Revision Of Stratigraphy Research Articles

Stratigraphic revision of the Miocene<b>“</b> Saikawa Formation<b>”</b> distributed in the southern Kanazawa area, Ishikawa Prefecture, central Japan.

石川県金沢市南部地域に分布する中新統“犀川層”の層序を岩相層序学・生層序学的研究から再検討した．ここでは，従来の“犀川層”を下位から，山科層，犀川層（再定義），小寺山層に区分した．山科層は泥岩を主体とし，珪藻化石帯NPD4Aの約15.6–15.4 Maを示す珪藻化石を含む．犀川層は主に粗粒砂岩からなり，得られた珪藻化石は再堆積であると考えられる．しかし，以前の研究で，CN5a帯（13.6–11.8 Ma）の石灰質ナノ化石が報告されている．これらのことは，犀川層が山科層を不整合に覆うことを示す．小寺山層は，細粒砂岩を主体とし，その基底礫岩は犀川層上部を侵食している．また，小寺山層は上位の更新統大桑層の基底礫岩に侵食されている．小寺山層からは，日本では3 Maまでに絶滅したカリア属（クルミ科）の内果皮が産出した．従って，大桑層は不整合で小寺山層を覆い，両者の間には130万年以上の堆積間隙があると考えられる．

Stratigraphy and paleoenvironmental analysis of the Frasnian-Famennian (Upper Devonian) boundary interval in Tioga, north-central Pennsylvania

Two pulses of extinction in the late Frasnian (Late Devonian), the Lower and Upper Kellwasser (LKW and UKW) events, coincided with the deposition of organic-rich strata in many parts of the world, including the Appalachian Basin. Here, we describe two stratigraphic sections from Tioga, north-central Pennsylvania, that span the Frasnian-Famennian (F-F) boundary interval. The F-F boundary and UKW-equivalent strata are probably located in the covered interval between the two sections, but the LKW-equivalent Pipe Creek Formation is well exposed. We propose several stratigraphic revisions, including raising the Lock Haven Formation to group status and dividing it into formations, as well as redefining the base of the Canaseraga Formation and subdividing it into members. Paleoenvironments at Tioga range from offshore/outer shelf to middle shoreface. A regression follows the LKW transgression, as evidenced by the sharp superposition of middle shoreface sands on outer-shelf mudstones, similar to large facies changes associated with the LKW in other settings. The LKW is typically interpreted as representing deposition under dysoxic-anoxic conditions, and trace and body fossil content suggest that the Pipe Creek Formation represents dysoxic but not permanently anoxic conditions. These stratigraphic revisions and records of environmental change will provide the framework for more detailed studies of the LKW and UKW extinction events in the Appalachian Basin.

Mesoarchean and Paleoproterozoic history of the Nimrod Complex, central Transantarctic Mountains, Antarctica: Stratigraphic revisions and relation to the Mawson Continent in East Gondwana

