DESCRIPTION OF THE TYPE LOCALITY 



The fossiliferous asphalt deposits for which the name Rancho La Brea Beds 

 has been used were so designated from their occurrence at Rancho La Brea. 

 on the western side of the city of Los Angeles. The exact situation of the 

 typical locality is as follows : SW 14, sec. 21, T. 1 S, R. 14 W, San Bernardino 

 Base and Meridian. At this place excellent exposures are seen within a radius 

 of a few hundred yards of a small lake near the old Hancock ranch house. 

 The best exposures are found in the banks bordering several extensive open 

 cuts made by Major Hancock many years ago in excavating asphalt for com- 

 mercial purposes. The lake or lagoon and several small ponds in the vicinity 

 occupy depressions formed in mining asphalt. The work clone by Major Han- 

 cock in exposing extensive areas of the brea beds, and thus making them easily 

 accessible for examination by geologists and palaeontologists, has been in a 

 large measure contributory to the advancement of our knowledge of this region, 

 as otherwise the fossil-bearing beds might easily have escaped notice. 



The Rancho La Brea Beds lie in a wide stretch of slightly rolling country 

 immediately to the south of the abrupt southern slope of the Santa Monica 

 Range. The t} r pical exposures are situated about two and one-half miles from 

 the southern base of the range, and are about two hundred feet below the level 

 from which the mountains rise abruptly. 



In the region immediately about the type locality asphalt is exposed in many 

 places, and is evidently only a short distance below the surface over an area 

 at least as large as that in which it actually outcrops. At many points in this 

 region tar springs or seeps pour out considerable quantities of bituminous 

 material. The flow from these seeps is fairly regular in some cases, but at 

 other points more or less irregular exudation occurs through small crater-like 

 vents. The phenomena of extravasation of bituminous products are seen to best 

 advantage in the immediate vicinity of the lagoon or lake, where tar springs 

 and tar seeps are readily discovered. In addition to the outflow of the heavier 

 substances, large quantities of gas may be observed coming up through the 

 water of the lake in great bubbles. 



Estimates of the probable extent of the territory in which asphalt beds lie 

 at or near the surface have been made by several persons familiar with this 

 region. The approximations range from about a square mile down to one- 

 fourth of a square mile. The probabilities seem in favor of making the estimate 

 too low rather than too high. 



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