New occurrence of <i>Periastron reticulatum</i> Unger emend. Beck, an enigmatic Mississippian fossil plant

Gastaldo, Robert A.

doi:10.1017/s0022336000034715

Cited by 7 publications

(5 citation statements)

References 6 publications

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“…385-374 Ma) based on a well-documented marine invertebrate assemblage (Butts, 1926;Tull, 2002), the age of the uppermost JEC interval is not as well constrained. The uppermost Erin contains Veryhachium, a marine acritarch found in Devonian and older rocks in eastern North America, but which is very rare worldwide in the Carboniferous , and Periastron reticulatum (Unger, 1856;Scott and Jeffrey, 1914;Read and Campbell, 1939;Beck, 1978;Gastaldo, 1995), a rare and unusual aquatic or semi-aquatic plant ranging from Late Devonian (Fammenian) to Early Mississippian (Tournaisian), ca. 375-345 Ma.…”

Section: Time Of Emplacement Of the Metavolcanic Complexmentioning

confidence: 99%

“…In the Talladega belt, the Hillabee Greenstone structurally overlies fossiliferous, shallow-marine, Devonian to earliest Mississippian(?) rocks at the top of the Talladega Group, which represents the region's most outboard Laurentian margin cover sequence (Butts, 1926;Tull, 1982Tull, , 2002Tull et al, 1988;Gastaldo, 1995). Fossils, an internal unconformity, and abundant primary structures indicate that the Talladega Group and underlying units (Fig.…”

Section: Introductionmentioning

confidence: 99%

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Volcanic arc emplacement onto the southernmost Appalachian Laurentian shelf: Characteristics and constraints

Tull

Barineau

Mueller

et al. 2007

Geological Society of America Bulletin

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In the southernmost Appalachians, the Hillabee Greenstone, an Ordovician volcanic arc fragment, lies directly atop the outermost Laurentian Devonian-earliest Mississippian(?) shelf sequence at the structural top of the greenschist facies Talladega belt, the frontal metamorphic allochthon along this orogenic segment. The Hillabee Greenstone was emplaced between latest Devonian and middle Mississippian time. It and the uppermost Laurentian section were later repeated together within a series of map-scale imbricate slices of a postmetamorphic, dextral, transpressional, Alleghanian thrust duplex system that placed the high-grade eastern Blue Ridge allochthon atop the Talladega belt. Geochemical and geochronologic (U-Pb zircon) studies indicate that the Hillabee Greenstone's interstratifi ed tholeiitic metabasalt and calc-alkaline metadacite/rhyolite formed within an extensional setting on continental crust ca. 460-470 Ma. Palinspastic reconstructions of the southern Appalachian Ordovician margin place the Hillabee Greenstone outboard of the present position of the Pine Mountain terrane and suggest links to Ordovician plutonism in the overlying eastern Blue Ridge, and possibly to widespread K-bentonite deposits within Ordovician platform units. The tectonic evolution of the Hillabee Greenstone exhibits many unusual and intriguing features, including: (1) premetamorphic emplacement along a basal cryptic thrust, which is remarkably concordant to both hanging wall and footwall sequences across its entire extent (>230 km), (2) forma-tion, transport, and emplacement of the arc fragment accompanied by minimal deformation of the Hillabee Greenstone and underlying outer-margin shelf rocks, (3) emplacement temporally coincident with the adjacent collision of the younger, tectonically independent Ouachita volcanic arc with southeastern Laurentia. These features highlight strong contrasts in the Ordovician-Taconian evolution of the southern and northern parts of the Appalachian orogen.

