Book

Geologic evolution of Trail Ridge eolian heavy-mineral sand and underlying peat, northern Florida

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Abstract

Trail Ridge ilmenite-ore sand is eolian in origin. Underlying freshwater-swamp peats are the same age, and sand impurities in peat record the approach of the dune. The original alteration state of detrital heavy minerals is preserved in the peat also. This book discusses the geologic evolution of Trail Ridge eolian heavy-mineral sand and underlying peat.
... Trail Ridge was formed (144 Ma) as a barrier island complex during higher sea levels (Force and Rich 1989;Adams et al. 2010). It runs 160 km parallel to the coastline from near Hoboken, Georgia to the vicinity of Starke, Florida. ...
... Rivers passing from the Upper Coastal Plain to the Atlantic bisect the ridge in several places. Trail Ridge is composed largely of marine sands that are high in titanium oxide (Force and Rich 1989), and this is the reason the ridge is attractive for mining. The ridge has been extensively mined for decades farther south in Florida, from Interstate 10 down to Starke, FL. ...
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Defining the upslope extent of Federal Clean Water Act jurisdiction over wetlands and streams has been contentious since the passage of the Act but has large effects on the type, number, and area of wetlands that are protected by legislation. Federal jurisdictional guidance in the US has changed and evolved in response to scientific knowledge, US Supreme Court decisions, and policy goals of Presidential Administrations. In 2020, the Trump administration replaced the Obama administration Clean Water Rule with the Navigable Waters Protection Rule with the goal of reducing jurisdiction over so-called isolated depressional wetlands (wetlands with no connections to obvious stream channels) and ephemeral streams. Here we use a case study of a titanium sands mining proposal on Trail Ridge southeast of Okefenokee Swamp to illustrate the large reduction in wetland and stream protection engendered by this policy change. Under the Navigable Waters Protection Rule, all seven wetlands within the 232 ha mining area, totaling 131 ha or 56 % of the project area, were deemed non-jurisdictional and thus the project required no federal review or permitting. Under an earlier mining application under the Clean Water Rule, all of these same wetlands were declared jurisdictional. Trail Ridge is located on the Atlantic Coastal Plain, an ecological province rich in depressional wetlands and ill-defined surface drainages. This case study shows that in such environments, application of the Navigable Water Protection Rule allows destruction of large numbers and areas of ecologically significant wetlands.
... Heavy minerals were concentrated during marine transgressions, according to Garnar and Stanaway (1994), only in conjunction with other factors such as aeolian winnowing by the wind and resultant heavy-mineral concentrations in aeolian dunes. Accordingly, some of the major heavy-mineral deposits are thought to have important aeolian contributions; examples are Trail Ridge and the western portion of the Green Cove Springs deposits (Force and Rich, 1989;Rose, 2005). Other concentration factors also can come into play. ...
... Analogs exist between modern sediments exposed along the St. Marys and Bells rivers at the Georgia-Florida border and the sediments of the heavy-mineral deposits of the Coastal Plain. For example, the beach ridge sands at Reids Bluff overlie stumps of a freshwater cypress swamp ; Figure 8) much as the beach-ridge sands of Trail Ridge overlie freshwater lignitic peat that contains stumps in upright positions (Force and Rich 1989;Rich, 1985;Rich and Pirkle, 1993). The outcrops at Roses, Reids, and Bells bluffs along the St. Marys River provide excellent examples of some of the major facies associated with heavy-mineral sand deposits of the Atlantic Coastal Plain, and will be discussed in later portions of this paper. ...
