Conodont Sequence Research Articles

Famennian conodont assemblage in the Compte section (Upper Devonian, Central Pyrenees) and its comparison with Eurasian sequences

A detailed study of the fossil assemblages of Famennian conodonts has been carried out in the Compte section in the Central Pyrenees. The studied section comprises the upper part of the Comabella Formation, the La Mena Fm and the lower part of the Barousse Fm. Fifty samples have been collected from a 11.73 m thick Famennian stratigraphic succession. Forty–seven lower–middle Famennian conodont taxa have been identified, belonging to four genera: Palmatolepis, Polygnathus, Icriodus and Mehlina. The identified conodont assemblages change through the studied section: in the lower part, Palmatolepis and Icriodus taxa are more frequent and in the overlaying strata, Palmatolepis and Polygnathus taxa are dominant. Several conodont taxa have been recorded for the first time in Central Pyrenees zone. The conodont sequence analysis suggests a lower to middle Famennian age (from the termini to mg. marginifera Zones) in the Compte section (Beds 98–120). On the other hand, a comparison of the Pyrenean conodont assemblages with those from other relevant regions has been carried out. The conodont associations from Compte shows certain similarities with those from western and eastern Europe; however, sequences from eastern and central Asian exhibit some differences.

Lower Triassic conodont biostratigraphy of the Guryul Ravine section, Kashmir

The Guryul Ravine section in Kashmir, northern India is an important reference section for global Lower Triassic stratigraphy. Once a candidate Global Stratotype Section and Point (GSSP) for the Permian-Triassic Boundary (PTB), the section has attracted intense attention for the PTB beds, but few studies have concerned the entire Lower Triassic stratigraphy. As one of the most continuous marine Lower Triassic successions on the northern margins of Gondwana, the Guryul Ravine section provides an important conodont biostratigraphic yardstick for worldwide correlations. This study presents recent results of the Lower Triassic conodont zonation from the Guryul Ravine section. A total of 6500 elements including 1600 P1 elements were recovered. Ten conodont zones were recognized from the Griesbachian to Spathian: Hindeodus parvus, Isarcicella staeschei, Clarkina planata, Neoclarkina krystyni, Neospathodus dieneri, Ns. pakistanensis, Novispathodus waageni, Scythogondolella mosheri, Nv. pingdingshanensis, and Nv. abruptus – Nv. brevissimus zones. The PTB is placed within Bed 52 in Unit E2, 80 cm above the base of Unit E2, based on the first occurrence (FO) of H. parvus. The Induan–Olenekian boundary (IOB) is tentatively placed at the base of Member G according to the positive maximum δ13Ccarb values, but it could be slightly higher based on conodonts. The Smithian-Spathian boundary (SSB) is drawn at the top of Member H based on the FO of Nv. pingdingshanensis and the carbon mdpt(N3-P3). Several conodont taxa are newly recognized near the top of the study section where the conodont fauna is dominated by segminiplanate elements of the Neogondolellinae. Many of these age-diagnostic species have been identified in other sections around the world, and their occurrence in Guryul Ravine supports their potential for worldwide correlation. The conodont sequence erected from the study section corresponds well to those of South China (e.g. Meishan) and elsewhere worldwide. The newly established conodont zonation from Kashmir provides a high precision time-frame to consider biotic evolution and environmental change during the Early Triassic, a crucial period of Earth history.

Upper Eifelian and Givetian (Middle Devonian) conodont sequence at Renanué (Aragonian Pyrenees, Spain): a relevant section for Givetian Chronostratigraphy

ABSTRACT The study of 111 conodont samples has provided the first detailed biostratigraphical subdivision of the Renanué section ranging from the upper Eifelian ensensis Zone into the uppermost Givetian norrisi Zone. The conodont record supports the global threefold subdivision of the Givetian. The lower boundary of the Lower Givetian coincides with the lower boundary of the Givetian and is recognised in the uppermost 5 cm of Bed −8 with the entry of Polygnathus hemiansatus. The lower boundary of the Middle Givetian is identified in Bed 5 with the joint entry of P. varcus and P. rhenanus. Lack of Schmidtognathus precludes identification of the Upper Givetian lower boundary, but the conodont assemblage suggests its position around the lower part of Bed 55. Absence of Ancyrodella and other key taxa impeded precise identification of the Frasnian lower boundary and its earliest zones. Our lowest record of P. webbi seconds its global downwards range extension into the Upper Givetian. The uppermost local record of P. rhenanus might sustain the upward extension of its range into the latifossatus Zone.

