[Rockhounds] salmon creek WA

[RicSchager at aol.com]

If really coprolite (feces), under what circumstances would they  be remain 
in such perfect shape and form as they became siderite concretions,  but at the 
very same time no fossil bones, turtle shells, fish, etc. are  found 
associated with these? 
 
Rich.
 
In a message dated 4/4/2008 3:56:32 A.M. Pacific Daylight Time,  
teyancey at suddenlink.net writes:
 
It has  been enjoyable to watch this exchange of messages, because it 
is a  confirmation of Pete Modreski's comment that when a locality 
name is  mentioned in a message without any indication of state or 
region, it can  be assumed to be refering to a place in the Pacific 
Northwest states of  the U.S. In this case, 10 days passed before the 
state was  identified.

In many ways this is a very interesting locality. It is the  source of 
most of the coprolite concretions that are sold in the rock and  
mineral trade in North America. Large numbers of coprolites have been  
collected in the area for years. While these are generally well  
accepted as coprolites, among residents in the Pacific Northwest 
there  has long been controversy about their origin. Many people in 
the region do  not believe in a coprolite origin for them and 
publications on geology of  the area usually debate this issue. Very 
similar coprolite concretions  from other regions (Canada, Madagascar) 
are accepted as coprolites, but  the origin of the Salmon Creek 
concretions remains  contentious.

These concretions are formed of the mineral siderite and  they do not 
retain any fabric of the original feces, although the external  
morphology can be preserved in excellent detail. Many of them are now  
oxidized to iron oxides and the process of mineral change can create  
so much alteration in appearance that their origin cannot be  
determined, contributing to confusion. Also, many that are found in  
the stream bed of Salmon Creek or in older stream gravels have been  
rounded by transport. The sediments of the streambanks also contain  
many concretions of all sizes and it is possible to find virtually a  
continuum between large, irregular iron oxide concretions and well  
formed siderite coprolites. The sediments contain large amounts of  
carbonized wood and the co-occurrence of carbonized wood and siderite  
appears to be characteristic.

Another feature of the site is that  it is located a short distance 
northwest of Mt. St. Helens and the  sediments exposed along Salmon 
Creek contain a lot of volcanic material,  including a couple ash 
layers. Late Miocene in age.

Some brief  answers to Gary's questions:
- The feces were dropped into soft mud on a  pond bottom and quickly 
replaced with siderite.
- There were a lot of  animals at the site.
- Turtles.

Tom  Yancey






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