Another "factor" that crossed my mind a number of times that could
explain other deposits ("sub floor too") is movement. Various historic
sites have been moved! The Valentine House in the Bronx was moved
across the street to preserve it, the former location of the Society
for the Preservation of Long Island Antiquities had a building moved
onto it and there in the ground were found six or more "half" Spanish
doubloons! Also I was thinking of the various stages the New York
signer of the American "Declaration of Independence" the William Floyd
Manor house, has been documented to have been built in, and perhaps
former activities areas later have construction over them of course.
Various sites have gone through the "summer kitchen" phase perhaps
(except in Harpers Ferry, VA where the second story kitchen's flue was
"pulled" out of the stratified shale deposit in the slope behind the
houses, leaving today hollowed out outlines of former chimney flues
and hearths floating "mysteriously" up in the geologic "walls" or cuts
behind the houses. The Roe Tavern I wrote about apparently was "way
back" also moved across the street and a public park is on the
original site. So perhaps if one was excavating "sub-floor" deposits
for it, a previous structure's deposits would be encountered.

George Myers