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Pirkle, F.L.; Pirkle, W.A., and Rich, F.J., 2013. Heavy-mineral mining in the Atlantic Coastal Plain and what deposit locations tell us about ancient shorelines. Economic mining of heavy-mineral sands has a long history in the Atlantic Coastal Plain. From the early part of the 20th century to date, a total of 11 heavy-mineral ore bodies either have been or currently are being mined in Florida and Georgia. Additional deposits have been lost to mining, primarily due to cultural events, or are waiting future exploitation. These deposits have different origins, as has been seen during recent evaluations of the deposits, some in contrast to conventional depositional models. It has long been believed that deposits formed along shorelines at the height of major marine transgressions, but it is now postulated that some heavy-mineral-bearing sands accumulated on regressional beach ridge plains during periods of temporary stillstands or during slight transgressions that accompanied general marine regressions. Although many deposits might indeed have formed as conventional beach placers, others might have accumulated as deposits associated with fluvial–deltaic regimes or with vegetational baffles. These different origins are reflected in the chemical and physical characteristics of the deposits as well as grain size of the sediment. The relationship of the heavy-mineral mineral deposits (location) to the landforms in the Atlantic Coastal Plain provides insight into the ancient shorelines of the Atlantic Coastal Plain.
... Elevations range from 60 m above mean sea level (asl) along the crest of the ridge to 30 m asl near the toe. The feature is associated with a sea-level high stand and is considered to be either a relict barrier island sequence (White, 1970), a relict beach ridge (Pirkle, 1972), or a large aeolian dune (Force and Rich, 1989). ...
... Trail Ridge is comprised of siliciclastic sediments deposited in a coastal marine environment with a large aeolian component in the upper 8 m (Pirkle and Yoho, 1970;Pirkle, 1975;Pirkle and Czel, 1983;Force and Garnar, 1985;Force and Rich, 1989). These siliciclastics, which are predominately quartz sand, sit on a~4-m-thick brown lignite unit of Pliocene or early Pleistocene age (Rich, 1985). ...
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For the first time, electron spin resonance optical dating (ESROD) has been conducted on littorally transported and aeolian siliciclastic sediments in Florida. ESROD utilizes light-sensitive radiation-sensitive defects at silicon sites that have been replaced by aluminum and titanium atoms to give rise to a time-dependant signal. These defects saturate at higher levels of radiation dose, compared to optically stimulated luminescence, and therefore extend the optical dating range back into the millions of years. Our results show that the Trail Ridge Sequence is a multi-depositional unit that began deposition around 2.2 Ma and continued until 6 ka. The Osceola Cape, of the Effingham Sequence, was deposited around 1.5 Ma, and the Chatham Se-quence was a multi-depositional terrace with at least three events preserved.
... Although glacial onset and retreat reorganized drainages during the time of Trail Ridge deposition, northern Florida is still interpreted to have received sediment from the southern Appalachians (Blum et al. 2019). However, Trail Ridge has been interpreted as a relict Pleistocene shoreline feature with an aeolian component (Force and Rich 1989); as such, sands comprising it may not be relatable to modern or previous drainage networks. ...
... Rivers passing from the Upper Coastal Plain to the Atlantic bisect the ridge in several places. Trail Ridge is composed largely of marine sands that are high in titanium oxide (Force and Rich 1989), and this is the reason the ridge is attractive for mining. The ridge has been extensively mined for decades farther south in Florida, from Interstate 10 down to Starke, FL. ...
Preprint
Full-text available
Defining the upslope extent of Federal Clean Water Act jurisdiction over wetlands and streams has been contentious since the passage of the Act but has large effects on the type, number, and area of wetlands that are protected by legislation. Federal guidance in the US has changed and evolved in response to scientific knowledge, Supreme Court decisions, and policy goals of Presidential Administrations. In 2020, the Trump administration replaced the Obama administration Clean Water Rule with the Navigable Waters Protection Rule with the goal of reducing jurisdiction over so-called isolated depressional wetlands and small streams. Here we use a case study of a titanium sands mining proposal on Trail Ridge southeast of Okefenokee Swamp to illustrate the large reduction in wetland and stream protection engendered by this policy change. Under the Navigable Waters Protection Rule, all seven wetlands within the 232 ha mining area, totaling 131 ha or 56% of the project area, were deemed non-jurisdictional and thus the project required no federal review or permitting. Under an earlier mining application under the Clean Water Rule, all of these wetlands were declared jurisdictional. Trail Ridge is located on the Atlantic Coastal Plain, an ecological province rich in depressional wetlands and ill-defined surface drainages. This case study shows that in such environments, the Navigable Water Protection Rule will allow destruction of large numbers and areas of ecologically significant wetlands.
