The Pine Mountain window of Alabama: Basement-cover evolution in the southernmost exposed Appalachians

Steltenpohl, Mark G.

doi:10.1007/978-94-011-1614-5_33

Cited by 7 publications

(11 citation statements)

References 20 publications

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“…Two distinct metamorphic events affected basement rocks of the Pine Mountain terrane (Schamel and Bauer, 1980; and Moore, 1988;Steltenpohl, 1992;Steltenpohl and Kunk, 1993). Mesoproterozoic upper amphibolite-to granulite-facies metamorphism, M 1 , resulted from the Grenville event (Odom et al, 1973(Odom et al, , 1985Steltenpohl and Moore, 1988;Stieve and Size, 1988).…”

Section: Geologic Contextmentioning

confidence: 95%

“…The Pine Mountain Group ( Fig. 2) comprises, from stratigraphic bottom to top, the Hollis Quartzite, Chewacla Marble, and Manchester Schist (Crickmay, 1952;Clarke, 1952;Bentley and Neathery, 1970;Raymond et al, 1988), and these units have been suggested to lithologically correlate, respectively, with the Chilhowee-Shady/ Knox-Rome platformal sequence in the foreland (Clarke, 1952;Sears et al, 1981b;Steltenpohl, 1992;Yokel et al, 1997). Feldspathic schists lying between the Hollis Quartzite and the basement gneiss, the Halawaka and Sparks schists (Clarke, 1952;Raymond et al, 1988), are interpreted as Ocoee rift facies (Clarke, 1952;Bentley and Neathery, 1970;Sears et al, 1981aSears et al, , 1981bSteltenpohl, 1992;Yokel et al, 1997).…”

Section: Geologic Contextmentioning

confidence: 96%

“…First, the Motts Gneiss is sheared into the right-slip Goat Rock fault zone which formed during the late Carboniferous (ca. 288 Ma; Steltenpohl et al, 1992). The elongation lineation within both the Goat Rock fault zone and the Motts Gneiss is coaxial.…”

Section: Geologic Contextmentioning

confidence: 96%

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Gondwanan/peri-Gondwanan origin for the Uchee terrane, Alabama and Georgia: Carolina zone or Suwannee terrane(?) and its suture with Grenvillian basement of the Pine Mountain window

Steltenpohl¹,

Mueller²,

Heatherington³

et al. 2008

Geosphere

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The poorly known, suspect, Uchee terrane occupies a critical tectonic position with regard to how and when peri-Gondwanan (Carolina) and Gondwanan (Suwannee) terranes were sutured to Laurentia. It lies sandwiched between Laurentian(?) continental basement exposed in the Pine Mountain window and adjacent buried Gondwanan crust of the Suwannee terrane. The Uchee terrane has been proposed as both a septum of Piedmont rocks that once was continuous across the erosionally breached Pine Mountain window or part of the Carolina zone. To help resolve this issue, we conducted U-Pb (SHRIMP-RG) (sensitive high-resolution ion microprobe-reverse geometry) zircon studies and whole-rock isotopic analyses of principal metasedimentary and metaplutonic units. U-Pb ages for zircons from the Phenix City Gneiss suggest igneous crystallization at ca. 620 Ma, inheritance ca. 1000 to ca. 1700 Ma, and a ca. 300 Ma (Alleghanian) overprint recorded by zircon rims. Zircons from the metasedimentary/metavolcaniclastic Moffi ts Mill Schist yield bimodal dates at ca. 620 and 640 Ma. The 620 to 640 Ma dates make these rocks age-equivalent to the oldest parts of the Carolina slate belt (Virgilina and Savannah River) and strongly suggest a Gondwanan (Pan-African and/or Trans-Brasiliano) origin for the Uchee terrane. Alternatively, the Uchee terrane may be correlative with metamorphic basement of the Suwannee terrane. The ca. 300 Ma overgrowths on zircons are compatible with previously reported 295 to 288 Ma 40 Ar/ 39 Ar hornblende dates on Uchee terrane rocks, which were interpreted to indicate deep tectonic burial of the Uchee terrane contemporaneous with the Alleghanian orogeny recorded in the foreland. Temperaturetime paths for the Uchee terrane are similar to that of the Pine Mountain terrane, indicating a minimum age of ca. 295 Ma for docking. In terms of tectono-metamorphic history of the Uchee terrane, it is important to note that no evidence for intermediate "Appalachian" dates (e.g., Acadian or Taconian) has been reported. This younger history, together with the ages of metaigneous rocks and evidence for pre-Grenville basement, suggests the Uchee terrane is likely of Gondwanan origin and may be related to Carolina zone terranes that accreted during the Alleghanian orogeny.

