physiographic criteria b. Fault scarp: A scarp is a relatively steep, straight slope that may range in height from a few feet to thousands of feet. A scarp is not, of course, proof of the presence of fault, because scarps may originate in other ways, erosion by wave action. But a scarp that truncates topographic features, such as alternating ridges and valleys is highly suggestive of a fault.

Criteria for Faulting 6. Physiographic criteria b. Fault scarp: A scarp is a relatively steep, straight slope that may range in height from a few feet to thousands of feet. A scarp is not, of course, proof of the presence of fault, because scarps may originate in other ways, erosion by wave action. But a scarp that truncates topographic features, such as alternating ridges and valleys is highly suggestive of a fault.

Criteria for Faulting 6. Physiographic criteria b. Fault scarp: A scarp is a relatively steep, straight slope that may range in height from a few feet to thousands of feet. A scarp is not, of course, proof of the presence of fault, because scarps may originate in other ways, erosion by wave action. But a scarp that truncates topographic features, such as alternating ridges and valleys is highly suggestive of a fault.

Criteria for Faulting 6. Physiographic criteria b. Fault scarp:

Criteria for Faulting 6. Physiographic criteria c. Piedmont scarps: Sometimes called scarplets, lie at or near the foot of mountain ranges. They are confined to areas of active faulting. The height is generally measured in feet or tens of feet. They are generally straight and uneroded or only slightly eroded; that is, the face of the scarp is also a fault plane. Some cut the bedrock, but others are confined to the overlying unconsolidated deposits such as alluvial fans, glacial moraines and lake terraces.

Criteria for Faulting 6. Physiographic criteria d. Offset stream: Offset streams are found along active strike-slip faults. If a easterly flowing stream is offset by displacement along a north-south trending steep strike-slip fault, along which the east wall moved relatively south, the stream on the west wall will be offset relatively toward the north.

Criteria for Faulting 6. Physiographic criteria d. Offset stream:

Criteria for Faulting 6. Physiographic criteria e. Spring: Springs aligned along the foot of a mountain range are highly suggestive of faulting, especially if the water is hot. The alignment suggests the presence of a major plane of weakness, and the hot water indicates a fracture that permits deep penetration of circulating waters.

Criteria for Faulting 6. Physiographic criteria f. Topographic inversion: Inverted topography or topographic inversion refers to landscape features that have reversed their elevation relative to other features. In other words, topographic inversion is one in which the expected elevation of terrain is found lower or higher than the adjacent landmass. The axial region of an anticline have higher topographic elevation and the synclinal trough have lower topography. But, this can be inverse due to faulting or differential erosion.