A gap in sedimentation in the Silurian section of the Subpolar Urals at the Ludlow-Pridoli boundary

Research subject.The article discusses the results of a new detailed study of a reference section of the Upper Silurian in the Subpolar Urals. This study was undertaken to clarify the existing contradictions concerning the age of the Ludlow-Pridoli boundary deposits and the definition of the Ludlow-Pridoli boundary, which is based on the study of different fauna groups.Materials and methods.The newly collected collections contained more than 100 samples of sedimentary rocks with fossil macro fauna, 22 tests on microfauna, 198 tests on chemical analysis for determining the content of Ba, Sr and δ13C and δ18O isotopes in carbonates. The results of experiments were confirmed by the authors’ bio-sedimentological, paleo-ecological and chemostratigraphic data.Results.The conducted research confirmed the existence of a gap in sedimentation at the end of Ludlow; clarified the thickness of the Sizim stage in the reference section; elucidated its sedimentological and chemostratigraphic characteristics; allowed changes in biodiversity due to a change in the sedimentation regime, paleoecological impact on biota in the late Ludlow and restoration of biota in the early Pridoli to be traced. The study also demonstrated that the time boundaries of the transgressive and regressive stages in the development of the Northern Ural sea basin and the event-stratigraphic boundary of the Ludlow-Pridoli were directly related to the main global events in the Late Silurian (Lau Event, Lower Pridolian Event), the traces of which are preserved in the studied section.Conclusions.The intensification of regressive tendencies across the largest part of the Northern Ural paleobasin in the Late Ludlow, widespread development of microbial biota, cessation of the Silurian reef formation, as well as the extinction of Pentamerida brachiopods – exclusively, indicate a significant ecosystematic restructuring in the late Ludlow. It can be assumed that the absence of a significant positive deviation of the δ13C global Lau Event in this section is associated with the identified gap, the amplitude of which correlates with the Ozarkodina snajdri and Ozarkodina crispa zones located above the Polygnathoides siluricus zone in the conodont sequence of the Upper Ludlow.

New Data on the Age of the Yukiang (Yujiang) Formation at Liujing, Guangxi, South China

AbstractThe age of the Yukiang (Yujiang) Formation has been shrouded in controversy for more than 75 years. New investigation at the Liujing section, Hengxian County, Guangxi, has revealed a conodont sequence assignable to two Early Devonian conodont zonations: the Eognathodus kindlei?–Polygnathus pireneae Zone and the Polygnathus nothoperbonus Zone from oldest to youngest. The Gaoling and Mahuangling members of the Nahkaoling (Nagaoling) Formation and the overlying Xiayiling Member and lower part of the Shizhou Member of the Yukiang Formation are proven to belong to the Pragian Eognathodus kindlei?–Polygnathus pireneae Zone. The co‐occurrence of Polygnathus pireneae and Pol. sokolovi in the lower part of the Shizhou Member demonstrates that this interval can be approximately correlated with the uppermost part of the Polygnathus pireneae Zone. However, precise level identification of the Pragian–Emsian Boundary (PEB) in the Liujing section remains dfficult due to the scarcity of suitable limestone samples for conodont analysis from the middle and upper parts of the Shizhou Member. The Daliancun and Liujing members of the Yukiang Formation and the lower part of the overlying Moding Formation are assigned to the Polygnathus nothoperbonus Zone with the nominal species of this biozone ranging from the bottom of the Daliancun Member to the lower part of the Moding Formation.

Conodont characteristic of the Lochkovian-Pragian boundary interval in the Mindigulovo section (western slope of the Southern Urals)

