ARNOLD — THE PALEONTOLOGY AND STRATIGRAPHY OF SAN PEDRO. 



21 



Dr. Lawsoii in discussing the movements that have taken place during late 

 Tertiary and Pleistocene times in the vicinity of San Pedro, says :' "It follows that, 

 while there is a very profound physical hreak between the Miocene and Pliocene, 

 the marine Pliocene and Pleistocene formations are intimately associated, with no 

 epoch of subai'rial denudation hetween them." The observations (jf the writer also 

 show this to be true, although in some places there is evidence of local denudation 

 between the Pliocene and Pleistocene. At Deadman Island, in particular, there is 

 evidence of a period of denudation between the two. 



Beds of a fine gray sand, with gentle north dip, rest uj^on the Pliocene ex- 

 posed along the railroad grade leading up to the cut in the bluff in the southeastern 

 portion of San Pedro. (See diagram D, PI. XXII.) The exact relation between 

 these gray sands and the underlying Pliocene is uncertain, as detritus covers the con- 

 tact along the face of the bluff. But the gray sand beds seem to rest almost conform- 

 ably on the yellow Pliocene deposits, both having a low dip toward the north. One 

 of the layers of gray sand near the top of the bluff north of the railroad grade con- 

 tains a fauna similar to that of the lower San Pedro stratum of Deadman Island. 

 This stratum is exposed in the bluff to the north of the San Pedro valley, and also in 

 two small cuts in the bluff west of the business portion of the town. These gray 

 sand strata were continuous at one time, the San Pedro valley, which cuts them, 

 having been formed by recent erosion. 



In the bluff to the north of the valley the fossiliferous lower San Pedro stratum 

 is about forty feet above tide level and dips northward, disappearing under detritus 

 at the mouth of a small ravine about three hundred yards from the southern end of 

 the bluff, but appearing again north of the ravine at the base of the bluff. Under- 

 lying this lower San Pedro bed are gray sandy strata which correspond to the lower 

 part of this same formation south of the valley, and which are unfossiliferous, except 

 in a few places. The following fossils have been found in the lower San Pedro beds 

 in the San Pedro bluffs. 



List of Fossils of the Lower San Pedro Beds at the San Pedro Bluffs. 



Anguluii huttoni 

 Anomia lampe 

 Cardium corhin 

 f'orhula luU'ola 

 ('rijiiloinya calij'ornica. 

 Cumingkt cati/oniicu 

 Donax californira 

 Donax lavigata 

 Hinnitea giganlcus 

 Kellia laperousH 

 Kellia Kuborbkular'iK 

 Ltevicariliiim subslriatum 

 Lazaria subyuadraia 



PELECYPODA. 



Leda var. prcecursor 

 Leda taphria 

 Lttcina acittitineata 

 Lucina cali/ornica 

 Lucina nultalli 

 Lyonsia California 

 Macoma nasuta 

 Macoma secla 

 Macoma yoldiformix 

 Mactra falcaia 

 Mylilimcria nutlalU 

 Nucula castrensis 



J^^ucula suprantriata 

 Oslrea lurida 

 Pecten latiauriltis 

 Pt'clen var. monolimerix 

 Psephis salmonea 

 Psephis tantilla 

 Semele decisa 

 Sitiqua lucida 

 Solen rosaceus 

 flolen sicarius 

 Tapes slaminea 

 Tellina bodegensis 



' Poat-Pliooene Diaatropblam of the Coast of Soutbera California. By A. C. Lawaon. Bull. Dept. Geol., Univ. of CaUfornia 

 Vol. 1, 1893, p. 128. 