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Section: Geologic Contextmentioning

confidence: 95%

Section: Geologic Contextmentioning

confidence: 96%

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Gondwanan/peri-Gondwanan origin for the Uchee terrane, Alabama and Georgia: Carolina zone or Suwannee terrane(?) and its suture with Grenvillian basement of the Pine Mountain window

Steltenpohl¹,

Mueller²,

Heatherington³

et al. 2008

Geosphere

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“…In the southeasternmost exposed Piedmont, the Pine Mountain internal basement massif (Figs. 1A, 2) includes Grenville basement rocks and a metasedimentary cover sequence of passive-margin quartzite and marble (Steltenpohl, 1992). Thomas, 1991Thomas, , 1993; abbreviations: T.P.=Texas promontory, T.E.=Tennessee embayment, V.P.=Virginia promontory.…”

Section: Southern Appalachian Alleghanian Orogenymentioning

confidence: 99%

Genetic relationship of rift-stage crustal structure, terrane accretion, and foreland tectonics along the southern Appalachian-Ouachita orogen

Thomas

2004

Journal of Geodynamics

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“…East-northeast-trending linear anomalies marking an unnamed splay of the Towaliga fault (Sears et al, 1981;Steltenpohl, 1992).…”

Section: (A)mentioning

confidence: 98%

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et al. 2013

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We dedicate this paper to the memory of coauthor Isidore (Izzy) Zietz, who died at age 93 while this paper was in review. After contributing to the early theoretical foundation for analysis of airborne magnetic surveys, Izzy became a leading advocate for aeromagnetic survey acquisition and interpretation throughout the U.S., combining surveys into regional, state, and national maps, and working with regional geologists in interpreting geophysical anomalies. Like many geologists, we have been energized by Izzy's contagious enthusiasm for using magnetic and gravity anomalies to delineate and characterize major tectonic features. Lessons from working with him on data from Alabama and elsewhere over the years will continue to infl uence our appreciation and understanding of aeromagnetic and gravity anomalies for interpreting the Earth's upper crust."Magnetics is never good, and gravity is even worse!" "…all of it can just be dashed." -Isidore Zietz ABSTRACT Aeromagnetic and gravity data sets obtained for Alabama (United States) have been digitally merged and fi ltered to enhance upper-crustal anomalies. Beneath the Appalachian Basin in northwestern Alabama, broad deep-crustal anomalies of the continental interior include the Grenville front and New York-Alabama lineament (dextral fault). Toward the east and south, high-angle discordance between the northeast-trending Appalachians and the east-west-trending wedge of overlapping Mesozoic and Cenozoic Gulf Coastal Plain sediments reveals how bedrock geophysical signatures progressively change with deeper burial. Highfrequency magnetic anomalies in the Appalachian deformed domain (ADD) correspond to amphibolites and mylonites outlining terranes, while broader, lower-amplitude domains include Paleozoic intrusive bodies and Grenville basement gneiss. Fundamental ADD structures (e.g., the Alexander City, Towaliga, and Goat Rock-Bartletts Ferry faults) can be traced southward beneath the Gulf Coastal Plain to the suture with Gondwanan crust of the Suwannee terrane. Within the ADD, there is clear magnetic distinction between Laurentian crust and the strongly linear, high-frequency magnetic highs of peri-Gondwanan (Carolina-Uchee) arc terranes. The contact (Central Piedmont suture) corresponds to surface exposures of the Bartletts Ferry fault. ADD magnetic and gravity signatures are truncated by the eastwest-trending Altamaha magnetic low associated with the Suwannee suture. Arcuate northeast-trending magnetic linears of the Suwannee terrane refl ect internal structure and Mesozoic failed-rift trends. Geophysical data can be used to make inferences on surface and subsurface geology and vice versa, which has applicability anywhere that bedrock is exposed or concealed beneath essentially non-magnetic sedimentary cover.

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The Pine Mountain window of Alabama: Basement-cover evolution in the southernmost exposed Appalachians

Cited by 7 publications

References 20 publications

Gondwanan/peri-Gondwanan origin for the Uchee terrane, Alabama and Georgia: Carolina zone or Suwannee terrane(?) and its suture with Grenvillian basement of the Pine Mountain window

Gondwanan/peri-Gondwanan origin for the Uchee terrane, Alabama and Georgia: Carolina zone or Suwannee terrane(?) and its suture with Grenvillian basement of the Pine Mountain window

Genetic relationship of rift-stage crustal structure, terrane accretion, and foreland tectonics along the southern Appalachian-Ouachita orogen

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