Conodonts from the Sherlubay (upper Lochkovian) and Kulamat (lower Pragian) Horizons of the Mindigulovo section (western slope of the Southern Urals) were studied in detail. The conodont sequence can be globally correlated. The sequence contains important cosmopolitan taxa. The taxon index of the global zone gilberti was discovered at the top of the Sherlubay Horizon. Overlying Kulamat Horizon in the lower Pragian is characterised by the proliferation of typical species of the irregularis Zone in addition to the taxon index. Almost all characteristic Lochkovian species completely disappear. The observed successive morphological changes in Masaraella pandora: Mas. pandora morphotype alpha → Mas. pandora morphotype beta → Mas. pandora cf. morphotype zeta and Eognathodus: Eognathodus cf. irregularis → Gondwania cf. profunda are close to the development of Masaraella pandora → Eognathodus phyletic lineage, proposed by Murphy (2005). In the revealed evolutionary lineage of Mas. pandora–Eognathodus, the starting of eognathodontid from Mas. pandora is a biostratigraphical criterion for the establishment of the Lohkovian/Pragian boundary, along with lithological and macrofaunal control. Together with the deep-sea eognatodontid fauna, another index taxa as Caudicriodus steinachensis morphotype eta and Pelekysgnathus cf. serratus brunsvicensis of the alternative scale (Slavik 2004; Slavik et al. 2007) were recorded. The parallel presence of shallow-water icriodontid and deep-water eognathodontid biofacies at the lower part of Kulamat Horizon of the Pragian sediments in the Southern Urals is relevant for interregional correlations.

Cisuralian–Guadalupian conodont sequence from the Shaiwa section, Ziyun, Guizhou, South China

A sequence of successive conodont datums and zones for the Cisuralian and Guadalupian series for the South China region of the Equatorial Warm Water Province is proposed based on the Shaiwa section, Ziyun, Guizhou. The seven conodont zones in ascending order are: Sweetognathus aff. whitei Zone of Artinskian Stage, a set of three new Kungurian zones of Sweetognathus guizhouensis Zone, Sweetognathus subsymmetricus Zone, Mesogondolella nashuiensis Zone; the Mesogondolella idahoensis lamberti Zone of uppermost Kungurian, the Guadalupian zones of Jinogondolella aserrata followed by Jinogondolella postserrata. The base of the Kungurian Stage is tentatively defined by the first occurrence of S. guizhouensis, 174.5m above the base of the Sidazhai Formation. This suite of conodont datums and zones will help to improve the global correlations of Permian strata of the Kungurian Stage.

Graphic correlation of the upper Eifelian to lower Frasnian (Middle-Upper Devonian) conodont sequences in the Spanish Central Pyrenees and comparison with composite standards from other areas

Graphic correlation of the upper Eifelian to lower Frasnian (Middle-Upper Devonian) conodont sequences in the Spanish Central Pyrenees and comparison with composite standards from other areas

The middle and upper Lochkovian (Lower Devonian) conodont successions in key peri‐Gondwana localities (Spanish Central Pyrenees and Prague Synform) and their relevance for global correlations

AbstractDetailed correlation, based on conodont sequences, between middle and upper Lochkovian carbonate successions from two key peri‐Gondwanan regions, the Spanish Central Pyrenees and the Prague Synform, is attained for the first time. This correlation facilitates the definition of tie points for further multidisciplinary studies that seek to establish high‐resolution temporal subdivision and global correlation. Some intervals have a precision of less than 0.5 Ma, which is significantly greater than in previous studies. The estimated elapsed time considered herein is about 3.2 Ma and is subdivided into five major zones of global scope: transitans‐trigonicus, trigonicus‐kutscheri, kutscheri‐pandora β, pandora β‐gilberti and gilberti‐steinachensis β. By providing tie points and globally applicable criteria, this research contributes to the international cooperative effort to subdivide the Devonian standard stages into globally recognised substages.

The Middle and Upper Devonian conodont sequence from La Guardia D’Àres Sections (Spanish Central Pyrenees)

The Middle and Upper Devonian conodont sequence from La Guardia D’Àres Sections (Spanish Central Pyrenees)

Upper Givetian and Frasnian (Middle and Upper Devonian) conodonts from Ampriú (Aragonian Pyrenees, Spain): global correlations and palaeogeographic relations

Abstract: This report describes for the first time a part of the Middle and Upper Devonian conodont sequence of the Sierra Negra Subfacies in the Aragonian Pyrenees (Spain), establishing the basis for further sound correlations both across the distinct Pyrenean facies and subfacies and on other relevant world areas. The description of 20 conodont taxa and their stratigraphical distribution permits recognition of two separate time intervals. The older one corresponds to the lower Upper Givetian (Middle Devonian), hermanni to cristatus ectypus zones. The younger interval is uppermost Lower Frasnian to lower Middle Frasnian (Upper Devonian) and is equivalent to MN4–MN6 zones. The combination of litho‐ and conodont biofacies supports the distinction between the Sierra Negra and Renanué Subfacies. Conodont biofacies for the studied interval are partially close to the ones from the Compte Subfacies, but lithofacies are clearly different. This faunal similarity fosters accurate correlation between subfacies and stimulates further research aiming at Devonian Pyrenean basin(s) reconstruction. Additionally, this faunal sequence permits direct comparison with regions located in northern Gondwana and in the Russian platform for part of the interval. Comparison with Laurasia, mainly with the Northwest Territories of Canada and the north‐western United States, is also provided. Some taxa are also common with eastern and central Asia (China, Siberia, Tadzhikistan, Afghanistan), Australia and western USA (Nevada).

