A chart of strata formation of Los Angeles County at the la Brea Tar Pits. At the top is recent geological formations, showing the Santa Monica Mountains. Reading down on the left hand side we then have Pleistocene and tertiary cross-sections showing geological structure with oil and asphalt seepage. Below that moving downward are the periods: recent alluvium (10000-25000 years ago) ; pleistocene-ice age (25,000-2,000,000 yrs) ; pliocene (2,000,000-20,000,000) ; miocene (20,000,000-35,000,000) ; oligocene (35,000,000-45,000,000) ; eocene (45,000,000-60,000,000) ; upper cretaceous (60,000,000-80,000.000 yrs. ago). Copied March 7, 1938.
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