%0 Journal Article %J Geological Magazine %D 2019 %T Comment on: Álvaro, J. J., Esteve, J. & Zamora, S. 2019. Morphological assessment of the earliest paradoxidid trilobites (Cambrian Series 3) from Morocco and Spain %A G. Geyer %A Nowicki, Jakub %A Żylińska, Anna %A E. Landing %K Anti- Atla %K Biostratigraphy %K Iberian Chains %K morphometrics %K trilobite systematics %K West Gondwana %X
Álvaro et al. (2018) argued that at least six species of Acadoparadoxides described from the lower–middle Cambrian boundary interval successions in the Anti-Atlas of Morocco all belong to Acadoparadoxides mureroensis (Sdzuy, 1958), which was first described from the Iberian Chains, Spain. Their study is based entirely on a morphometric analysis, which ignores the stratigraphic occurrences of particular morphotypes, deformation-related compaction of individual sclerites and their original relief, and thus underestimates some of the earlier
described differences between these species. Their synonymization of a number of named Acadoparadoxides species is based on the morphometric approach that they rely on to distinguish between a number of congeneric species. A morphometric approach as applied by Álvaro et al. will lead to an apparent synonymy based on sclerites of similar taxa. Thus, morphometric study must be complemented by an analysis of which morphologically distinctive sclerites (i.e. cranidia and pygidia) are stratigraphically associated, and evaluation of which measurements are more critical to distinguishing sclerites that may represent distinct taxa, and the recognition of related character sets. Apart from demonstrating problems in the conclusion of Álvaro et al., our more inclusive approach of morphologic and stratigraphic analysis works to reassert the diagnostic characters and differences between six earlier named species of Acadoparadoxides. Our conclusions also emphasize the taxonomic problems associated with the identification and morphological variation of A. mureroensis owing to tectonic deformation of its topotype material and to questionable taxonomic assignment of Acadoparadoxides specimens from the Iberian sections.
New investigations of the Cambrian in the Franconian Forest region lead to a revision of the lithostratigraphic succession into seven units: Rauschbach Unit, Tiefenbach Formation, Tannenknock Formation (with Galgenberg and Wildenstein members), Triebenreuth Formation, Lippertsgrün Formation and Bergleshof Formation, with partly revised stratigraphical ranges and lithological characteristics. The succession indicates a fairly complete succession from Cambrian Series 2 (late early Cambrian) through the end of the Miaolingian, with gaps being a result of incomplete exposure and structural complexity rather than distinct hiatuses. New finds expand the known fossil record and provide additional data for reconstructing biogeographical relationships and depositional environments. These features indicate shallow marine conditions throughout the Cambrian with characteristics typical for West Gondwanan shelf areas. In particular, strong similarities to the Moroccan Atlas regions are indicated. Additional information on volcanic activity from middle Cambrian through Tremadocian times provides clues for crustal extension that affected the depositional setting in this region. Stratigraphy, depositional environments and facies distribution all suggest reinterpretation of earlier geotectonical models used to interpret the history of the Franconian Forest area in the Saxothuringian Belt.
%B Newsletters on Stratigraphy %V 52 %P 377-433 %G eng %U https://dx.doi.org/10.1127/nos/2019/0495 %N 4 %R 10.1127/nos/2019/0495 %0 Book Section %B Earth System Evolution and Early Life: A Celebration of the Work of Martin Brasier %D 2016 %T The Precambrian–Phanerozoic and Ediacaran–Cambrian Boundaries: A Historical Approach to a Dilemma %A G. Geyer %A E. Landing %E Brasier, A. T. %E McIlroy, D. %E McLoughlin, N. %XThe Cambrian was originally defined as a rock interval with a trilobite-dominated fauna that overlay a presumed biologically barren Precambrian epoch. Work to formally define the Cambrian base arose after the discovery of Precambrian macrofossils in South Australia. The Working Group on the Precambrian–Cambrian Boundary (set up in 1972) promoted an emphasis on an extended pre-trilobitic interval with mineralized skeletal elements (small shelly fossils or early skeletal fossils). The study of early skeletal fossils made the Ulakhan-Sulugur (Siberia) and Meishucun (South China) sections candidates for the basal Cambrian Global Stratotype Section and Point (GSSP), but difficulties in correlation and the taxonomy of early skeletal fossils did not allow the selection of a reliably correlative horizon. Bilaterian ichnofaunas below the first diverse early skeletal fossils suggested the definition of a Cambrian base GSSP below the early skeletal fossils. Work on the thick, stratigraphically continuous and fairly unifacial sections in the Burin Peninsula, southeastern Newfoundland led in 1992 to an ichnofossil-defined GSSP at Fortune Head. Despite arguments for a revision and redefinition of the lower boundary of the Cambrian System, the best definition of the basal Cambrian GSSP is at Fortune Head and does not rely on the Treptichnus/Trichophycus pedum (abbreviated below as T. pedum) first appearance datum, but rather on the base of the T. pedum Assemblage Zone at the highest occurrence of Ediacaran taxa and in the lower range of T. pedum.
