Abstract The allochthonous Talladega belt of eastern-northeastern Alabama and northwestern Georgia is a northeast striking, fault bounded block of lower greenschist facies metasedimentary and metaigneous rocks that formed along the margin of Laurentia at or outboard of the seaward edge of the Alabama promontory. Bounded by metamorphic rocks of the higher grade Neoproterozoic(?) to Carboniferous eastern Blue Ridge on the southeast and unmetamorphosed to anchimetamorphic Paleozoic rocks of the Appalachian foreland on the northwest, the Talladega belt includes shelf facies rocks of the latest Neoproterozoic/earliest Cambrian Kahatchee Mountain Group, Cambrian-Ordovician Sylacauga Marble Group, and the latest Silurian(?) to uppermost Devonian/earliest Mississippian Talladega Group. Along the southeastern flank of these metasedimentary sequences, a Middle Ordovician back-arc terrane (Hillabee Greenstone) was tectonically emplaced along a cryptic pre-metamorphic thrust fault (Hillabee thrust) and subsequently dismembered with units of the upper Talladega Group along the post-metamorphic Hollins Line fault system. Importantly, strata within the Talladega belt are critical for understanding the tectonic evolution of the southern Appalachian orogen when coupled with the geologic history of adjacent terranes. Rocks of the lower Talladega Group, the Lay Dam Formation, suggest latest Silurian–earliest Devonian tectonism that is only now being recognized in other areas of the southern Appalachians. Additionally, correlation between the Middle Ordovician Hillabee Greenstone and similar bimodal metavolcanic suites in the Alabama eastern Blue Ridge and equivalent Dahlonega Gold belt of Georgia and North Carolina suggests the presence of an extensive back-arc volcanic system on the Laurentian plate just outboard of the continental margin during the Ordovician and has significant implications for models of southern Appalachian Taconic orogenesis.

The Talladega slate belt in eastern Alabama represents a crystalline thrust sheet composed of low-grade metasediments. Three major lithologic sequences comprise the Talladega slate belt: (1) the Kahatchee Mountain Group, (2) the Sylacauga Marble Group, and (3) the Talladega Group. The contact relationships between the Sylacauga Marble Group and the Talladega Group indicate that the phyllites and slates of the Talladega Group rest unconformably on marbles of the Sylacauga Marble Group. Previous workers have identified specific stratigraphic sequences within the Talladega Group both in the north-central portion of the Talladega slate belt and in the southern portion of the belt. Little work has been carried out in the south-central portion of the Talladega slate belt, a region intermediate between areas to the northeast and southwest where the regional stratigraphy has been defined. To the northwest in Cleburne and Clay Counties, Alabama, the Talladega Group has been broken down into the Heflin Phyllite, the Able Gap Formation, and the Chulafinnee Schist. To the southwest in Chilton County, Alabama, similar units have been mapped as the Lay Dam Formation, the Butting Ram Sandstone, and the Jemison Chert. These units have not been mapped through this intermediate south-central region of the Talladega slate belt because of the absence by faulting of a major sandstone unit, the Cheaha Quartzite, which has been used for regional correlation. Another prominent unit, the Jemison Chert, which outcrops to the southeast of the Cheaha Quartzite, continues across this region and was used to correlate the regional stratigraphy from the northeast with that in the southwest. Detailed mapping has shown that a small slice of paper-thin quartzites of the Jemison Chert interval has overridden the Cheaha Quartzite. The geometric relationships between these two units, the differing petrologic character of these ridge-forming lithologies, the duplication of the Jemison Chert interval, and the emplacement of this imbricate slice of Jemison, in addition to structural fabric data, suggest that this termination of the Cheaha Quartzite is fault related.