High-grade metamorphic and igneous rocks originally mapped as the Nimrod Group represent the only known crystalline basement of the East Antarctic shield exposed in the Transantarctic Mountains. SHRIMP U–Pb age data from zircon show that this assemblage preserves multiple geologic events spanning 2.5b.y. of Archean to early Paleozoic history, culminating in thermomechanical reworking and active-margin magmatism during the Ross Orogeny. New age data from igneous and metamorphic rocks, as well as from detrital zircons in metasedimentary quartzites, refine the Mesoarchean to Paleoproterozoic history and indicate the need to abandon the stratigraphic term Nimrod Group and its five formations. In its place, we redefine only the igneous and high-grade gneissic parts of the assemblage as the Nimrod Complex, and all other metasedimentary rocks exposed in the Miller and Geologists ranges are included in a newly defined Argosy Schist. Within the Nimrod Complex, the oldest layered gneisses represent magmatic Mesoarchean crust formed between about 3150 and 3050Ma. Correspondence of U–Pb zircon crystallization ages with whole-rock Sm–Nd model ages indicates formation from juvenile mantle melts. Magmatism at ca. 3100Ma was followed closely by high-temperature metamorphism, recorded by zircon crystallization at 2955–2900Ma, likely due to high advective heat transfer and/or thermal insulation of newly stabilized crust. Metaigneous units with ages of ca. 2500Ma indicate a late Neoarchean period of anatexis and/or magmatism, although the geologic context for these events is uncertain. Gneissic, eclogitic and metaigneous rocks record an important period of deep-crustal metamorphism, thickening and magmatism between 1730 and 1700Ma, referred to as the Nimrod Orogeny, that may have played an early role in assembly of East Gondwana cratons. A new lithodemic unit, Argosy Schist, consists of interlayered mica schist, quartzite, amphibolite, and calc-silicate schist. Quartzites from the schist unit have two distinctive detrital-zircon provenance characteristics; one type has populations that correlate with dated gneissic and metaigneous units of the Nimrod Complex, indicating a proximal provenance, whereas a second type has detrital zircon ages resembling those from Neoproterozoic Beardmore Group sandstones, indicating a common broader East Antarctic shield provenance. Their maximum depositional ages range widely from about 2000 to 900Ma, leaving unresolved their age and geologic relationship to either the Nimrod Complex or Beardmore Group, yet they comprise a metasedimentary assemblage that is distinctive from the Nimrod Complex. Recent findings of Mesoarchean gneisses in the Gawler Craton, geochronology from Terre Adélie, and our new age data from the Nimrod Complex thus highlight the importance of ca. 3.1, 2.5 and 1.7Ga events in formation of the composite East Antarctic shield adjacent to the modern Transantarctic Mountains. Correlative crustal units may extend to the southern Prince Charles Mountains and Shackleton Range. Collectively, this extensive crustal province, referred to as the Mawson Continent, represents an elongate belt of primary Mesoarchean crust that experienced major reworking at ca. 2.5 and 1.7Ga. The latter period includes both high- and low-P/T petrologic signatures, providing evidence of crustal thickening and magmatism that may signify collisional processes related to Paleoproterozoic cratonal amalgamation during formation of the Nuna supercontinent.

Tracking the early Silurian post-extinction faunal recovery in the Jupiter Formation of Anticosti Island, eastern Canada: A stratigraphic revision

Tracking the early Silurian post-extinction faunal recovery in the Jupiter Formation of Anticosti Island, eastern Canada: A stratigraphic revision

Stratigraphic revision of the Quaternary material from the vicinity of Belgrade and the Serbian segment of the Tisza valley analysed by V.D. Laskarev

In his studies of the Quaternary deposits in the vicinity of Belgrade and Vojvodina, V.D. Laskarev clearly identified the main Quaternary facies and lithostratigraphic units (loess series, Corbicula fluminalis beds, Holocene sands, etc.). Since the period of the publication of his research, there has been development in Quaternary stratigraphy and palaeogeography. In compliance with these changes, the following elements of his studies should be corrected:1) The age of the loess series in the Zemun Loess Plateau and the Belgrade Plateau corresponds to the younger part of the Middle and Late Pleistocene.2) The Pleistocene Corbicula beds represent temperate fluvial stages of the younger part of the Lower and Middle Pleistocene. The Viviparus boeckhi Horizon was defined as a subunit of the Pleistocene Corbicula beds that corresponds to the younger part of the Lower Pleistocene fluvial temperate stages. The Makiš beds should be defined as a local term for the Pleistocene Corbicula beds in the Sava valley (in the vicinity of Belgrade).3) Laskarev generally recognized the main features of the Quaternary palaeogeographic evolution; however, they cannot be applied to the whole area of the Serbian segment of the Pannonian Plain.There are still no reliable geological data for the Lower and Middle Pleistocene parts of the Quaternary geological sections such as the Zrenjanin–Titel Loess Plateau. It is evident that up to now the Pleistocene Corbicula beds have not been identified in the basement of the Titel Loess Plateau, only the aeolo-lacustrine and lacustrine–palustrine silts underlying the loess series.4) Geomorphological investigations have identified four terraces in the valley of the Danube and the Tisza in Vojvodina. In this case, the first terrace level of Laskarev should be divided into the lower Ia or t1 and upper Ib or t2 terraces.