... The Trail Ridge and Folkston deposits are located along a >200-km-long Pleistocene ridge extending from northern Florida to southern Georgia, oriented parallel to the Atlantic Coast. This ridge was likely once a barrier island (Force and Rich, 1989). Parts of these deposits are actively being mined for ilmenite, rutile, and zircon. ...
Article
We combined geophysical, geochemical, mineralogical, and geological data to evaluate the regional presence of rare earth element (REE)−bearing minerals in heavy mineral sand deposits of the southeastern U.S. Coastal Plain. We also analyzed regional differences in these data to determine probable sedimentary provenance. Analyses of heavy mineral separates covering the region show strong correlations between thorium, monazite, and xenotime, suggesting that radiometric equivalent thorium (eTh) can be used as a geophysical proxy for those REE-bearing minerals. Airborne radiometric data collected during the National Uranium Resource Evaluation (NURE) program cover the southeastern United States with line spacing varying from ∼2 to 10 km. These data show eTh highs over Cretaceous and Tertiary Coastal Plain sediments from the Cape Fear arch in North Carolina to eastern Alabama; these highs decrease with distance from the Piedmont. Quaternary sediments along the modern coasts show weaker eTh anomalies, except near coast-parallel ridges from South Carolina to northern Florida. Prominent eTh anomalies are also observed over large riverbeds and their floodplains, even north of the Cape Fear arch where surrounding areas are relatively low. These variations were verified using ground geophysical measurements and sample analyses, indicating that radiometric methods are a useful exploration tool at varying scales. Further analyses of heavy mineral separates showed regional differences, not only in concentrations of monazite, but also of rutile and staurolite, and in magnetic susceptibility. The combined properties suggest the presence of subregions where heavy mineral sediments are primarily sourced from high-grade metamorphic, low-grade metamorphic, or igneous terrains, or where they represent a mixing of these sources. Comparisons between interpreted sources of heavy mineral sands near the Fall Line and igneous and metamorphic Piedmont and Blue Ridge units showed a strong correspondence with rocks closest to the Fall Line and poor correspondence with rocks farther inland. This strongly suggests that the primary source of those heavy minerals, especially monazite, is the rocks that formed the rocky coast that was present during opening of the Atlantic Ocean, which in turn indicates the importance of coastal processes in forming heavy mineral sand concentrations. Furthermore, narrow radiometric eTh and K anomalies are associated with major rivers, indicating limited spatial influence of fluvial processes. Later coastal plain sediment deposition appears to have involved reworking of sediments, providing an “inheritance” of the rocky coast composition that persists for some distance from the Fall Line. However, this inheritance is reduced with distance, and sediments within ∼100 km of the coast in Georgia and Florida exhibit properties indicative of mixing from multiple sources.
... Some aeolian deposits contain substantial concentrations of HM. Aeolian processes created many of the world's largest fossil and recent heavy-mineral deposits, such as: 1) the Guaju HM (ilmenite-dominant) deposits on the eastern coastal area of Brazil (Sabedot and Sampaio, 2006); 2) Late Holocene aeolian HM backshore dune deposits on the southern coast of Brazil (Dillenburg et al., 2004); 3) the Grande Côte HM deposit, a mobile dune field about 100 km long bordering the Senegal coast (Mineral Deposits Limited, 2016); 4) the highly productive Richards Bay area HM deposits (zircon, rutile, and ilmenite hosted in dune sands) on the east coast of South Africa (Richards Bay Minerals, 2013); and 5) DuPont's Trail Ridge HM deposits hosted in a Pliocene dune field in north-central Florida (Force and Rich, 1989). ...
