  This investigation addresses the discovery of a proposed impact crater
located off the coast of Miami, FL under the North Atlantic Ocean. A
preliminary analysis of bathymetry data obtained from the National Oceanic and
Atmospheric Administration implied a morphology consistent with a complex
crater produced by a hypervelocity impact event of extraterrestrial origin. The
proposed impact features include a central peak, concentric rings, and an
ejecta field to the northwest. Analysis of geological data from the US
Geological Survey places the strata overlying the proposed impact site as Miami
Limestone, Pleistocene, accumulated during Marine Isotope Stage 5e, thereby
placing the maximum age of the proposed impact crater at 80 ka to 130 ka. Three
other competing hypotheses for the formation of the structure, namely a
controlled maritime explosion, radial lava flow from volcano, or a depressed
bioherm, doline, or karst (solutional depression) were explored throughout the
investigation. To confirm the proposed structure as an impact crater, an
in-situ underwater expedition was organized by Planetary Sciences, Inc.
specifically to ascertain whether planar formations, shatter cones, and shock
metamorphic and or other meteoritic properties were present. After analyzing
the geological samples collected at the proposed impact crater, examining the
morphology of analogous geologic structures, and evaluating competing
hypotheses, we conclude that the structure is a solutional doline formed by the
uneven dissolution of the Miami Limestone, and, accordingly, do not recommend
that the structure be indexed in the Earth Impact Database