%B Earth System Evolution and Early Life: A Celebration of the Work of Martin Brasier %I Geological Society of London %C London, England %V Special Publication 448 %P 311-349 %G eng %U http://sp.lyellcollection.org/content/early/2016/11/01/SP448.10 %& 10 %R 10.1144/SP448.10 %0 Book Section %B Morocco 2006. Ediacaran-Cambrian Depositional Environments and Stratigraphy of the Western Atlas Regions. Explanatory Description and Field Excursion Guide %D 2006 %T Latest Ediacaran and Cambrian of the Moroccan Atlas Regions %A G. Geyer %A E. Landing %E G. Geyer %E E. Landing %K Cambrian %K latest Ediacaran %K lithostratigraphy %K Moroccan Atlas %XThe characteristics of the latest Ediacaran through Cambrian of the Moroccan Atlas regions are described and illustrated. Such major depositional controls as tectonic environments (a transtensional regime in this time interval) and eustatic changes that defined sequence boundaries and „Grand cycles,“ as well as a progressive southerly movement of the West Gondwanan margin that led to the loss of tropical carbonate platform facies and their replacement by siliciclastic-dominated successions in the Lower–Middle Cambrian boundary interval, are discussed briefly. The lithostratigraphic units for the uppermost Proterozoic(?) to the Upper Cambrian of the Moroccan Anti-Atlas and High Atlas mountains are reviewed and partly revised. The descriptions of lithostratigraphic units include lithology, depositional environments, fossil content, and synonymy. The Jbel Wawrmast Formation is divided into a lower Brèche à Micmacca Member and an upper Tarhoucht Member (new) that comprises the majority of the formation. The bio- and chronostratigraphy of the Atlas regions are summarized, and recently proposed, formal and informal biostratigraphical units of the Lower–Middle Cambrian are reviewed. Detailed stratigraphy allows recognition of diachroneity for several formational contacts. Controversial data and problems of the Moroccan Precambrian–Cambrian boundary are discussed in detail. The available evidence does not permit highly resolved certainty in correlations even at the stage-level with Lower Cambrian sections on other Cambrian continents. However, close similarities exist in the litho- and biostratigraphic developments of southern Morocco and Iberia, and demonstrate that both regions were coterminous on the West Gondwanan margin and geographically separated from the Avalon microcontinent by the latest Proterozoic.
%B Morocco 2006. Ediacaran-Cambrian Depositional Environments and Stratigraphy of the Western Atlas Regions. Explanatory Description and Field Excursion Guide %S Beringeria Special Issue %P 7-46 %G eng %0 Generic %D 2006 %T Morocco 2006. Ediacaran-Cambrian depositional Environments and Stratigraphy of the Western Atlas Regions. Explanatory Description and Field Excursion Guide %A G. Geyer %A E. Landing %K geology %B Beringeria Special Issue %C , %G eng %0 Book Section %B Morocco 2006. EdiacaranCambrian Depositional Environments and Stratigraphy of the Western Atlas Regions. Explanatory Description and Field Excursion Guide %D 2006 %T Morocco Field Excursion 2006. Ediacaran-Cambrian Depositional Environments and Stratigraphy of the Western Atlas Regions %A G. Geyer %A E. Landing %E G. Geyer %E E. Landing %K Biostratigraphy %K Cambrian %K Ediacaran %K intercontinental correlation %K lithostratigraphy %K Moroccan Atlas regions %K paleoenvironments %K sequence boundaries %K volcanic ash occurrences %XThis field excursion emphasizes paleoenvironments, litho- and biostratigraphy, sequence boundaries, volcanic ash occurrences, and potential for intercontinental correlation of a number of important Ediacaran and Cambrian sections of the Moroccan Atlas regions. The arrangement of the sections visited during the field excursion from December 2 to 5, 2006, begins on the northern slope of the western Anti-Atlas with the lowest Cambrian at Tiout and the lower part of the trilobite-bearing Cambrian at Tazemmourt. Complete sections through the trilobite-bearing Cambrian in the Lemdad syncline feature the Cambrian in the western High Atlas range. The subsequent drive across the western Anti-Atlas shows aspects of post-Pan-African Proterozoic, siliciclastic facies with archaeocyathan bioherms in the Issafen Syncline, and spectacular slump-folding of the Lie de vin Formation as well as a siliciclastical-dominated Lower and fossiliferous Middle Cambrian in the Tata region. The final day in the field features the Devonian and the siliciclastic Middle Cambrian along the southern flank of the western Anti-Atlas and carbonate-dominated Lower Cambrian at the western rim of the Anti-Atlas.