Article
The processes leading to the formation of beach placer deposits generally begin inland and terminate at the coast, including source rocks being weathered, eroded and then transported by streams and rivers to the coast, where the sediments are deposited in a variety of coastal environments. The coastal sediments are reworked by the action of waves, tides, longshore currents and wind, which are effective processes for sorting the mineral grains based on differences in their size and density, resulting in laminated or lens-shaped packages of sediments up to tens of meters thick that are rich in heavy minerals. Detailed studies of sedimentary basins, as well as peripheral (paleo-)valleys that drained sediment source areas, are important tools in the exploration for heavy mineral resources. Knowledge of the (paleo-)basin, associated valley architecture and the source of heavy minerals concentrated in the shorelines and valleys are useful guides to the potential for, and location of, economic deposits. Evidence from sedimentology can be combined with that from other geological and geophysical characteristics to arrive at a general reconstruction of basin and paleovalley architecture and depositional environments. Complex paleogeography of the shorelines can influence or determine the sites of heavy mineral concentration. Heavy mineral sands tend to concentrate in certain shoreline settings during storm activity. Repeated storm erosion and reworking over centuries (e.g., the southeastern coast of Australia) or millennia (e.g., the Eucla and Murray Basins of Australia) can progressively enrich heavy mineral sand deposits. Preservation of these deposits over a geological timeframe of millions of years can ensue through subsidence of coastal sediments, and during sea-level change that results in either shorelines migrating inland (marine transgression) or seaward (marine regression), potentially burying or stranding earlier deposits or reworking them to form younger deposits. Refinements in remote sensing and geophysical techniques, data processing, sedimentology and computer-aided interpretations provide effective, economic and efficient methods for modeling coastal reconstructions and for exploring provinces and terrains prospective for heavy mineral sand deposits. Landscape topography analysis, combined with geophysical methods that can resolve physical property contrasts between the shoreline sediments and underlying sequences, are increasingly used in mineral exploration to locate and to reconstruct paleoshorelines and paleovalleys. Australia has modern and ancient beach-placer deposits, both of which show many similar geologic features. The formation of these heavy mineral deposits provides one of the best examples of applying knowledge of modern systems (e.g., the west and east coasts of Australia) as an analogue to interpret and understand the geology and form of ancient deposits (e.g., the Eucla and Murray Basins of southern Australia). This study provides descriptive and exploration models of Australia’s heavy mineral sand deposits formed in coastal environments, which can be applied to similar settings worldwide.
... The total content of heavy minerals significantly increases up the section (from 126 to 248 kg/ton in the Khuzhir sequence and from 230 to 460 kg/ton in the Peschanka sequence). Force and Rich (1989) noted an increase in ilmenite content in blown sands of the Trail Ridge placer on the USA Atlantic coast. According to Patyk-Kara et al. (2001), ilmenite concentrates of the upper beds of Ti-Zr placers, which undergo blowing and weathering, are almost ubiquitously enriched in TiO2 as compared with underlying beds. ...
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This study is concerned with the eolian deposits on the Baikal shore. It has been established that (1) the eolian sands are distinctly divided into two sequences: Khuzhir (Late Pleistocene) and Peschanka (Holocene); (2) the ilmenite enrichment of the sands is due to the removal of sand grains (containing mainly light minerals) by strong winds up the shore, first, from a dewatered beach zone, and then, from zones of psammitic-material transition. This leads to the concentration of ilmenite and other heavy minerals, first, within the beach zone, and then, within the zones of prevailing eolian-sand transition. The accumulation-transition zones are most enriched in heavy minerals, including ilmenite; (3) the ilmenite content in the study Ti-ore placer deposit shows a high correlation (R = 0.89) with the total content of heavy minerals.