Conodont Evidence for the Age of the Panxian Fauna, Guizhou, China

Abstract: Detailed conodont analysis on the Yangjuan-Chupiwa section, Xinmin, Panxian County, Guizhou Province, revealed a conodont sequence including four Anisian conodont zones, viz. Nicoraella germanica Zone, Nc. kockeli Zone, Paragondolella bifurcata Zone and Neogondolella constricta Zone. These zones indicate that the upper Guanling Formation consists of strata from the Bithynian to the Illyrian of the Anisian. Appearance of Neogondolella constricta suggests that the Anisian/Ladinian boundary might be in the overlying Yangliujing Formation. The Panxian Fauna with well-preserved marine reptile and fish fossils is proved to belong to the lower part of the conodont Nc. kockeli Zone in the studied area. Thus, the age of the Panxian Fauna could be the early Pelsonian of the Anisian.

Lower Triassic conodont sequence in Chaohu, Anhui Province, China and its global correlation

The Early Triassic paleogeographical setting of the Chaohu section in China was in a deep part of the Yangtze platform and this has resulted in a rather complete Lower Triassic sequence with rich ammonoid and conodont successions. Three Lower Triassic sections, West Pingdingshan, North Pingdingshan and South Majiashan, have been sampled in detail for a systematic conodont study. Eight conodont zones are recognized; in ascending order these are the zones of Hindeodus typicalis, Neogondolella krystyni, Neospathodus kummeli, Neospathodus dieneri, Neospathodus waageni, Neospathodus pingdingshanensis, Neospathodus homeri, and Neospathodus anhuinensis. These are correlated with the sequences in North America and other areas of the world. The succession provides a good basis for the definition of the global stratotype of the Induan–Olenekian boundary (GSSP), which has been proposed at the base of the Neospathodus waageni Zone in West Pingdingshan. Seven new species are introduced: Neospathodus chaohuensis, N. chii, N. concavus, N. eotriangularis, N. pingdingshanensis, N. posterolongatus, N. tongi, a new subspecies N. waageni eowaageni, and three morphotypes of N. dieneri.

SERPUKHOVIAN CONODONT SEQUENCE AND THE VISEAN- SERPUKHOVIAN BOUNDARY IN SOUTH CHINA

This paper describes in detail the conodont sequence of Upper Visean (equivalent to Tatangian of China), Serpukhovian (equivalent to Duwuan of China) and the base of Bashkirian (equivalent to Luosuan of China) in South China. The following conodont zones can be recognized in descending order: Declinognathodus noduliferus, Gnathodus bilineatus bollandensis, Lochriea cruciformis, L. ziegleri and L. nodosa zones. The first occurrences of Lochriea ziegleri and D. noduliferus (or D. lateralis ) are considered as the bases of Serpukhovian and Bashkirian, respectively. The correlation of the conodont sequence from Upper Visean to the base of Bashkirian between South China and the Moscow Basin, South Urals, Great Britain, Ireland and North America is discussed.

Upper Carboniferous (pennsylvanian) conodonts from South Guizhou of China

This paper describes in detail che conodont sequence of che Upper Carboniferous (Pennsylvanian) and the upper and lower boundaries in this interval at the Nashui section in Luodian, South Guizhou. The following 23 conodont zones, in descending order, can be recognized: Streptognathodus isolatus , S. wabaunsensis, S. tenuialveus, S. firmus, S. nashuiensis, S. simulator, S. guizhouensis, S. gracilis-S. excelsus, S. cancellosus, S. clavatulus, S. nodocarinatus, Idiognathodus podolskensis, Mesogondolella clarki-Idiognathodus robustus, Diplognathodus orphanus-D. ellesmerensis, ldiognathoides ouachitensis, Streptognathodus expansus, Idiognathoides sulcatus parvus, Neognathodus bassleri-Idiognathodus primulus, N. symmetricus-Idiognathodus primulus, N. symmetricus, Idiognathoides corrugatus-I. pacificus, I. sinuatus, I. sulcatus sulcatus and Declinognathodus noduliferus zones. The first occurrences of Streptognathodus isolatus and Declinognathodus noduliferus afe recognized at the bases of che Permian and the Upper Carboniferous (Pennsylvanian), respectively. The Upper Carboniferous (Pennsylvanian) conodont sequences are discussed and based on these conodont sequences, correlations between Upper Carboniferous (Pennsylvanian) Stages in Chinese and Russian sections, as well as North America are discussed. Additionally, eight new conodont species are also described in this paper.

