Page 17 - flint1939

12.

thousand feet thick. In the tyne locality there is no fossil
record so the :'-~odelo has been dated by its strategraphic rela-

tions with forrr.ations cf kncwn age. It is a rr.ari~e formation
and is the only one in this region. Because of this fact the

finding of marine fossils definitely -:-laces an unznown outcr.::p
in the 11'.odelo. The occurrence in the area under study attains

a maYimum thickness of 200 feet in the south',vestern part of the
area and thins OLt gradually to the southwest, eventually dis-

appearin~entirely.
The basal member of the ~odelo is a well cememted, lava

bearing conglomerate member 1/llhich varies in thickness and
constitution as it extends northward. The maximum thickness

of this conglomerate member is about 25 feet in the cliff in
the western area. As the bed thins, it undergoes a change in

composition, becoming more sandy, less well lithified and very

like the Mint Canyon. Above this basal member are a series of

fine grained sandstones; scely, finely bedded shales; and coarse

sandstones which complete the thickness of the formation in

this area. These beds are truncated under the Saugus which
laps over the Modelo onto the Mint Canyon to the northeast.

The rock composition of the Modelo is almost identical
with that of the ~int Canyon and it is only by the use of

colcr changes and a few other criteria that they wa.y be dis-
tinguished. The Mint Canyon is a predominately white formation

and the lower members of the Modelo are brown thus giving a
means of differentiation. Higher in the Modelo section the