Chapter
The study delineates the heavy mineral enrichment of beach sands situated along the eastern coastal areas of India, which has been extensively studied for its economic resources. The results obtained are discussed in terms of radioactive element and rare earth element (REE) concentration in the study area. Certain radiological attributes like radium equivalent, absorbed dose rate, and annual effective dose rate values have been presented. In the study area, the average Th/U ratio is found to be about 22. The absorbed dose rate and the thorium concentration show a positive correlation. The average TREE concentration varies between 774 and 1066 ppm with an average of about 6749 ppm. The TREE and thorium concentrations show a good concordance, which is indicative of the fact that these are sourced primarily from the radioactive mineral monazite. This is important as the strategic and critical minerals, specifically the rare earths, are primarily extracted from naturally occurring radioactive minerals like bastnaesite, monazite, and loparite, all of which are primarily radioactive in nature. The study discusses the effect of lacustrine and estuarine environment on the heavy mineral deposition, enhancement along the beach placers, and its implications. The effect of consistent mining along the beach area on the elevated radioelement concentration as well as the beach geomorphology has been discussed. Additionally, the chapter also highlights the disruption caused by the dredging activities to the marine species dwelling along the beach areas.
Article
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Major world ilmenite and rutile accumulations reveal similar regional geology and Proterozoic age deeper crustal source rocks. During crustal collision titanium crystallizes as ilmenite and rutile at buried sites of high pressure and temperature rock metamorphism. Hydrothermal activity can convert titanium minerals to rutile, but titanium migration and enrichment seem only local. Many melts crystallize rocks with iron-titanium oxides in solid solution, but titanium enrichment at economic scale takes place in basic intrusive melts often associated with anorthosites and charnokite. Sedimentary placer enrichments have formed since the Proterozoic with water-resistant ilmenite, and rutile segregating by gravity from quartz sands deposited from flowing water. Placers have residual, alluvial, strand and shallow marine variants. Time, organic acids, and sand permeability play lead roles in the leaching of iron from ilmenite during weathering and diagenesis.
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The current state of placer research may be regarded as a transition from the descriptive mineralogy, including the study of typomorphic properties of minerals and their assemblages, to probing fine mechanisms of ore material migration in placers and the creation of quantitative models that describe an inhomogeneous multidimensional space of placer deposits taking into account regional and local factors. Placers are complex geochemical systems where the concentration of most resistant minerals is accompanied by a conversion of their physical and chemical properties that affects the quality of ore, its dressability, and fields of usage. In this work, data on specific (tin, rare metal, gold, and complex titanium–zirconium) placers are used to define the current objectives of placer mineralogy and possibilities of their realization in the study of (1) placer mineral assemblages and their modification during the placer formation, (2) primary typomorphic features of minerals as guides for provenance and placer evolution, (3) acquired typomorphic features indicating the placer formation conditions, and (4) environmental and technological aspects of placer mineralogy.
Article
Heavy mineral placer deposits of Pleistocene age in northeastern Florida were examined sedimentologically.Neither general setting, nor granulometric or mineralogic results are in agreement with a concentration of the heavy minerals in a beach, eolian or fluvial environment.Granulometric moment parameters of the ore sands seem to be distinctive. They include moderate sorting, high positive skewness, high kurtosis and a distinctive fine tail. Similarities of grain size curves of the placer sands with nearshore-offshore sands exist.Mineralogically the samples are more variable but always impoverished in epidote. This scarcity of epidote is atypical for eolian sediments in the study area, and the lack of garnet and the fineness of ore sands are uncommon for beach placers of northeast Florida.Underlain by dune ridges, which acted as obstacles on the shallow sea floor during the Penholoway transgression (1.3 ± 0.1 Ma B.P.), heavy minerals in the Boulogne and Green Cove Springs main ore body must have been concentrated in bars by the interplay of longshore and transverse bottom currents. Lighter heavy minerals were deposited in smaller nearshore bars closer to the former coast (Green Cove Springs small ore body) or in dunes of barrier islands (Green Cove Springs western ore body). As is true today, layers of noteworthy concentrations of economic minerals in the swash zone of Florida beaches were formed only rarely during storms, contrary to the coasts of Australia or India, where higher energetic conditions prevail.The proposed model of concentration of heavy minerals in certain outer nearshore bars has long been assumed but never been proven.
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