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Subsidence Investigation SDII Project N�.imber•3023547 Quiros-Martinez Residence-Zephyrhills,Florida 1.8 Review of Published Regional Geologic Conditions This regional geology section was developed from a number of regional geologic: investigations and is intended to provide a context for understanding the geology of the are:t in which the residence is located. The study site is located within the Zephyrhills Gap Physiographic Province o f Florida. This province links the Western Valley and Gulf Coastal Lowlands Physiographi,; Provinces of Florida.4 Land surface elevations in this region range from approximately 40 to 100 feet above sea level.`The gentle slopes of the terrain reflect the Penholoway and Wicomico rnarine terraces, which were fonned by changes in sea level during the Pleistocene Epoch. In this region, three major geologic formations occur at or near the land aurface. These formations have influenced the development of soils and karst in the area. They ,are, in order of youngest to oldest, undifferentiated Plio-Pleistocene sediments, the Miocene Hawthorn Group and the Oligocene Suwannee Limestone. The undifferentiated Plio-Pleistocene marine terrace sediments are composed of Iine to medium quartz sands with varyi�zg amounts of clay matrix. The sediments are usually gray to brownish in color and poorly to moderately consolidated. Beneath the surface cover that comprises the Zephyrhi(is Gap is the Miocene Ha�wthorn Group.6 The Hawthorn Group sediments generally consist of gray to grayish-brown or reddish-brown, poorly to moderately consolidated sand, clayey sand, and clay. Throughout the re�,ion, individual formations of the Hawthorn Group are undifferentiated due to intense weatherin� and erosion of the Miocene cover. T}�e Oligocene Suwannee Limestone generally lies below the Miocene cover in t:he region. The upper portion of this limestone has been subjected to weathering during repeat�;d episodes of subaeriai exposure as sea level fluctuated in the geologic past. This weathering o;the limestone has led to the creation of an epikarst surface. Examples of weathering feature:; found on the epikarst surface include solution-enlarged fractures, solution holes, and limestone�:iinnacles. Sinkhole activity in this geologic setting is controlled to a large extent by the thickness of the depositional cover over the limestone. This cover is typically thin and poorly consclidated. When sinkholes do occur, they are generally few, shallow and broad, and develop silowly.� In this region, low-resistance materials and losses of drilling fluid circulation dtiring standard penetration tests are often related to shallow weathering or erosional features �it or near the epikarst, or with ancient erosional features near strata contacts. °Puri,H. S.and R.0.Vernon. 1964 Summary of the Geology of Florida and Guidebook to the Classic Exposures. F'lorida Geological Survey Special Pubiication No. 5(revised).312 p. 5 Healy,Henry G 1975.Terraces and Shorelines of Florida.Plorida Bureau of Geology Map Series No 71 6 Scott,T M.,K.M.Campbell,F.R.Ruperl,.T D Arthur,T M Missimer,J M.Lloyd,J W Y�n,and.T G. Duncan.2001 Geologic Map of the State of Florida. Florida Geological Survey,Map Series No. 14b. 'Sinclair,W C. and J W Stewart. 1980 Sinkhole Type,Development and Distribution in Fiorida. I�forida Bureau of Geology Map Series No. 110 1-4