Proposed Miami Impact Crater Identified as a Solutional Doline of Oolictic Limestone

TL;DR

This study investigated a proposed impact crater off Miami's coast using bathymetric and geological data, but concluded it is a solutional doline formed by limestone dissolution, not an impact crater.

Contribution

The paper provides a detailed analysis combining bathymetric, geological, and expedition data to refute the impact crater hypothesis and identify the structure as a karst formation.

Findings

The structure is a solutional doline, not an impact crater.

Geological analysis showed no meteoritic or shock metamorphic features.

The maximum age of the formation is estimated at 80,000 to 130,000 years.

Abstract

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