CONODONT SEQUENCE BIOSTRATIGRAPHY OF THE HERMOSA GROUP (PENNSYLVANIAN) AT HONAKER TRAIL, PARADOX BASIN, UTAH

In cyclical Pennsylvanian strata, conodonts find their greatest stratigraphic utility as biotic signatures of physically defined stratigraphic entities (cycles, parasequences, high frequency sequences, etc.) rather then the primary means of stratigraphic subdivision (e.g., biostratigraphic interval zones). The practice of identifying depositional entities for purposes of regional correlation on the basis of their constituent conodont faunas is herein called conodont sequence biostratigraphy. In this paper, the concept is utilized to successfully correlate Pennsylvanian cycles of the Paradox basin with their Midcontinent counterparts.The Honaker Trail section is the most accessible and well-studied succession of carbonate shelf strata in the Paradox basin. Approximately 350 m of cyclically bedded limestone, sandstone, and shale comprising 53 fifth-order cycles are exposed along the cliffs of the deeply entrenched San Juan River. Maximum transgressive facies of 19 cycles yielded Idiognathodus-Neognathodus- and/or Streptognathodus-dominated conodont faunas. Those from the Chimney Rock, Gothic, LHT-5, UHT-3, UHT-5, UHT-8, unnamed limestone, and Shafer correspond to faunas from the Verdigris, Lower Fort Scott, Altamont (Lake Neosho), Lost Branch, Hertha (Mound City), Swope (Hushpuckney), Dennis (Stark), and South Bend cycles of the Midcontinent, respectively. By extrapolation, all minor cycles of the Marmaton, Pleasanton, and Bronson Groups (except for the Critzer) also appear to have counterparts at Honaker Trail.The position of the Desmoinesian–Missourian boundary in the Honaker Trail section can be approximated using conodonts in conjunction with fusulinids. The highest Desmoinesian conodont fauna, the Idiognathodus nodocarinatus fauna, occurs in cycle UHT-3 in the lower part of the Upper Honaker Trail sequence. The highest occurrence of Beedeina occurs in the same cycle. The lowest conodont fauna with the Missourian species I. eccentricus appears two cycles higher, in cycle UHT-5. Because in the Midcontinent region a small interval of strata separates the first appearance of I. eccentricus from the base of the Missourian, we place the base of the Missourian at the base of cycle UHT-4 (bed 105) at Honaker Trail. The appearance of Streptognathodus firmus and S. pawhuskaensis in the Shafer limestone indicates that the Missourian–Virgilian boundary lies slightly above or below this stratigraphic horizon.

Conodont sequence biostratigraphy of the Hermosa Group (Pennsylvanian) at Honaker Trail, Paradox Basin, Utah