Information on the stops includes a summary of the lithologic sequence and, if available, a complete list of faunas found at successive levels. The sample numbers with the prefix F refer either to the faunal levels of HUPÉ (1953, 1959) or SDZUY (1978); sample numbers with a comma indicate a precisely measured level above the base of the section or unit; other samples refer to horizons reported by G. GEYER (e.g., 1986, 1988b, 1990c, 1998) or to subsequent collections by the authors and W. HELDMAIER (1997).
%B Morocco 2006. EdiacaranCambrian Depositional Environments and Stratigraphy of the Western Atlas Regions. Explanatory Description and Field Excursion Guide %S Beringeria Special Issue %P 47-112 %G eng %0 Journal Article %J Acta Geologica Polonica %D 2004 %T A Unified Lower-Middle Cambrian Chronostratigraphy for West Gondwana %A G. Geyer %A E. Landing %K Agdzian Stage %K Atlasian Series %K Australia %K Cambrian %K Celtiberian Series %K chronostratigraphy %K Cordubian Series %K Israel %K Jordan %K Morocco %K Poland %K Siberia %K South China %K Spain %K Trilobita %XSimilarities in biotic successions support a unified, composite chronostratigraphy for the Lower-Middle Cambrian of the Iberian and Moroccan margins of West Gondwana. The Cordubian Series (emended from an Iberian stage-level unit) comprises the sub-trilobitic Lower Cambrian of West Gondwana. This series represents ca. half of the Cambrian (ca. 25 m.y.), has a base defined at the lowest occurrence of diagnostic Cambrian ichnogenera in central Spain, and is comparable to the Placentian Series of Avalon. The overlying trilobite-bearing Lower Cambrian (ca. 9 m.y. duration), or Atlasian Series (new), of West Gondwana consists of two stages originally defined in highly fossiliferous (trilobites and archaeocyaths) Moroccan sections where they have great potential for precise U-Pb geochronology. The penultimate Lower Cambrian stage, the Issendalenian, with the near-joint lowest occurrence of trilobites and archaeocyaths, is approximately comparable with the sparsely fossiliferous, Iberian "Ovetian Stage" (designation abandoned). The "Ovetian" as currently revised is invalid because it is an objective homonym of SDZUY’s original “Ovetian.” The "Ovetian" is not a practically applicable unit as its basal stratotype horizon lacks any identified fossils, and its trilobites are so rare that it cannot serve as a standard for interregional correlation. By contrast, the Banian Stage as defined in Morocco is suitable as the terminal Lower Cambrian stage of West Gondwana. It is based on very fossiliferous successions that allow recognition of three successive trilobite zones and is similar in concept to the Iberian “Marianian Stage” (designation abandoned). The “Marianian” lacks a designated lower boundary stratotype locality, lacks a biostratigraphically defined base at a stratotype, and is so sparsely fossiliferous that no biostratigraphic zonation exists.