Geochronologic and stratigraphic constraints on the Mesoproterozoic and Neoproterozoic Pahrump Group, Death Valley, California: A record of the assembly, stability, and breakup of Rodinia

Research Article| May 01, 2014 Geochronologic and stratigraphic constraints on the Mesoproterozoic and Neoproterozoic Pahrump Group, Death Valley, California: A record of the assembly, stability, and breakup of Rodinia Robert C. Mahon; Robert C. Mahon 1Idaho State University Department of Geosciences, 921 S. 8th Ave., Stop 8072, Pocatello, Idaho 83209-8072, USA †Current address: University of Wyoming Department of Geology and Geophysics, Department 3006, 1000 University Ave., Laramie, Wyoming 82071, USA; e-mail: mahorobe@isu.edu; rmahon1@uwyo.edu. Search for other works by this author on: GSW Google Scholar Carol M. Dehler; Carol M. Dehler 2Utah State University Department of Geology, 4505 Old Main Hill, Logan, Utah 84322-4505, USA Search for other works by this author on: GSW Google Scholar Paul K. Link; Paul K. Link 1Idaho State University Department of Geosciences, 921 S. 8th Ave., Stop 8072, Pocatello, Idaho 83209-8072, USA Search for other works by this author on: GSW Google Scholar Karl E. Karlstrom; Karl E. Karlstrom 3University of New Mexico Department of Earth and Planetary Sciences, MSCO3-2040, Albuquerque, New Mexico 87131, USA Search for other works by this author on: GSW Google Scholar George E. Gehrels George E. Gehrels 4University of Arizona Department of Geosciences, 1040 E. 4th St., Tucson, Arizona 85721, USA Search for other works by this author on: GSW Google Scholar GSA Bulletin (2014) 126 (5-6): 652–664. https://doi.org/10.1130/B30956.1 Article history received: 07 Jul 2013 rev-recd: 03 Dec 2013 accepted: 08 Jan 2014 first online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Robert C. Mahon, Carol M. Dehler, Paul K. Link, Karl E. Karlstrom, George E. Gehrels; Geochronologic and stratigraphic constraints on the Mesoproterozoic and Neoproterozoic Pahrump Group, Death Valley, California: A record of the assembly, stability, and breakup of Rodinia. GSA Bulletin 2014;; 126 (5-6): 652–664. doi: https://doi.org/10.1130/B30956.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The Pahrump Group in the Death Valley region of eastern California records a rich history of Mesoproterozoic to Neoproterozoic tectonic, climatic, and biotic events. These include the formation, stability, and onset of rifting of the Rodinia supercontinent, two potentially low-latitude glaciations correlative with global “snowball Earth” glacial intervals, and the onset of complex microbiota (e.g., testate amoebae). Poor direct age control, however, has significantly hindered the progress of understanding of these important stratigraphic units. New LA-ICPMS (laser ablation–inductively coupled plasma mass spectrometry) detrital zircon data from clastic units directly overlying a major unconformity within the Mesoproterozoic Crystal Spring Formation provide a maximum depositional age of 787 ± 11 Ma for the upper member of the Crystal Spring Formation. This unconformity, representing a duration of ≥300 Ma, is now recognized in sedimentary successions across southwestern Laurentia. These new age data, in addition to the distinct stratigraphic style above and below the unconformity, result in the proposed formal stratigraphic revision to elevate the upper member of the Crystal Spring Formation to the Neoproterozoic Horse Thief Springs Formation and separate it from the remainder of the underlying Mesoproterozoic Crystal Spring Formation (ca. 1100 Ma). New age relations and revised stratigraphic nomenclature significantly clarify stratigraphic and tectonic correlations and imply ca. 1250–1070 Ma assembly, 1070–780 Ma stability, and 780–600 Ma breakup of the supercontinent Rodinia along the southwestern Laurentian margin. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Geochronological constraints on nickel metallogeny in the Lake Johnston belt, Southern Cross Domain