The Talladega belt in Alabama and Georgia is the northwesternmost belt of the Appalachian Piedmont metamorphic province. It contains low-rank metasediments and metavolcanics that have been thrust faulted onto Paleozoic sediments of the Valley and Ridge province via the Cartersville-Talladega fault system. The age of several formations in the southwestern part of the Talladega belt in Alabama has been determined to be Devonian, but controversy exists concerning the age of much of the rest of the belt. Another major problem has been the age and structure relationships of the Talladega belt to the Precambrian and Lower Cambrian rocks of the Blue Ridge province on strike with the Talladega belt to the northeast. In the Borden Springs area, Cleburne County, Alabama, nappes of the Lower Cambrian Weisner and Shady Formations rest on younger Paleozoic rocks immediately northwest of the Talladega belt. A sequence composed mainly of slates and quartzites characterized by graded beds lies between the Talladega belt and the nappes of Weisner and Shady. Distinctive lithologies within this sequence are found also within the Talladega belt near Borden Springs and also near the southwest end of the belt in Alabama within metasediments immediately below the Jumbo Dolomite of the Sylacauga Marble Group. Although the slate-quartzite sequence has been interpreted in recent years as being Ordovician to Devonian, detailed mapping in the Borden Springs area indicates that it is correlative with the Early Cambrian Weisner and Shady, although somewhat different in sedimentary aspect from Weisner and Shady in nappes to the west. Therefore, the Talladega belt may contain rocks at least as old as Early Cambrian and may be at least partly equivalent in age to rocks of the Blue Ridge province. The slate-quartzite sequence lies northwest, west, and southeast of an anticlinal region of younger Paleozoic sediments in western Georgia, over which it was thrust faulted. It thus forms an imbricated nappe sequence rooted, if at all, beneath the Piedmont province to the southeast.

A major carbonate sequence occurs within the lower part of the Talladega slate belt in Chilton, Coosa, and Talladega Counties. The carbonate units are overlain by a major regional unconformity known as the pre-Lay Dam Formation unconformity. The carbonate sequence below the unconformity is represented in different areas by the Jumbo Dolomite, the Marble Valley carbonates, and the Sylacauga marbles. At the type location in Chilton County, the Jumbo is a 67-m-thick, predominantly thickly bedded dolostone. The contact with the underlying slates of the Wash Creek Slate (Mount Zion Formation) is an interlayered zone of dolostone and fine, commonly graphitic, clastic rock. This zone grades upward into a dolostone that contains a few pelitic layers. Near the base, the Jumbo contains intraclasts and recrystallized fragments up to 6 cm in length. Rounded quartz grains are disseminated in the lower section of the Jumbo. Near the middle of the massively bedded dolostone is a layer that contains intraclasts of massive and laminated carbonate as much as 12 cm in length. Just below the unconformity in the type section, the upper part of the Jumbo contains laminations of fine-grained clastic rock. Along strike to the northeast and southwest the unconformity appears to have erosional relief. Less than 1 km west of the type location the unconformity truncates the carbonate sequence completely. To the northeast the pre-Lay Dam Formation unconformity appears to rise in the section in the Marble Valley carbonates and the Sylacauga marbles, exposing a very thick carbonate sequence. Stratigraphic and structural relationships of the Jumbo, Marble Valley, and Sylacauga marbles are not yet resolved. Initial data indicate that the Jumbo occurs stratigraphically below and to the northwest of the Marble Valley carbonates, suggesting that the Jumbo is the oldest carbonate unit in the sequence.

Abstract Independent researchers working in the Talladega belt, Ashland-Wedowee-Emuckfaw belt, and Opelika Complex of Alabama, as well as the Dahlonega gold belt and western Inner Piedmont of Alabama, Georgia, and the Carolinas, have mapped stratigraphic sequences unique to each region. Although historically considered distinct terranes of disparate origin, a synthesis of data suggests that each includes lithologic units that formed in an Ordovician back-arc basin (Wedowee-Emuckfaw-Dahlonega basin—WEDB). Rocks in these terranes include varying proportions of metamorphosed mafic and bimodal volcanic rock suites interlayered with deep-water metasedimentary rock sequences. Metavolcanic rocks yield ages that are Early–Middle Ordovician (480–460 Ma) and interlayered metasedimentary units are populated with both Grenville and Early–Middle Ordovician detrital zircons. Metamafic rocks display geochemical trends ranging from mid-oceanic-ridge basalt to arc affinity, similar to modern back-arc basalts. The collective data set limits formation of the WEDB to a suprasubduction system built on and adjacent to upper Neoproterozoic–lower Paleozoic rocks of the passive Laurentian margin at the trailing edge of Iapetus, specifically in a continental margin back-arc setting. Overwhelmingly, the geologic history of the southern Appalachians, including rocks of the WEDB described here, indicates that the Ordovician Taconic orogeny in the southern Appalachians developed in an accretionary orogenic setting instead of the traditional collisional orogenic setting attributed to subduction of the Laurentian margin beneath an exotic or peri-Laurentian arc. Well-studied Cenozoic accretionary orogens provide excellent analogs for Taconic orogenesis, and an accretionary orogenic model for the southern Appalachian Taconic orogeny can account for aspects of Ordovician tectonics not easily explained through collisional orogenesis.