In cyclical Pennsylvanian strata, conodonts find their greatest stratigraphic utility as biotic signatures of physically defined stratigraphic entities (cycles, parasequences, high frequency sequences, etc.) rather then the primary means of stratigraphic subdivision (e.g., biostratigraphic interval zones). The practice of identifying depositional entities for purposes of regional correlation on the basis of their constituent conodont faunas is herein called conodont sequence biostratigraphy. In this paper, the concept is utilized to successfully correlate Pennsylvanian cycles of the Paradox basin with their Midcontinent counterparts.The Honaker Trail section is the most accessible and well-studied succession of carbonate shelf strata in the Paradox basin. Approximately 350 m of cyclically bedded limestone, sandstone, and shale comprising 53 fifth-order cycles are exposed along the cliffs of the deeply entrenched San Juan River. Maximum transgressive facies of 19 cycles yielded Idiognathodus-Neognathodus- and/or Streptognathodus-dominated conodont faunas. Those from the Chimney Rock, Gothic, LHT-5, UHT-3, UHT-5, UHT-8, unnamed limestone, and Shafer correspond to faunas from the Verdigris, Lower Fort Scott, Altamont (Lake Neosho), Lost Branch, Hertha (Mound City), Swope (Hushpuckney), Dennis (Stark), and South Bend cycles of the Midcontinent, respectively. By extrapolation, all minor cycles of the Marmaton, Pleasanton, and Bronson Groups (except for the Critzer) also appear to have counterparts at Honaker Trail.The position of the Desmoinesian–Missourian boundary in the Honaker Trail section can be approximated using conodonts in conjunction with fusulinids. The highest Desmoinesian conodont fauna, the Idiognathodus nodocarinatus fauna, occurs in cycle UHT-3 in the lower part of the Upper Honaker Trail sequence. The highest occurrence of Beedeina occurs in the same cycle. The lowest conodont fauna with the Missourian species I. eccentricus appears two cycles higher, in cycle UHT-5. Because in the Midcontinent region a small interval of strata separates the first appearance of I. eccentricus from the base of the Missourian, we place the base of the Missourian at the base of cycle UHT-4 (bed 105) at Honaker Trail. The appearance of Streptognathodus firmus and S. pawhuskaensis in the Shafer limestone indicates that the Missourian–Virgilian boundary lies slightly above or below this stratigraphic horizon.

Middle Triassic conodonts from northeastern Spain: biostratigraphic implications

The facies development of the Spanish Triassic corresponds to the typical three-fold subdivision of the Germanic Facies: Buntsandstein, Muschelkalk and Keuper. Two intervals interpreted as epeiric carbonate platforms: lower Muschelkalk (Anisian) and upper Muschelkalk (Ladinian) are recognized during the Middle Triassic of northeastern Spain. These carbonate intervals are separated by one siliciclastic/evaporitic interval interpreted as sabbkha and saline deposits: middle Muschelkalk facies (Lower Ladinian). In northeastern Spain (Catalonian Coastal Ranges), two Middle Triassic sections comprising lower Muschelkalk facies have yielded the following conodont taxa: Paragondolella bulgarica, P. hanbulogi, P. bifurcata, Neogondolella constricta, N. cornuta, N. excentrica and N. basisymmetrica. The conodont sequence allows recognition of the P. bulgarica and N. constricta zones. These results indicate a middle–upper Pelsonian to upper Illyrian age (middle–upper Anisian), and represent the first conodont-chronostratigraphic approximation for the lower Muschelkalk facies of the western part of the Sephardic Province of the Triassic Tethys Realm.

Lower Devonian (Emsian) rugosa of the Izarne Formation, Montagne Noire, France

An account of the systematics, biostratigraphy, ecological setting and the biogeographic implications of rugose corals from olistoliths of the Cabrières area is given. Corals of the lower member of the Izarne Formation are dated by conodonts asgronbergiZone age, and includeLythophyllumsp. indet.,Calceola sandalina(Linné),Tryplasmasp. A,Breviphrentis rohartiPedder new species,B. exiguaPedder new species, andAqishaphyllumsp. A. Corals from the middle member of the formation includeFrechocystis pertinaxPedder new genus and species,Calceolasp. undet.,Rhizophyllumsp. aff.R. ukalundenseHill and Jell,Tryplasma enormePedder new species,Tryplasmasp. A,Breviphrentissp. A,Platysmatophyllum halleriPedder new genus and species,Pseudochonophyllum sentumPedder new species, andIzarneophyllum barroisi(Frech) new genus. No age significant conodont has been recovered from the middle member. However, scutelluid trilobites, which, together with other trilobites, evidently used the underside of Izarne corals for shelter during molting, provide correlation with conodont sequences in the nappe domain to the north and southwest of Cabrières. From this line of evidence, the middle Izarne coral fauna is deduced to benothoperbonusZone age. The association of a variety of benthic trilobites, all with large eyes, provides evidence of a photic zone environment for the middle Izarne corals.Rugose corals from the Izarne Formation belong to the Old World Realm and have nothing in common with similar age Rugosa of the Eastern Americas Realm. This implies that the dissolution of the boundary between these realms, which occurred in the Middle Devonian, did not begin before latest Emsian time.

Abstract: Wenlock Conodont Chronostratigraphy and Sequences of the Appalachian Basin in New York, Ohio, and Tennessee

Abstract: Wenlock Conodont Chronostratigraphy and Sequences of the Appalachian Basin in New York, Ohio, and Tennessee