--> Abstract: Eocene-to-Miocene Karst Seismic-Sag Structural Systems, Southeastern Florida Platform, by Kevin J. Cunningham, Cameron Walker, and Jeffrey N. King; #90124 (2011)
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AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA

Eocene-to-Miocene Karst Previous HitSeismicNext Hit-Sag Structural Systems, Southeastern Florida Platform

Kevin J. Cunningham1; Cameron Walker2; Jeffrey N. King1

(1) U.S. Geological Survey, Fort Lauderdale, FL.

(2) Walker Marine Geophysical Company, Boca Raton, FL.

High-resolution, multichannel, Previous HitseismicNext Hit-reflection profiles recently acquired in and east of Biscayne Bay, and in canals of southeastern peninsular Florida, exhibit numerous vertically arranged sags and disruptions in reflections. In the study area, a southeastern part of the Florida Platform, the Previous HitverticalNext Hit features occur within mostly Eocene-to-middle Miocene karsted carbonates and uncommonly in upper Miocene siliciclastics. The sags are buried by upper Miocene-to-Holocene sedimentary rocks and sediments; however, they likely manifest as well-documented sinkholes along the submarine surface of the Pourtales and Miami Terraces. The Previous HitverticalNext Hit sags and disruptions in reflections are interpreted to be suprastratal deformation above collapsed paleocaves or collapsed paleocave systems, and represent (1) fractures; (2) faults; (3) narrow (hundreds-of-m-scale wide) Previous HitseismicNext Hit-sag structural systems; and (4) broad (km-scale wide) Previous HitseismicNext Hit-sag structural systems. Maximum height of the karst structures has been measured up to about 500 m; however, some may extend deeper, but no reliably interpretable stratal patterns exist within chaotic reflection-Previous HitseismicNext Hit configurations that prevail within the lower part of the Previous HitseismicNext Hit profiles. At most, the Previous HitverticalNext Hit relief on the sags is about 50 m. Commonly the Previous HitseismicNext Hit-sag structural systems are multistoried, exhibited as a Previous HitverticalNext Hit arrangement of cyclic zones of sagging reflections that suggest a progressive evolution from (1) cave formation; (2) cave collapse; (3) suprastratal sag; and (4) in some cases, final infill of the upward termination of sag zones. The Previous HitseismicNext Hit imaging provides clues as to the sealing capacity of confining units within the carbonate Floridan aquifer system. Faults or fractures or both associated with the large-scale, Previous HitseismicNext Hit-sag structures may promote the Previous HitverticalNext Hit flow of groundwater across relatively low-permeability carbonate strata that separates aquifers or subaquifers. Previous HitSeismicNext Hit-sag structures, and associated faults and fractures could act as regional “confinement” bypass systems. Preliminary numerical modeling in southeastern Florida corroborates the suggestion that “confinement” bypass systems act as potential pathways for the Previous HitverticalNext Hit migration of groundwater across relatively low-permeability carbonate strata within the Floridan aquifer system. The Florida Previous HitseismicTop-sag structures provide an excellent analog for karst-related migration of hydrocarbons across seals in platform carbonate reservoir systems.