ABSTRACT The Brevard fault zone is one of the largest faults in the Appalachians, extending from Alabama to Virginia. It had a very complex history of movement and reactivation, with three movement episodes: (1) Acadian-Neoacadian (403–345 Ma) movement accompanying the thermal peak of metamorphism and deformation with dextral, southwest-directed emplacement of the Inner Piedmont; (2) ductile dextral reactivation during the early Alleghanian (~280 Ma) under lower-greenschist-facies conditions; and (3) brittle dip-slip reactivation during the late Alleghanian (260 Ma?). The Brevard is comparable to other large faults with polyphase movement in other orogens worldwide, for example, the Periadriatic line in the Alps. Two types of far-traveled, fault-bounded horses have been identified in the Brevard fault zone in the Carolinas: (1) metasedimentary and granitoid horses located along the southeastern margin of the Alleghanian retrogressive ductile dextral Brevard fault zone in North and South Carolina; and (2) limestone/dolostone horses located along the brittle, late Alleghanian Rosman thrust, the contact between Blue Ridge and Brevard fault zone rocks in North and South Carolina. Field, stratigraphic, petrographic, and Sr-isotope data suggest the carbonate horses may be derived from Valley and Ridge carbonates in the Blue Ridge–Piedmont megathrust sheet footwall. The horses of metasedimentary and granitoid rocks occur along faults that cut klippen of the southwest-directed Inner Piedmont Acadian-Neoacadian Alto (Six Mile) allochthon. New laser ablation– inductively coupled plasma–mass spectrometry (LA-ICP-MS) U-Pb zircon analyses from the metasedimentary mylonite component yield a detrital zircon suite dominated by 600 and 500 Ma zircons, and a second zircon population ranging from 2100 to 1300 Ma, with essentially no Grenvillian zircons, suggesting a peri-Gondwanan provenance. The granitoid component has a sensitive high-resolution ion microprobe (SHRIMP) age of 421 ± 14 Ma, similar to the ~430 Ma plutonic suite in northern Virginia and Maryland—a prominent component of the Cat Square terrane detrital zircon suite in the Carolinas. Peri-Gondwanan Neoproterozoic to Cambrian Avalon–Carolina superterrane rocks are nowhere in contact with the Brevard fault zone at present erosion level. While these far-traveled metasedimentary and granitoid horses may have originated several hundred kilometers farther northeast in the central Appalachians, they could alternatively be remnants of Avalon–Carolina superterrane rocks that once formed the tectonic lid of the southwest-directed Neoacadian–early Alleghanian (Late Devonian–early Mississippian) orogenic channel formed during north-to-south zippered accretion of Avalon–Carolina. The remnant fossil subduction zone survives as the central Piedmont suture. Avalon–Carolina terrane rocks would have once covered the Inner Piedmont (and easternmost Blue Ridge) to depths of >20 km, and have since been eroded. Data from these two suites of horses provide additional insights into the mid- to late Paleozoic history and kinematics of the Brevard fault zone, Inner Piedmont, and Avalon–Carolina superterrane. It was six men of Indostan To learning much inclined, Who went to see the Elephant (Though all of them were blind), That each by observation Might satisfy his mind. … And so these men of Indostan Disputed loud and long, Each in his own opinion Exceeding stiff and strong, Though each was partly in the right, And all were in the wrong. —John Godfrey Saxe (1816–1887) “The Blind Men and the Elephant”

ABSTRACT The city of Youngstown, the county seat of Mahoning County, is situated along the Mahoning River in northeastern Ohio, USA. Its early industrial growth was due to the ready availability of iron ore, limestone, abundant forests, and coal, all used for production of iron and then steel during the last two centuries. Local Massillon sandstone and Vanport limestone from Ohio and western Pennsylvania were used to construct mansions and other structures in the nineteenth century. By the early 1900s, other stones including Berea sandstone from Ohio, and sedimentary, metamorphic, and intrusive igneous stones quarried at other sites in North America and Europe, were being utilized as dimension stone in Youngstown. This guide briefly reviews the geological and cultural setting of Youngstown, and describes the building, decorative, and monumental stones used for a variety of structures in downtown Youngstown, with emphasis on stone used for the exterior and interior of major structures. Sites include the Butler Institute of American Art, which is clad with marble and incorporates an assortment of other stone inside and outside of the complex, and St. Columba Cathedral, whose limestone is known commercially as Mankato ( Kasota ) stone and is full of fossil burrows, as well as a sampling of stones used in beautiful Oak Hill Cemetery.