23 



area. In many coastal areas sediments become coarser with increasing 

 distance from shore and/or from river mouths because estuaries serve as 

 traps for fine sediments. Since depth, too, commonly increases with 

 distance from shore, a positive relationship between depth and coarse 

 sediments might usually be expected in coastal waters. Due to the 

 complex topography of the Casco Bay region, we cannot separate the 

 effects of depth, distance from shore, or even distance from river 

 mouths in regard to gross sediment parameters. We feel confident, 

 however, that all three factors are operative in controlling the grain 

 size distribution, hence the scatter around the regression line. 

 Because we cannot meaningfully quantify distance from shore or distance 

 from source, we use depth alone to represent a complex of related 

 factors. 



Fifty of the 55 stations have very poorly sorted sediments 

 (Table 2). With the exception of station 9, a coarse sand station which 

 is moderately well-sorted, the remaining stations are either poorly or 

 extremely poorly sorted. 



The percentage of sand, silt and clay were calculated for each 

 sample and are plotted in Fig. 9 (see also Appendix 1). This 

 presentation suggests that most samples contain approximately equal 

 proportions of silt- and clay-sized particles and the mean grain size is 

 largely a function of the amount of sand in the sample. 



Consideration of grain size distributions and sorting coefficients 

 does not in itself fully characterize the finer sediments of Casco Bay. 

 Our experience in taking grab samples shows that the sediments are also 

 extremely soft, i.e. have a very low bearing strength. Repeated 

 lowerings of our specially modified grab often failed to obtain a 



