Karst‐driven flexural isostasy in North‐Central Florida

Abstract

Deformed marine terraces can be used to explore a region's uplift history. Trail Ridge is a marine terrace in north Florida that is nearly 80 m above modern sea level and contains Quaternary marine fossils, a fact that is inconsistent with estimates of paleo‐sea level history since the early Pleistocene. This implies that the terrace has experienced uplift since its formation, as well as nonuniform deformation recorded by the warping of its previously horizontal state. The Florida carbonate platform, located on the passive margin of eastern North America, is a setting where nontectonic influences (e.g. isostatic adjustment, dynamic topography) can be examined. We present a single‐transect, numerical model of vertical displacement, derived from elastic flexure, to assess the influence of karst‐driven isostatic uplift on present day topography of Trail Ridge in north Florida. Flexural modeling predicts elevations in central Florida not observed today, most likely because surface erosion and karst cavity collapse have obliterated this high topography. Older subsurface stratigraphic units, however, display the arched profile predicted from flexural modeling. Mass loss, calculated by differencing modeled topography and observed topography, was found to be 6.75 × 1012 kg, since emplacement of Trail Ridge. Uplift rates, assuming karst‐driven flexural isostasy alone, using previously estimated ages of Trail Ridge of 0.125, 1.4, 3, or 3.5 Ma were found to be 0.535, 0.048, 0.022, and 0.019 mm/yr, respectively. A more likely explanation of uplift includes contributions from dynamic topography and glacial isostatic adjustment which should be further explored with more advanced geophysical modeling.

Topographic Constraints on the Evolution and Connectivity of Titan's Lacustrine Basins

“…A cryovolcanic interpretation would also fail to account for expansion through uniform scarp retreat, although cryovolcanic processes may act as seed points for initial formation with subsequent growth dominated by other mechanisms. Similarly, other doming mechanisms such as organic diapirs (e.g., terrestrial salt domes), spring mounds, or karst‐driven isostasy (Woo et al, ) may also contribute. The noncircular shapes and dense spatial clustering argues against impact craters, although impacts cannot be ruled out as another potential seeding mechanism.…”

Geoarchaeological Evidence for the Decline of the Medieval City of Qalhat, Oman

“…Another process that needs to be considered is isostatically driven vertical uplift. Coastal uplift as isostatic response to karstification is seen as an important process along the coast of north Florida (Adams, Opdyke & Jaeger 2010;Opdyke et al 1984;Woo et al 2017). Our study area is characterised by intense karstification resulting in an open karst system that includes the large wadis.…”

Uplift of Trail Ridge, Florida, by Karst Dissolution, Glacial Isostatic Adjustment, and Dynamic Topography

“…Elastic flexure associated with karst uplift is not included in the formulation of equation (3), which assumes that isostatic equilibrium prevails (Adams et al, 2010). Woo et al (2017) argued that uplift driven by The variability along each contour is not a numerical artifact and rather reflects the fact that high stands exist at discrete times (see,e.g.,Figures 4(c) and 4(f)). Blue and purple dots on the vertical axes mark the carbonate dissolution efficiencies inferred by Adams et al (2010) and Opdyke et al (1984), respectively.…”

“…These values are reduced to 25% and 45% in the case of an elastic lithosphere of thickness 40 km. It is clear that flexure can produce a significant modulation of the signals shown in Figures 2(d), 3(a), 4(b), and 4(e), as described by Woo et al (2017). However, the magnitude of this modulation will be dependent on the spatial scale of the region experiencing karstification and on the elastic strength of the crust-lithosphere region, which may vary laterally.…”

“…(Additional ESROD dates imply deposition ages of 1.55-1.43 Ma and 1.09 Ma-860 ka for the multigenerational Penholoway and Talbot sequences, respectively, rather than MIS 11 and 5e as predicted by Adams et al, 2010. ) Second, and discussed in turn below, additional regionally important geophysical processes such as glacial isostatic adjustment (GIA; Raymo et al, 2011), dynamic topography (DT; Rowley et al, 2013), and elastic flexure (Woo et al, 2017) contribute to Florida's elevation, though these were not included in the model of Adams et al (2010). While previous studies highlighted the individual contributions of these processes to the present-day elevation of Trail Ridge (Adams et al, 2010;Opdyke et al, 1984;Rowley et al, 2013;Woo et al, 2017), these contributions cannot be considered in isolation and summed a posteriori to reappraise the contribution of karst dissolution to Florida's uplift because elevation change resulting from GIA, DT, and flexure will influence the subaerial emergence of the Florida Platform and, in turn, the volume of subsurface carbonate subject to karstic dissolution and isostatic uplift.…”