Geochronology and stratigraphic revision of the Lake Johnston greenstone belt and adjacent granitoids and granitic gneiss provide new insight into the age of komatiites in the Southern Cross Domain of the Archean Yilgarn Craton. Roundtop Komatiites are geochemically similar to undated komatiites in the adjacent Ravensthorpe and Southern Cross—Forrestania greenstone belts, and the results can be extrapolated to improve the regional understanding and geodynamic evolution. Consequently, the further refined knowledge of the regional stratigraphy improves the understanding of the evolution and targeting of komatiite-hosted nickel deposits. A minimum age of ca 2773 Ma for the succession of the Lake Johnston greenstone belt is provided by crosscutting granitic rocks, with a maximum age for the underlying Roundtop Komatiite given by a maximum depositional age of ca 2876 Ma for felsic volcaniclastic rocks of the underlying Honman Formation. These new results suggest that komatiites of the Southern Cross Domain are significantly younger than previously assumed, which has implications for Yilgarn-wide geodynamic models regarding ‘plume activity’ and global correlations in the Meso- to Neoarchean.

Deformation and stratigraphic evolution of the Ligurian Accretionary Complex in the southern Apennines (Italy)

This work provides a structural analysis and a stratigraphic revision of the sedimentary successions of the Ligurian Accretionary Complex (LAC) cropping out in the southern Apennines along the boundary between Campania, Lucania and Calabria regions. Two fold and thrust sets characterize the progressive deformation related to the Early Miocene inclusion of these successions in the tectonic accretionary wedge. A third deformation stage, affecting also the Middle-Upper Miocene unconformable wedge-top basin deposits, is associated to the thrust front eastward migration. In this orogenic phase the Apennine thrust sheet pile, formed by LAC and Apennine Platform Units, tectonically covered the successions located in the westernmost sector of the Lagonegro-Molise Basin. Finally a Pliocene-Middle Pleistocene regional fold set deformed the whole orogenic prism as consequence of a thick-skinned tectonics expressed by means of deeply rooted thrusts in the buried Apulian Platform carbonates. Maghrebian Flysch Basin and LAC successions show a similar stratigraphy indicating continuity between paleogeographic basin domains, as well as between the Paleogene-Lower Miocene succession of Sicilide Unit and the corresponding deposits of Lagonegro-Molise Basin as consequence of drowning of the interposed Panormide Platform starting from the uppermost Cretaceous.

The “Continental Intercalaire” of southern Tunisia: Stratigraphy, paleontology, and paleoecology

The “Continental Intercalaire” deposits of southern Tunisia preserve one of the most diverse Early Cretaceous vertebrate fauna from Africa, consisting of elasmobranchs, actinopterygians, sarcopterygians, turtles, crocodyliforms, pterosaurs, and non-avian dinosaurs. Vertebrate remains representative of both marine and fluvial environments have been historically referred to a specific bonebed within the Chenini Member, which crops out extensively in the Tataouine region. A stratigraphic revision of the mainly siliciclastic deposits of the Douiret and the Aïn El Guettar formations in the area based on new sedimentological and paleontological data is presented. Data collected indicate the presence of multiple fossil-bearing strata encompassing the stratigraphic interval from the Berriasian to the Albian and document faunal variation through time as well as major environmental and climatic changes. Detailed sedimentological analysis combined with biostratigraphic correlation performed at a basin scale indicate lateral facies variability within each formation as a result of tectonically and climatically driven zonations within the Tataouine Basin in the Early Cretaceous. Furthermore, proposed stratigraphic correlations indicate that vertebrate remains previously referred to the fluvial Chenini Member (and in particular theropod and sauropod dinosaurs) are instead representative of a transgressive deposit which mark the base of the overlying Oum ed Diab Member.