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Section: Time Of Emplacement Of the Metavolcanic Complexmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Volcanic arc emplacement onto the southernmost Appalachian Laurentian shelf: Characteristics and constraints

Tull

Barineau

Mueller

et al. 2007

Geological Society of America Bulletin

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“…For details of the geometry of this deformation the reader is referred to Groszos (1996), Li (1996), Li and Tull (1998), and Palmes (1998). This early ductile deformation was most likely associated with the Acadian or earliest Alleghanian Orogenies because regionally it affected rocks at least as young as Silurian-Devonian, and possibly earliest Mississippian (Gastaldo, 1995;Unrug et al, 2000;Tull, 2002). In signifi cant contrast to the Blue Ridge, southwest of the CTZ, the Talladega stratigraphy is not deformed into isoclinal fold nappes, consisting instead predominantly of a thick, upright panel of low metamorphic grade Paleozoic stratigraphy (Fig.…”

Section: Figure 8 Northwest-southeast Cross Sections Across the Fronmentioning

confidence: 99%

“…It is overlain by resistant quartzites (Butting Ram/Cheaha Quartzite and overlying siliceous rocks of the Early Devonian-earliest Mississippian (?) Jemison Chert/Erin Slate; Butts, 1926;Gastaldo, 1995;Tull, 2002) (Fig. 3A).…”

Section: Southwest Correlationmentioning

confidence: 99%

Structural evolution of a major Appalachian salient-recess junction: Consequences of oblique collisional convergence across a continental margin transform fault

Tull¹,

Holm²

2005

Geol Soc America Bull

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Most orogenic belts exhibit broadly arcuate regional map-view trends of structural patterns. Commonly, the infl ection between opposing curves (recesses and salients) is a transverse zone marking a linear array of along-strike contrasts in regional structure and stratigraphy. Analysis of such transverse zones can provide insight into the processes affecting orogenic curvature. Curvature is especially distinctive along the west fl ank of the Appalachians, where the tightest salient/recess juncture is a thinned-skinned transverse zone in Georgia, separating the Alabama recess and Tennessee salient, and extending entirely across the width of deformed Laurentian cover rocks. This zone's most notable feature is a large oblique hanging-wall ramp within the frontal metamorphic allochthon formed during Alleghanian collisional events. The basal décollement steps several kilometers stratigraphically upward across this ramp from Proterozoic basement and its overlying Late Proterozoic rift sequence (Tennessee salient), southwestward into basal Cambrian and younger rocks (Alabama recess). This ramp resulted from oblique sinistral displacement of the allochthon against an earlier, eastfacing, dextral continental margin transform fault that initially separated adjacent rifted margins of opposite polarity. Differences in the distribution, thickness, and facies of units indicate that important variations in basin geometry existed across the curvature infl ection before Paleozoic deformation, suggesting that the orogenic curvature in part results from an inherited basin architecture. Translation of the allochthon over the ramp caused defl ection of the tectonic transport trajectory, major cross folding, and rotation of earlier structures. Associated out-of-plane deformation propagated outward across the foreland, producing the array of thinnedskinned transverse structures aligned into the transverse zone.

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“…Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions P aleozoic plant fossils with structurally preserved tissues are rare in Alabama. Stems and cones of Mississippian age have been recovered from the Erin Shale in Clay County (Adams et al 1926;Gastaldo 1995;Gastaldo, Guthrie, and Steltonpohl 1993). The Erin Shale fossils are preserved in a carbonaceous shale as mixed quartz and apatite nodules that contain carbonized plant cellular material.…”

mentioning

confidence: 99%

Structurally Preserved Paleozoic Plant Fossils: from the Cahaba Coal Field Jefferson County, Alabama

Barwood

2007

Rocks & Minerals

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New occurrence of Periastron reticulatum Unger emend. Beck, an enigmatic Mississippian fossil plant

Cited by 7 publications

References 6 publications

Volcanic arc emplacement onto the southernmost Appalachian Laurentian shelf: Characteristics and constraints

Volcanic arc emplacement onto the southernmost Appalachian Laurentian shelf: Characteristics and constraints

Structural evolution of a major Appalachian salient-recess junction: Consequences of oblique collisional convergence across a continental margin transform fault

Structurally Preserved Paleozoic Plant Fossils: from the Cahaba Coal Field Jefferson County, Alabama

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