55_ 



The middle reach shared characteristics of both the upper and outer river zones. 

 Similar to the upper region, the middle samples contained plant fragments and fecal 

 pellets. Similar to sediment cores at the mouth of the river, the middle region contained 

 similar quantities of rock fragments and texhired ostracods. However, in contrast to both 

 the upper and outer zones of Royal River, the fine fraction samples for the middle zone 

 contained a variety of insect parts, and no fly ash. 



Microfossils. The microfossils in the Royal River cores also served to differentiate 

 the upper and outer zones of the Royal River. In general, the microfossil assemblage in 

 the upper reach cores consisted primarily of mudflat foraminifera and thecamoebians. The 

 number of individual thecamoebian species decreased with distance from the upper reach. 

 Cores from the outer reach were dominated by mudflat and marsh foraminifera, while 

 samples from the middle reach, as with mineralogical analyses, resulted in a combination 

 of the two end member assemblages. Raw data from microfossil analyses is provided in 

 Appendix B. 



Samples from many of the cores collected in the upper reach resulted in a low 

 overall abundance of microfossils counted in ten trays of material. For example, RR-7 

 contained only 3 freshwater thecamoebians, RR-8 contained 16 mudflat foraminifera and 

 27 thecamoebians (Figure 4-2), and sediment from RR-15 did not contain any microfossils, 

 probably because it consisted of coarse sand which is inhospitable to foraminifera and 

 thecamoebians. One of the additional upper reach cores analyzed, RR-6, had significantly 

 higher numbers of microfossils, with 127 foraminifera and 25 thecamoebians picked in 3 

 trays (Section 4.6). The percentage of thecamoebians increased with the proximity of the 

 core location to the upper river region. Core RR-6, analyzed as part of the additional core 

 analysis (Section 4.6), was also different from the other upper reach cores in that shelf 

 calcareous and agglutinated foraminifera specimens were present. One of the shelf 

 agglutinated species in RR-6, Martinotiella communis, was not seen in any of the prior 

 samples from the Royal River or at the PDS. The difference in microfossil abundance in 

 RR-6 and the other additional cores are discussed further in Section 4.6. Shelf species 

 were also noted in RR-18 and RR-26 (Appendix B); the trace appearance of shelf species 

 has important implications in the interpretation of the cores collected from the dredged 

 material deposit. 



A lack of microfossils was also noted in some of the cores collected in the middle 

 (RR-10, RR-29) and outer (RR-21) reaches. The low number of individuals counted tends 

 to decrease the accuracy and reliability of the relative abundance calculations for those 

 cores. As noted in Section 3.1.2, a methanol solution was used to preserve all microfossils 

 samples from the sediment cores collected as part of the Royal River survey, and was 

 shown to be less effective than the formalin preservative used for grab and core samples at 

 the PDS site (Section 4.6). 



The Portland Disposal Site Capping Demonstration Project, 1995-1997 