Stratigraphic revision of the Green River Formation in Fossil Basin, Wyoming

Research Article| January 01, 2011 Stratigraphic revision of the Green River Formation in Fossil Basin, Wyoming H. Paul Buchheim; H. Paul Buchheim ∗ 1Department of Earth and Biological Sciences, Loma Linda University, Loma Linda, California 92350, U.S.A. ∗Correspondence should be addressed to: pbuchheim@llu.edu Search for other works by this author on: GSW Google Scholar Robert A. Cushman, Jr.; Robert A. Cushman, Jr. 2Department of Biological Sciences, Walla Walla University, College Place, Washington 99324, U.S.A. Search for other works by this author on: GSW Google Scholar Roberto E. Biaggi Roberto E. Biaggi 3Ciencias Naturales, Universidad Adventista del Plata, Libertador San Martin, Entre Rios 03103, Argentina Search for other works by this author on: GSW Google Scholar Rocky Mountain Geology (2011) 46 (2): 165–181. https://doi.org/10.2113/gsrocky.46.2.165 Article history received: 04 Mar 2011 rev-recd: 13 Sep 2011 accepted: 11 Nov 2011 first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation H. Paul Buchheim, Robert A. Cushman, Roberto E. Biaggi; Stratigraphic revision of the Green River Formation in Fossil Basin, Wyoming. Rocky Mountain Geology 2011;; 46 (2): 165–181. doi: https://doi.org/10.2113/gsrocky.46.2.165 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu nav search search input Search input auto suggest search filter All ContentBy SocietyRocky Mountain Geology Search Advanced Search Abstract The Eocene Green River Formation in Fossil Basin, Wyoming provides a detailed record of the paleoecology and depositional history of ancient Fossil Lake. Fossil Lake was one of three Eocene lakes that formed an extensive lake system in Wyoming, Utah, and Colorado. It began as a flood-plain lake in the southern part of Fossil Basin and expanded northward as the lake evolved. Fossil Lake went through the major stages of lake evolution, including the overfilled (Road Hollow Member), balanced-fill (Fossil Butte Member), and underfilled (Angelo Member) stages. These stages are represented in the sedimentary record by a complete suite of lake-margin to lake-center facies.This study establishes the Road Hollow Member of the Green River Formation as representing the earliest stage of lake evolution in Fossil Lake. We also revise the boundaries for the Fossil Butte and Angelo Members of the Green River Formation, which clearly delineate the latest two stages of lake evolution. These revisions not only describe and add a previously unrecognized and thick sequence of lacustrine rocks in Fossil Basin, but help us to better understand the depositional systems that existed during each stage of lake evolution. You do not currently have access to this article.

The Los Llantenes Formation in the Precordillera of Jagüe (La Rioja Province) and the recognition of a rifting stage in the early evolution of the late Paleozoic basins in western Argentina.

In the northern part of the Argentine Precordillera, northwestern La Rioja, the Upper Paleozoic is over 4,000 m thick. Very coarse conglomerates from the basal section have not been described nor adequately interpreted. This work analyses this unit in the context of a stratigraphic revision of the upper Paleozoic of the region, and interprets the conglomerate as a rift deposit. The thick (>1,000 m) and coarse purple conglomeratic succession, herein named ‘Los Llantenes Formation’, non-conformably rests on the basement rocks of the region and underlies deposits of the first glacial record associated with the Gondwanan glaciation. While its great thickness and restricted areal extent indicate localized subsidence, the crude stratification, poor sorting and abundance of >1-m boulders indicate an origin related to high-gradient, low-efficiency alluvial fans. Their composition and coarse-grained size indicate local provenance, abrupt relief and incipiently developed drainage systems and a highly compartmentalized and abrupt paleogeography. A complex glacial history generated deep ‘U’-shaped paleovalleys in the Los Llantenes Formation, developing paleovalleys that accommodated basal lodgment tills and glacial diamictites with sedimentologic features comparable to the Cerro Tres Condores Formation (Visean in age) exposed to the south. The age of the conglomerates of Los Llantenes Formation, clearly preglacial, can be stratigraphically bracketed between the Middle Devonian substrate cropping out to the south in the sierra de Las Minitas and the Middle Mississippian, age of the Cerro Tres Condores Formation. Consequently, Los Llantenes Formation may partly correlate with the Agua de Lucho Formation (Tournaisian-Vissean) that in the area of Rio del Penon, immediately to the south, underlies the glacigenic Cerro Tres Condores Formation. Mapping relationships with limited areal extent, together with the great thickness of Los Llantenes Formation and the local provenance, allow interpreting accommodation in extensional or pull-apart depocenters, conclusions that are relevant in order to reconstruct the history of the basin.

