Clastic dike


A clastic dike is a seam of sedimentary material that fills an open fracture in and cuts across sedimentary rock strata or layering in other rock types.
Clastic dikes form rapidly by fluidized injection or passively by water, wind, and gravity. Diagenesis may play a role in the formation of some dikes. Clastic dikes are commonly vertical or near-vertical. Centimeter-scale widths are common, but thicknesses range from millimetres to metres. Length is usually many times width.
Clastic dikes are found in sedimentary basin deposits worldwide. Formal geologic reports of clastic dikes began to emerge in the early 19th century.
Terms synonymous with clastic dike include: clastic intrusion, sandstone dike, fissure fill, soft-sediment deformation, fluid escape structure, seismite, injectite, liquefaction feature, neptunian dike, paleoseismic indicator, pseudo ice wedge cast, sedimentary insertion, sheeted clastic dike, synsedimentary filling, tension fracture, hydraulic injection dike, and tempestite.

Environments of formation

Clastic dike environments include:
  • Clastic dikes associated with earthquakes –
  • Clastic dikes associated with debris flows –
Image:Dikes in black dragon canyon UT.JPG|thumb|right|Red-colored clastic dikes injected downward into light-colored sediment beneath a debris flow. Black Dragon Wash, San Rafael Swell, Utah
Image:Upheaval dome clastic dike1 PWH.jpg|thumb|right|Clastic dike exposed on the east flank of the central peak of Upheaval Dome, Canyonlands, Utah. The sandstone dike was injected downsection from the White Rim Sandstone into the Organ Rock Shale during the earliest part of the impact crater excavation stage. The dike is made of cataclastically broken sand grains derived from the White Rim Sandstone. The slightly overturned Organ Rock beds dip steeply to the left and their tops face toward the right. The White Rim Sandstone, folded to vertical, lies just off the photo to the right. View is to the north. P.W. Huntoon Collection.
  • Clastic dikes associated with salt domes –
  • Clastic dikes associated with glaciers –
  • Clastic dikes in resistant bedrock –
  • Clastic dikes in storm deposits –

    Clastic dikes in the Columbia Basin

Tens of thousands of unusual clastic dikes penetrate sedimentary and bedrock units in the Columbia Basin of Washington, Oregon and Idaho. Their origin remains in question. The dikes may be related to loading by outburst floods. Other evidence suggests they are sediment-filled desiccation cracks. Some have suggested the dikes are ice wedge casts or features related to the melting of buried ice. Earthquake shaking and liquefaction are also suggested to explain the dikes.
The silt-, sand-, and gravel-filled dikes in the Columbia Basin are primarily sourced in the Touchet Formation and intrude downward into older geologic units, including:
In 1925, Olaf P. Jenkins described the clastic dikes of eastern Washington state as follows: