File:Normal fault in laminated mudrock (Emigsville Member, Kinzers Formation, Lower Cambrian; north of Lancaster, Pennsylvania, USA).jpg

English: Faulted mudrock from the Cambrian of Pennsylvania, USA. (field of view ~3.5 centimeters across at its widest)

Horizontal stratification is the # 1 most common sedimentary structure. Layers that are over 1 centimeter thick are called "beds". Layers that are less than 1 centimeter thick are called "laminations". This is a nice, finely-laminated mudrock sample from the famous Kinzers Formation of Pennsylvania. Well-preserved laminations indicate lack of post-depositional disturbance by burrowing organisms. This could be due to a lack of food in the sediments, or a lack of sufficient oxygen in the environment, or other factors.

Note the small-scale fault that is offsetting the laminations. Faults are fractures or fracture systems in rocks along which there has been differential displacement. Normal faults form by extensional stress. Reverse faults and thrust faults form by compressional stress. The example seen here is a normal fault.

The Kinzers Formation is best known for having soft-bodied fossils and preserved non-mineralizing parts in organisms that otherwise do have mineralized shells or skeletons (see elsewhere in this photo album).

Stratigraphy: middle Bonnia-Olenellus Assemblage-zone, Emigsville Member, Kinzers Formation, middle Dyeran Stage, upper Lower Cambrian

Locality: locality "K-4a" of Ethan Skinner - float from the southern side of an east-west elongated hilltop (= "K-4" of Campbell, 1969, Stratigraphy and Paleontology of the Kinzers Formation, Southeastern Pennsylvania.) along Settlers Bend road (during its construction), old Haverstick Farm property, north of Blossom Hill, north of the town of Lancaster, north-central Lancaster County, southeastern Pennsylvania, USA