The Geology of the Coast lianges. — Lawson. 343 
port. The present note is intended as a brief abstract of that 
paper, which shares the usual delay attendant upon govern- 
ment reports. 
General Outline of Geology. 
The investigation of the geology of the San Francisco pen- 
insula has revealed the existence of many sedimentary and 
igneous formations. The grouping of these in accordance 
with well known geological principles reduces them to seven 
groups, which, by reason of the technical sense attaching to 
the word group, are here referred to as terranes. This term 
is used as a necessary expression for any formation or group 
of formations in connection with the areal distribution of the 
same. These seven terranes in the order of their geological 
age comprise : 
1. Criistdliiiie limfstone, age unknown. 
2. (rfunite. referred to as the Montara granite, intrusive in tlie crys- 
talline limestoni'. 
3. The FraiicUcan series, an assemblage of sedimentary and volcanic 
rocks of great thickness, with which are associated various basic intru- 
sives, notably peridotite serpentines. This series rests upon the eroded 
surface of the Montara granite. 
4. A formation of light colored, cavernous-weathering sandstone which 
is supposed, doubtfully, to be of IVjoii (Eocene) age. 
5. The Monterei/ series {Miocene), chiefly white, siliceous, bituminous 
shale, practically devoid of delrital matter. (Nos. 4 and 5 together re- 
pose indifferently upon the Montara granite and upon the worn surface 
of the Franciscan strata just to the south of Ijat. 37° 30 .) 
6. 'Th^ Merced series (Pliocene), a thick volume of sediments with one 
stratum of volcanic ash deposited after the erosion of the Miocene. 
7. The Terrace formations. Pleistocene and later. 
Of these seven terranes, the Montara granite, the Franeis- 
•can series and the Merced series are the dominant features of 
the geology of the peninsula north of the parallel of latitude 
mentioned. South of that line in the Santa Cruz mountains 
the Monterey series is largely developed. All seven terranes 
are important factors in the general geology of the Coast 
ranges. The consideration of the petrography and tectonic 
of these various terranes, both as a wliole and as regards their 
constituent sedimentary and igneous formations, opens out 
many interesting problems. These have to do chiefly with 
conditions of deposition, nietaraorphism, diastrophism and 
geomorphogeny. The Montara granite introduces us to the 
still unsolved problem of the development of batholitic mag- 
