Origin and development of true karst valleys in response to late Holocene sea‐level change, the Transverse Glades of southeast Florida, USA

Abstract

The Miami Limestone is an oolite depositional body that is used as an analog model for geological interpretation of the rock record. Barrier‐bar complex, oolite banks, extensive bryozoan flats and tidal creeks, referred to as transverse glades, have been described. High‐resolution LiDAR data are used to produce unprecedented, detailed topographic maps of the transverse glades in the southern Atlantic Coastal Ridge. These maps were originally used to calculate historic discharge from the Everglades but revealed features inconsistent with the prevailing theory that the topography is of a depositional origin. Field observations verified an epikarst terrain truncated by collapsed subsurface conduits creating valleys, previously described as palaeotidal creeks. Observations of the 12 southern tidal creeks or transverse glades provided a sequence of six stages in the development of these karst valleys. After Late Pleistocene deposition of the Miami Limestone, sea‐level dropped producing conditions of: (a) epikarst which reduced the surface elevation preferentially, forming the southern Everglades Basin and modifying Biscayne Bay and Florida Bay precursor basins and (b) downward water movement producing vertical solution features. As Holocene sea‐level approached the South Florida carbonate platform margin a freshwater lens formed and groundwater movement became horizontal. Two sets of cavernous zones developed during the Middle and Late Holocene. Solution pipes and dolines provide a connection between the surface and groundwater along alignments which delineate subsurface conduits. Stages of valley formation are associated with the collapse of these conduits first forming a series of pocket valleys followed by narrow blind valleys and half blind or through valleys linking the Everglades to the coastal plain. Valleys then expanded in width until: (a) completion of cavernous zone collapse, (b) most boulder fields and valley margins reduced by weathering and (c) the valleys filled with wetland soils.

Impact of facies and diagenetic variability on permeability and fluid flow in an oolitic grainstone—Pleistocene Miami Oolite

“…Florea et al () successfully demonstrated the use of electrical resistivity tomography to delineate the small caves within the barrier bar and infer whether they were air filled or water filled. The ‘young’ outcropping surface of the MO as viewed on the high‐resolution airborne LiDAR DTM is indeed insightful from a depositional perspective as shown by the quantitative comparison to modern counterparts by Purkis and Harris (), but at the same time the DTM and select outcrops (Figure D) show a depositional surface that is locally modified by surficial karst features, primarily dolines and a few shallow caves as shown in Figure (Halley and Evans, ; Cressler, ; Florea et al , , ; Cunningham and Florea, ; Harris et al , ; Meeder and Harlem, ). Harris et al () analysed the dolines for their size and depth, their lateral distribution and relationship to depositional topography, and the separation distance between them.…”

“…narrow valleys or channels in which the soils and vegetation are similar to those in the Everglades) (Cunningham et al , ; Florea et al , ). Meeder and Harlem () propose that the palaeo‐tidal channels are karst valleys, being entirely the product of collapsed subsurface conduits. It is argued here that the similarity in channel characteristics between those of the MO and modern examples from Great Bahama Bank (Purkis and Harris, ), along with depositional facies changes observed from outcrop and core between channel and sand bar (Evans, ; Usdun, ) support a dominantly depositional origin, with subsequent diagenetic modification only serving to widen the channels, locally change their profile, and add dissolution features.…”

The Use and Abuse of Economics in Land Use Decision-Making in South Florida: An Industrial Park & Its Alternatives, 2020-2023

“…The neighborhoods on the north side of the Turnpike would access the park via a pedestrian tunnel beneath the Turnpike. The Nature Preserve section of the park will be accessed from its western side, where visitors will find a Nature Center, the canoe and kayak rental center, and the foot and bike trails that lead through the restored wetlands (Meeder & Harlem, 2019; George Mason University, Center for Regional Analysis, 2018). Visitors may climb up the 15-meter (50-foot) observation tower for bird and wildlife-watching and stroll the extensive boardwalks through the marshes along the Canal to the Bay.…”

The paleo-ecological application of mollusks in the calculation of saltwater encroachment and resultant changes in depositional patterns driven by the Anthropocene Marine Transgression

“…The Late Holocene Southeast Saline Everglades (SESE) oligotrophic wetland environment developed east and south of the Late Pleistocene (Hoffmeister et al, 1967) Atlantic Coastal Ridge (ACR) on the broad, slightly seaward dipping ramp lying below 1.5 m (Figure 1). Transverse glades, erosional breaks in the ACR (Meeder and Harlem, 2019), historically drained the central Everglades basin and maintained freshwater wetlands but today serve as conduits for muchreduced Everglades' flows, including urban and agricultural runoff, to Biscayne Bay. The ramp provides an area for development of wide bands of plant communities and associated facies along the shore-normal salinity gradient, permitting easy recognition of changes associated with SLR driven SWE (Meeder et al, 2017).…”