Estratigrafia, arquitetura deposicional e faciologia da formação Missão Velha (Neojurássico-Eocretáceo) na área-tipo, bacia do Araripe, nordeste do Brasil: exemplo de sedimentação de estágio de início de rifte a clímax de rifte

The aim of this study was to carry out a stratigraphic revision of the Missão Velha Formation (Araripe Basin, northeastern Brazil) based on detailed facies analysis, architectural elements, depositional systems and palaeoflow data. The main facies are: 1. coarse-grained conglomeratic sandstones and locally pebbly conglomerates, with abundant silicified fossil trunks, several large-to medium-scale trough cross-stratifications and predominantly lenticular geometry; 2. medium-to coarse-grained lenticular sandstones with granules, abundant silicified fossil wood and trunks, and large-to medium-scale trough cross-stratifications, cut-and-fill features and mud drapes on the foreset cross-strata; 3. conglomerates and poorly sorted medium-grained sandstones with sparse pebbles and horizontal stratification; 4. fine-to very fine-laminated silty sandstone interlayered with 5. decimetric pelitic layers with parallel stratification and climbing-ripple cross-lamination. Ten architectural elements were identified: CH: Channels, GB: Gravel bars and bedforms, SG: sediment gravity flows, SB: Sand bars and bedforms, SB(p): sand bedform with planar cross-stratification, OFch: Overbank flow of channel (levee, crevasse and channel splay), DA: Downstream-accretion macroforms, LS: Laminated sand-sheet, LA: Lateral-accretion macroforms and FF: Floodplain fines. Not all of these features were observed at each outcrop. These elements, which are defined by their geometry and bounding surfaces, form the basis for interpreting depositional environments. The Missão Velha Formation is interpreted as: a. high energy braided fluvial systems with fining-upward cycles, channelized features, truncated cross-strata (diastema), lenticular geometry, channeled sandstones, sparse pebbles and b. meandering river systems due to the presence of flood plain deposits, crevasse splays and point-bars deposits. Aeolian deposits can also occur.

Orbitolinid foraminifers in the Northwest Pacific: Their taxonomy and stratigraphy

Orbitolinid foraminifers supply important information for the understanding of Cretaceous marine biogeographic and paleoclimatic conditions. A pre-requisite for these palaeoenviromental interpretations is a sound taxonomy. The taxonomy of the orbitolinids from the Northwest Pacific has been controversial, and this paper aims at a taxonomic and stratigraphic revision of this group. Four orbitolinid species ("Palorbitolina lenticularis", Praeorbitolina cf. wienandsi, Mesorbitolina parva, and M. texana) have been recognized. Orbitolinids occurred almost continuously from the Late Hauterivian to the late Early Albian. Species belonging to the Praeorbitolina cormyi–Mesorbitolina aperta evolutionary lineage are most common, while dictyoconids are missing in the Northwest Pacific. Following the last occurrence ofM. parva in the Douvilleiceras mammilatum Zone of the Early Albian, no orbitolinids have been recognized in the Northwest Pacific. It is possible that provincialism in orbitolinid foraminifers occurred during the Early Cretaceous of the North Pacific.

Stratigraphic ranges of Mesozoic radiolarian families

The recent systematic and stratigraphic revision of all described Mesozoic radiolarian genera ( O’Dogherty et al., 2009a,b,c) represents the state of the art in the taxonomy of this group. Using this information, we have improved the stratigraphy of Mesozoic families by redefining their ranges at the substage precision. Our analysis shows a clear change in faunal composition at the Permo–Triassic boundary (only 15 families cross: 2 Albaillellaria, 4 Latentifistularia, 3 Entactinaria, 2 Nassellaria and 4 Spumellarian) followed by an explosion at the Middle Triassic. Through the Late Triassic, 32 families began to go extinct, leading to a drastic disappearance of typical Triassic morphotypes. However, the Triassic–Jurassic boundary does not record a similar extinction at the family level; 37 families and subfamilies apparently crossed the boundary. Paradoxically, the revision of genera has shown the survival of only 30 genera at this boundary belonging to 23 families. The reason of such a discrepancy is the virtual crossing of 14 families at Triassic–Jurassic boundary. That is, families having representatives in both the Triassic and Jurassic, but without any record close to the boundary. Similarly, these discontinuities in the ranges are observed throughout the Jurassic and Cretaceous, but especially at the Cretaceous–Paleogene boundary, where 21 families are crossing virtually. Among the orders, Entactinaria presents proportionally the highest number of families with discontinuous ranges. The reason could be related to the scarcity of studies on this group whose systematic classification needs a good knowledge of the initial spicule. We analyze in detail the major discontinuities observed in the range of some families. Explanations considering discontinuous fossil record, limited knowledge on phylogenetic relationships, or possible homeomorphism are proposed.

