Close-up, of fusulinid limestone slab from Worland Limestone
This close-up of a small area (12 mm wide by 13 mm high)
at the middle
left of the slab shows most fusulinids with approximately transverse
sections. Two of the fusulinids display close to longitudinal sections (top
middle and the very dark specimen at upper right). Nevertheless, the
orientation of fusulinid tests is clearly preferential, with most long axes
close to horizontal and going into the slab. The elongate particle in the
upper right is an algal plate. Preferential orientation of sediment particles
is normally the result of current flow or oscillatory wave action. However,
note that the two longitudinal sections are in nearly vertical orientation,
which would not likely result from current action. The preferential
orientation is therefore more likely the result of bioturbation, whereby
burrowers pulled adjacent sediment along with them, aligning the
elongate fusulinids in the same direction they moved. Alternatively, the
burrowers may have ingested the fusulinids, which then moved through
the burrowers' gut with long dimension parallel to the gut. Upon excretion,
the tests remained in that orientation or were "dumped" into varied
orientations, including vertical.
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