Studies on water movements and sediments in Southern Lake Michigan : part 1[-3] ... / by John C. Ayers.

and was derived from the detailed field sheets (boat sheets) of
the U. S. Lake Survey. This bathymetry represents the bestpossible -synthesis of all the sounding data of the Lake Survey
up to the present. The depth-contour interval is 50 feet.
Figure 2 presents Hough's 1935 sediment map, reproduced
without latitude-longitude lines or state lines. It is also
without three 90-fathom depth contours in the deepest portion,
these depths having proven to be false.
The bathymetry of Figure 2 was constructed by Prof. Hough in
the early 1930's and represents the then best-possible synthesis
of the Lake Survey data of that time. The depth-contour interval
of this figure is 10 fathoms.
Figure 3 presents the results of our bottom sediment survey.
It is necessary to explain here certain aspects of the preparation
of this map.
The edges of the several sediment types in Figure 3 have been
placed halfway between the pairs of differing samples that require
a boundary somewhere between them. Probably a certain amount of
error in the positioning of boundaries has resulted from this
practice.
In the north-central portion of the basin, where boundaries
appear to cross the basin but where additional samples are needed,
question marks along the boundaries indicate our uncertainty as
to their locations.
This map was prepared from the field descriptions of sediment type(s). By "field description" is meant a phenotypic description based upon combined visual inspection, testing for odor,
and feeling of the sediment with the fingers. Field description

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