Stratigraphic revision of the Cenozoic deposits of the Lungro-Verbicaro Unit (Northern Calabria): new data for the reconstruction of tectonic evolution of the southern Apennines

Field and biostratigraphic data from Cenozoic metasedimentary succession («breccia a selce», Colle Trodo and «Scisti del Fiume Lao» Formations) of Lungro-Verbicaro Unit are reported. The «Scisti del Fiume Lao» Formation, formerly included in the ophiolite-bearing Frido Unit, defined at the Calabria-Lucania border area, is interpreted as the stratigraphic uppermost part of the above Cenozoic succession. Therefore, the occurrence of nannofossil assemblage not older than late Aquitanian, represents the minimum age constrain both to the deformation and to the HP/LT metamorphic event affecting the Lungro-Verbicaro Unit. This age is in agreement with the Burdigalian radiometric age recognized in metavolcanic and metapelitic rocks of Lungro-Verbicaro Unit.

The Late Triassic (Norian) Adamanian–Revueltian tetrapod faunal transition in the Chinle Formation of Petrified Forest National Park, Arizona

ABSTRACTRecent stratigraphic revisions of the Upper Triassic Chinle Formation of Petrified Forest National Park, in conjunction with precise and accurate documentation of fossil tetrapod occurrences, clarified the local biostratigraphy, with regional and global implications. A significant overlap between Adamanian and Revueltian faunas is rejected, as is the validity of the Lamyan sub-land vertebrate faunachron. The Adamanian–Revueltian boundary can be precisely placed within the lower Jim Camp Wash beds of the Sonsela Member and thus does not occur at the hypothesised Tr-4 unconformity. This mid-Norian faunal turnover, may coincide with a floral turnover, based on palynology studies and also on sedimentological evidence of increasing aridity. Available age constraints bracketing the turnover horizon are consistent with the age of the Manicouagan impact event. The rise of dinosaurs in western North America did not correspond to the Adamanian–Revueltian transition, and overall dinosauromorph diversity seems to have remained at a constant level across it. The paucity of detailed Late Triassic vertebrate biostratigraphic data and radioisotopic dates makes it currently impossible to either support or reject the existence of globally synchronous Late Triassic extinctions for tetrapods.

Revisión taxonómica y estratigráfica de esporas cicatricosas del Cretácico Inferior de Patagonia. 2. Géneros Cicatricosisporites Potonié & Gelletich y Ruffordiaspora Dettmann & Clifford

Taxonomic and stratigraphic revision of Lower Cretaceous cicatricose spores from Patagonia. 2. Genera Cicatricosisporites Potonie & Gelletich and Ruffordiaspora Dettmann & Clifford. Nine species of the genus Cicatricosisporites and five species of the genus Ruffordiaspora were found in several surface and subsurface sections of Lower Cretaceous sediments from the Austral Basin, Patagonia, Argentina. Two new species: Cicatricosisporites pramparoana and Ruffordiaspora cardielensis, are described, while 5 species: Cicatricosisporites cf. C. hallei, C. minutaestriatus, C. venustus, Ruffordiaspora cf. R. crassiterminatus nov. comb. and R. ludbrookiae are mentioned for the first time in Argentina. In view of the similarities that may be found between some species, and in order to facilitate comparisons and determinations, the main characters for each taxon here considered are resumed in a table. It is concluded that during the Lower Cretaceous spores of the family Anemiaceae were frequent components of pollen assemblages from the Austral Basin. Three groups of species studied are recognized: 1) species that are present in all stages of the Lower Cretaceous (Cicatricosisporites annulatus, C. cuneiformis, C. hughesii, C. sp. 2, Ruffordiaspora australiensis, R. ludbrookiae and R. ticoensis), 2) species that are found only in Aptian and Albian deposits (Cicatricosisporites cf. C. hallei, C. pramparoana and Ruffordiaspora cardielensis), and 3) species present excusively in albian sediments (Cicatricosisporites venustus, C. minutaestriatus and Ruffordiaspora cf. R. crassiterminatus).

