The Pliocene and Pleistocene History of the Baldwin Hills, Los Angeles County, California¹

Trenches near the Baldwin Hills (Inglewood Oil Field) exposed the best section of Pliocene-Pleistocene sediments known in the Los Angeles basin. A northeast-dipping series revealed (a) Upper Pliocene sands with a cold-water fauna; (b) hitherto unknown sands with a warm-water fauna; (c) “Lower San Pedro” sands with a cold-water fauna; (d) “Upper San Pedro” gravels and sands with a warm-water fauna; (e) freshwater sands and clays, carrying Mylodon, presumably the same species as is found at Rancho La Brea. Overlying all these beds was an unconformable bowlder bed of river origin. At this point a fault threw down beyond observation both the tilted series and the river bowlders. The bowlder bed may be very late Pleistocene. Overlying it, east of the fault, were peat-streaked sands—flood-plain or lagoonal deposits due to impounding. About halfway up in this material human remains were found. Their age is in doubt. Structurally, evidence exists that the Baldwin Hills is an uplift finally made in very late Pleistocene time, with a northwest-plunging nose.¹