STRATIGRAPHY OF THE PUGET GROUP. 5 
further transformation of the coal to anthracite and coke occurs in the vicinity of 
igneous rocks, to whose influence it is wholly due. 
The stratigraphic relations of the Puget series are not determinable within the 
area under discussion, since the strata nowhere come in contact with older sedi- 
mentary rocks. Sixty miles northward, on the Skagit river, is a contact between 
similar coal-bearing strata and older metamorphic schists, described in an earlier 
report * as possibly a surface of deposition or of faulting. Examination of this 
locality in 1895 led to the discovery of small pebbles of the schist forming a basal 
conglomerate in the sandstone beds next the contact, which was therefore a surface 
of deposition during a transgression. Fossils found in limestone under the schists 
are stems of crinoids of Carboniferous or Triassic age, whereas the coal-bearing 
sandstones of this locality are assigned by Knowlton to the Eocene on the evidence 
of numerous leaf impressions. 
The age of the Puget formation has been in doubt because of the obscurity of 
stratigraphic relations, the general absence of marine fauna, and the indeterminate 
character of the flora. Collections made for Newberry prior to 1884 represented 
various stratigraphic horizons which were not distinguished. Most of the species 
were new. Newberry correlated the plants with the Laramie (Cretaceous) flora, 
and the series has been dated late Cretaceous or early Eocene. A more definite 
correlation with the Tejon formation of California has been suggested by C. A. 
White. 
The latest evidence on this still debatable question is that of collections made in 
1895 and 1896 from definitely determined stratigraphic horizons on Green river, 
above Burnett on South Prairie creek, and on Carbon river near Carbonado. A 
preliminary examination of the fossil plants enables Knowlton to report that the 
lower beds of the series are Eocene, whereas the upper beds may be of Miocene 
age. The floras from horizons several thousand feet apart in stratigraphic range 
are so distinct as to afford means of correlating separate strata of the Puget forma- 
tion. Further collections and detailed studies must be made before we can deter- 
mine how closely coal beds may be identified by their fossil plants and to what 
extent the fossils will aid in working out the complex, obscure relations of distinct 
parts of the coal fields. 
Most prominent among the rocks associated with the Puget group are eruptives 
of Tertiary or later age. They occur as dikes and flows in various forms of in- 
truded and extruded igneous rocks. 
Thus the Puget series is related to four other groups of rocks, which may be 
named in order of their age, as follows: (1) Metamorphic schists and limestones of 
Carboniferous or Juratrias date, upon which the Eocene strata were deposited un- 
conformably, at least in the Skagit district ; (2) the marine Miocene, or Tejon, with 
which the Puget series is stratigraphically continuous; (3) the Tertiary eruptives, 
which are younger than the Puget group, and date down almost to the present 
time; (4) the Glacial gravel deposits of Pleistocene age. 
The measured sections of the Puget series exhibit total thicknesses of 5,800 feet 
on Green river, 5,500 feet on South Prairie creek, and 5,480 feet in Carbon River 
canyon. None of these measures is complete. In each instance the lowest stratum 
is of the Eocene outcropping on an anticline, and the highest is the limit of expos- 
ure where the rocks pass under later formations. These sections probably overlap, 
and there are also higher beds exposed on South Prairie creek above the limit of 
* Reports of Tenth Census, vol. xv, p. 760, 
