Table 1. Typical densities for Bay area rocks

Age is in millions of years; densities are in grams/cubic centimeters, M is magnetic

Rock type	Age	Range	Average
	millions of years	grams/cubic centimeter	grams/cubic centimeter

Quaternary sediments (Qs)

Cenozoic volcanic rocks^M
(Czv)
Tertiary sedimentary rocks
(Ts)
Cretaceous sedimentary rocks
(Ks)
Cretaceous and Jurassic
Franciscan Complex (KJf)
Mesozoic igneous rocks (Mzi)
(includes gabbro^M)
Mesozoic metamorphic rocks (Mzm)
Mesozoic granitic rocks (Mzg)
Mesozoic serpentinite
(Mzsp)

0-2

0-65

2-65

65-140

65-210

65-250

65-250
65-250
65-250

1.7-2.2

2.2-2.7

2.2-2.6

2.6-2.7

2.6-2.8

2.7-3.0

2.6-2.8
2.6-2.8
2.2-2.8

2.0

2.5

2.4

2.65

2.67

2.8

2.7
2.67
2.4