Since large numbers of macro and micro invertebrate fossils were found in both coarse and fine grained sediments, it was concluded that substrate was not a very dominant control.  There are, however, two exceptions to this in microfaunal species.  The ostracode, Cytheropteron pseudomontrosiense Whatley and Masson, was found much more commonly in clay sediments, and the foraminifera, Elphidium incertum/asklundi (Williamson)/Brotzen, was typically found in pebbly to sandy sediments.

The following table (Rodrigues) shows the types of sediment in which certain macrofossil associations were commonly found.  The data demonstrates the diversity of the substrate type within a single association.


Sediment Types for Invertebrate Macrofaunal Associations 

Macrofaunal Association


Balanus hameri

Pebbly sand, pebbly sandy clay, pebbly clayey sand

Hiatella arctica, Macoma balthica, Mytilus edulis

Gravel, sand, sandy clay, clayey sand, clay, silty clay

Macoma calcarea

Sandy clay

Mya arenaria

Gravel, sand, clayey sand

Mya truncata

Pebbly clayey sand

Portlandia arctica

Pebbly clay, sandy clay, clay, silty clay


Pebbly sand, sand

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