Revisión taxonómica y estratigráfica de esporas cicatricosas del Cretácico Inferior de Patagonia. 1. Géneros Appendicisporites Weyland & Krieger, Nodosisporites Deák y Plicatella Maljavkina

Taxonomic and stratigraphic revision of Lower Cretaceous cicatricose spores from Patagonia. 1. Genera Appendicisporites Weyland & Krieger, Nodosisporites Deák and Plicatella Maljavkina. Lower Cretaceous sediments found in different localities of the Austral Basin in Patagonia, contain several cicatricose fern spore types belonging to the family Anemiaceae. This initial contribution is a taxonomic study of 13 species referred to the genera Appendicisporites Weyland & Krieger, Nodosisporites Deák and Plicatella Maljavkina. The most recent criteria to characterise these genera are discussed and systematic changes of taxa previously described in Argentina are suggested. The material was recovered from Valanginian to Albian lithostratigraphic units found in surface sections and offshore well cores of the Continental Platform. Nodosisporites cf. N. genuinus (Bolkhovitina) Davies, Appendicisporites cf. A. unicus (Markova) Singh, Plicatipollenites jansonii (Pocock) Davies, P. cf. P. degenerata (Thiergart) Davies and P. pseudotripartita (Bolkhovitina) nov. comb. are described for the first time in Argentina. The new name and new combination Plicatipollenites archangelskyi Davies (for Cicatricosisporites giganteus Archangelsky & Gamerro 1966), and the new combination Plicatipollenites baqueroensis (Archangelsky & Gamerro) Davies are accepted. Finally, comments on the stratigraphic distribution of the studied species in surface sections and well cores are made.

Stratigraphy of the Upper Cretaceous Wapiti Formation, west-central Alberta, Canada

The lithostratigraphic interval between the marine Puskwaskau Formation (Smoky Group, Santonian–Campanian) and the fluvial Scollard Formation (early Maastrichtian) in west-central Alberta and easternmost British Columbia (Canada) is represented by the nonmarine deposits of the Wapiti Formation. Its subdivision into regionally mappable stratigraphic units and the correlation of such units with the better known successions of central and southern Alberta are the main goals of this study. We present a detailed stratigraphic revision of the Wapiti Formation in the Grande Prairie region, where the entire succession crops out extensively and intensive oil and gas exploration activity provides excellent subsurface control. This study indicates that the Wapiti Formation consists in five stratigraphic units: their description has been based in particular on facies analysis and well-log signatures. In ascending order, units 1 to 5 record major differences in depositional architecture related to variation in accommodation and climatic conditions. Upper and lower contacts of these units are represented by regionally mappable subaerial unconformities or conformable facies contacts. Three major coal zones are identified within the Wapiti Formation, the Basal, Red Willow, and Cutbank: coals referred to these intervals have been documented in both outcrop and subsurface in the entire study area, thus representing a reliable tool for regional correlations. Furthermore, results presented here indicate that the maximum flooding surfaces of the Bearpaw seaway and the Drumheller Marine Tongue, both marine reference units in central and southern Alberta, lie, respectively, within coals of unit 3 and the Red Willow coal zone.

A Review of the Endocerid CephalopodProtocyptendocerasfrom the Floian (Lower Ordovician) of the Eastern Cordillera, Argentina

Ordovician cephalopods from Western Gondwana are still poorly known and published data is in need of systematic and stratigraphical revision. In this work, the endocerid proterocameroceratid Protocyptendoceras from the Floian of the Eastern Cordillera of Argentina is revised using new material from La Cienaga, 5 km upstream from Purmamarca. The species P. corvalani and P. teicherti are considered to be junior synonyms of P. fuenzalidae, which is redescribed in detail and reillustrated. Specimens preserve adapical parts of isolated siphuncles, related here to the presence of endocones in a posterior portion. Evidently P. fuenzalidae had a nektobenthic mode of life in a shallow water environment, oriented horizontally. Its palaeobiogeographical affinities are mainly with Floian proterocameroceratids from Eastern Gondwana, such as Anthoceras decorum and the related genera Lobendoceras, Ventroloboceras, and Notocycloceras.