 | (Map site 1.) Roadcut exposing sandstone beds in the Upper Cretaceous Tuna Canyon Formation that was deposited in a shallow-marine fan delta environment.
 | (Map site 2.) Closeup of a thick conglomerate bed in the Upper Cretaceous Tuna Canyon Formation that was deposited in a shallow-marine fan delta environment. Note the roundness of the pebbles and cobbles which denotes a relatively long distance of transport before deposition.
 | (Map site 3.) Conglomerate deposits of the Upper Cretaceous Tuna Canyon Formation in the bottom half of the photo (about 80 million years old) overlain by basal sandstone layers of the upper Miocene Monterey Formation in the top half of the photo (about 10 million years old). The boundary between the two is called an unconformity. During the 70 million years of time missing between the two rock units several other rock units were deposited on top of the Tuna Canyon Formation, the area was uplifted, and all those rock units were eroded away before the area was once again submerged and covered by deposits of the Monterey Formation.
 | (Map site 4.) Roadcut showing many thin to medium sandstone layers in the upper Miocene Monterey Formation. Note that each layer of sandstone maintains a constant thickness.
 | (Map site 5.) Closeup of one of the sandstone layers shown in the previous photo. The depositional base of the layer starts by the "H" in Happy Birthday on the pen. The bottom half of the layer is parallel-laminated sand. Higher up where the layer starts to get a little yellow in color, several lens-shaped ripples are present. The darker colored top of the sandstone bed, under the overhang, is mostly silt and clay. A bed such as this is deposited by a submarine turbidity current on the slope of a submarine fan.
 | (Map site 6.) Roadcut exposure of shale layers in the upper Miocene Monterey Formation.
 | (Map site 7.) Closeup of the shale layers seen in the previous photo. As at Map Site 5, these shale beds also start with parallel lamination on the bottom and progress upward into ripple layering, which signifies deposition by a turbidity current on the middle slopes of a submarine fan.
 | (Map site 8.) These thick sandstone layers are part of the middle Miocene Upper Topanga Formation.
 | (Map site 9.) The two dark layers shown here are basaltic dikes that were intruded into cracks in the lower Miocene Lower Topanga Formation. At the time of intrusion, molten basalt made its way up through the cracks and eventually was erupted on the Earth's surface to form the lava flows that make up the Conejo Volcanics. The basalt that occupies the cracks here cooled before it got to the surface.
 | (Map site 10.) Closeup of a fossil turret shell called a Turritella which is imbedded in a sandstone layer in the lower Miocene Lower Topanga Formation. This fossil indicates that the sandstone was deposited in a shallow ocean environment.
 | (Map site 11.) The sandstone shown here is in the lower Miocene Lower Topanga Formation. Note that one set of layers has been truncated by erosion and overlain by another set of layers at a slightly different angle. This is referred to as cross bedding and it indicates that the river or ocean bottom had a wavy or dune-shaped surface during deposition.
 | (Map site 12.) This basaltic dike rock was cracked into a rectangular pattern during deformation and uplift of the Santa Monica Mountains. Water moving along these cracks weathers and decomposes the rock, eventually turning it into sand. Weathering proceeds from the rectangular cracks in toward the center of each block, but at the places where the cracks intersect, water is more available and weathering proceeds at a faster rate, ultimately producing the circular weathering pattern seen here. (Continued in photo 13.)
 | (Map site 13.) The process described above in photo 12, when viewed in three dimensions, produces the spherical weathering pattern shown here. This is called spheroidal weathering. Note how the spheroidally weathered layers peel off when exposed on the surface like the layers of an onion.
 | (Map site 14.) View looking southeast at the Redrock fault (yellow line). Note that the resistant sandstone layers of the Lower Topanga Formation in the foreground have been cutoff and moved to the left where they appear in the middle upper part of the photo.
 | (Map site 15.) Sandstone beds in the lower Miocene Lower Topanga Formation are the most resistant rocks in the Santa Monica Mountains, commonly sticking out on the surface as unvegetated hogback ridges. The brushy areas between the ridges are commonly made up of softer shale layers.
 | (Map site 16.) The thin layers of pebbles and cobbles seen here in the Lower Topanga Formation are likely the result of deposition in river channels. Although most of the Lower Topanga Formation is marine in origin, parts of it in this area were deposited on a river floodplain.
 | (Map site 17.) A little below the floodplain deposits shown in photo 16 and in slightly older rocks, these oyster fossils indicate that at an earlier time the lower Miocene Lower Topanga Formation had been depositing in a very shallow ocean environment.
 | (Map site 18.) The poorly exposed rocks in the bottom half of this photo belong to the river floodplain deposits of the Sespe Formation. The resistant sandstone layers covering them are the basal sandstone layers of the Lower Topanga Formation which contain very shallow ocean water barnacle fossils. The transition between the two rock units marks a submergence of the land and a transgression of the ocean shoreline across it.
 | (Map site 19.) Roadcut exposure of the Conejo Volcanics, which have been dated as being 17 million years old. When molten lava is erupted under water in the ocean, the front of the lava flow cools and cracks on contact with the cold water. More molten lava squirts out of the cracks in the flow forming blobs or pillow-shaped masses of cooled lava. These lava pillows crack and break and fall to the bottom of the ocean and eventually are incorporated into the advancing lava flow. A lava flowed formed in that manner is seen here.
 | (Map site 20.) Closeup of the Conejo Volcanics pillow breccia described in photo 19.
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