78 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 
built up in connection with a shifting of the stream channel, or channels, it is probably 
composed of an irregular alternation of mud, sand, and gravel. The fault-trace, as 
already, described, passes thru the midst of the tide lands, following the axis of the 
depression which contains the bay. Continuous with the mud of the lower slope of the 
delta is a mud shoal following the western shore of the bay past Inverness. ‘This shoal 
and other parts of the tide lands were seen soon after the earthquake from the road 
which follows the west shore of the bay to Inverness, and a few photographs were made. 
Other photographs were made at various dates afterwards, and the tide lands were 
explored on foot on April 18, 1907. 
A large portion of the delta was thrown by the earthquake into gentle undulations, 
the difference in height between the swells and hollows being usually less than a foot. 
Mud exposed at low tide | 
Tidal marsh 
oO [2 

Fic. 24. — Map of Papermill Delta at head of Tomales Bay. 
The chief evidence of this is found in the distribution of pools at low tide, and where 
vegetation is present the evidence from pools is supplemented by that from the condition 
of the plants. The undulations were not elongate and were not found to have a sys- 
tematic relation to the fault. 
When the tidal mud was first seen after the earthquake, it was observed to be covered 
with ridges and troughs. (Plate 548.) This corrugation was gradually smoothed out by 
the action of the waves (plates 558 and 56a), so that at the expiration of a year its expres- 
sion was largely lost, tho a few of the larger ridges could still be traced, and much of the 
plain retained a pattern imprest on it by the ridging. It is probable that the entire tract 
of tidal mud was thus affected, altho the ridges were not seen on the area lying nearest to 
the east shore. That area did not come under observation until after the spring floods 
