11/10/08t
Cambridge Argillite 9/8/08
Mystery Stone
El Matador Beach, Malibu, California 9/1/08
Fossiliferous Sandstone
El Matador Beach, Malibu, California
This is the definitive sedimentary rock. It is very old. It became famous last year when a local geologist found Ediacaran fossils in it in Hingham. Below is an abstract from a paper that was presented on it last March. "Laminated Cambridge Argillite of the Boston Bay Group (Ediacaran) low-grade metasediments can be found in outcrop at Hewitt's Cove, Hingham, Massachusetts. These laminated sediments are finely graded layers 2 to 8 cm thick that are commonly interpreted in the literature as fine-grained turbidites (Stow sequences). Rhythmically laminated facies also occur that do not support a sediment-gravity flow interpretation. These rhythmites raise the possibility of sedimentation influenced by agents such as tides, waves, or wind. The Cambridge Argillite appears to consist of a subtle, but definite, mosaic of laminite facies that record multiple depositional processes, and perhaps multiple water depths." Now doesn't that say a lot! Unfortunately we don't know much about this little guy. If I was a betting person, I would say that the fossil probably came from the Green River Shale of Wyoming. The rock color is wrong, but other than that, it looks like a Wyoming fish. Tim, thanks for a great fossil! This is another sample from Matador Beach. So why does this sample look like this? It's a real mystery! El Matador Beach is one of those little gems in California found along the Pacific Coast Highway. You pay your $2.00 at the parking lot, and walk down a steep trail to a small beach. The geomorphology is nothing like what we have on the east coast. Huge sections of sedimentary cliffs have fallen into the sea, and they are being weathered into odd shapes, and eventually grains of sand. We were walking along the cliff face looking for unusual rocks when my daughter found this incredible piece of sandstone containing what look like a series of overlapping rings. The question is are the rings biological or chemical? I don't know. El Matador Beach is one of those little gems in California found along the Pacific Coast Highway. You pay your $2.00 at the parking lot, and walk down a steep trail to a small beach. The geomorphology is nothing like what we have on the east coast. Huge sections of sedimentary cliffs have fallen into the sea, and they are being weathered into odd shapes, and eventually grains of sand. We were walking along the cliff face looking for unusual rocks when my wife found this incredible piece of sandstone containing numerous fragments of shells.
11/10/08t
Cambridge Argillite
This is the definitive sedimentary rock. It is very old. It became famous last year when a local geologist found Ediacaran fossils in it in Hingham. Below is an abstract from a paper that was presented on it last March. "Laminated Cambridge Argillite of the Boston Bay Group (Ediacaran) low-grade metasediments can be found in outcrop at Hewitt's Cove, Hingham, Massachusetts. These laminated sediments are finely graded layers 2 to 8 cm thick that are commonly interpreted in the literature as fine-grained turbidites (Stow sequences). Rhythmically laminated facies also occur that do not support a sediment-gravity flow interpretation. These rhythmites raise the possibility of sedimentation influenced by agents such as tides, waves, or wind. The Cambridge Argillite appears to consist of a subtle, but definite, mosaic of laminite facies that record multiple depositional processes, and perhaps multiple water depths." Now doesn't that say a lot!
Return to Home Page
|