Long-term problems involving regional definition of the West Gondwanan Lower–Middle Cambrian boundary are resolved. The lowest occurrence of paradoxidid trilobites, the classic index for the base of the Middle Cambrian, is diachronous in West Gondwana and other regions, with the group showing a delayed appearance in Iberia, Sweden, and Bohemia, by comparison with Morocco. Taxonomic revision of Iberian trilobites and new documentation of their ranges in Morocco show that the Iberian terminal “Lower Cambrian” “Bilbilian Stage” (designation abandoned) correlates with the Moroccan upper Banian and lower and middle “Tissafinian” Stages and with the Siberian upper Toyonian (traditionally assigned to the Lower Cambrian in Siberia) and lower Amgan (assigned to the Middle Cambrian in Siberia) Stages. The “Bilbilian” thus includes Middle Cambrian strata in a traditional international concept. Faunas from the base of the Iberian “lowest” Middle Cambrian “Leonian Stage” (designation abandoned) correlate largely into the second trilobite zone of the “Tissafinian” and are now understood to appear above an intra-Middle Cambrian faunal break. This faunal break is still poorly understood and may be an artifact of collection failure immediately above the sparsely fossiliferous, problematical “Valdemiedes event” interval. The base of this “Middle Cambrian”, now termed Celtiberian Series (new designation), in West Gondwana is best defined by the base of the lower Middle Cambrian Agdzian Stage (new designation). The Agdzian includes the “Tissafinian” and overlying lower “Toushamian Stage” designations abandoned) of Morocco, and has its top defined by the base of the middle Middle Cambrian Caesaraugustian Stage, as defined in Spain at the lowest occurrence of Badulesia tenera. The Languedocian, originally defined at the lowest occurrence of Solenopleuropsis (Manublesia) thorali in the southern Montagne Noire of France comprises the third, and terminal stage of the Celtiberian Series. We suggest that the designations “Lower Cambrian” and “Middle Cambrian” be regarded as descriptive and nonchronostratigraphic terms in discussions of the Cambrian.
%B Acta Geologica Polonica %V 54 %P 233-273 %G eng %U https://geojournals.pgi.gov.pl/agp/article/view/10274 %0 Journal Article %J Journal of Paleontology %D 2001 %T Middle Cambrian of Avalonian Massachusetts: Stratigraphy and Correlation of the Braintree Trilobites %A G. Geyer %A E. Landing %K Biostratigraphy %K Braintree Member %K Middle Cambrian %K trilobites %XAlthough Middle Cambrian trilobites of the Braintree Member in eastern Massachusetts were among the first published on in North America, re-examination of this fauna has led to wholesale taxonomic and biostratigraphic re-evaluation. This low diversity fauna now includes at least seven species, with the first report of agnostoids (three poorly preserved taxa) and the ellipsocephalid Kingaspis avalonensis new species. Paradoxides (Acadoparadoxides) harlani Green emend., a senior synonym of P. (A.) haywardi Raymond, allows correlation into the lowest Middle Cambrian elsewhere in Avalon. However, all the polymeroid species are endemic, and this precludes a highly resolved correlation into other Cambrian paleocontinents. A breakdown of provincial barriers in the late Early Cambrian as western Gondwana passed from equatorial to the higher south latitudes of Avalon led to faunal exchanges between these continents. Paradoxides (Acadoparadoxides) and Kingaspis of the Braintree fauna are shared with western Gondwana, while Braintreella and “Agraulos” quadrangularis are closest to genera known from the Spanish, Moroccan, and Perunican (Bohemian) margins of Gondwana.
%B Journal of Paleontology %V 75 %P 116-135 %G eng %U http://dx.doi.org/10.1666/0022-3360(2001)075<0116:MCOAMS>2.0.CO;2 %R 10.1666/0022-3360(2001)075<0116:MCOAMS>2.0.CO;2 %0 Book Section %B Cambrian From the Southern Edge. %D 2000 %T The Cambrian in Israel and Jordan-The Feather Edge of the Mediterranean Region %A G. Geyer %A E. Landing %E G. F. Acenolaza %E Peralta, S. %K Arabo-Nubian Shield %K Cambrian %K Israel %K Jordan %XThe Cambrian of Israel and Jordan belongs to the relatively poorly known regions of Cambrian rocks. The outcrops cover small areas in the southernmost part of Israel, from about 50 km north of Eilat to almost the Red Sea, and areas in the southwestem part of Jordan. The best outcrops are found in the Timna area of Israel, which includes the legendary copper mines of King Solomon, at the eastern shore of the Dead Sea, in the Petra area, and in the Wadi Ram region of Jordan. They belong to a thick blanket of Cambrian through Cretaceous clastics which drapes the northern margin of the Arabo-Nubian Shield and was formerly termed the "Nubian sandstone".
%B Cambrian From the Southern Edge. %S Miscelanea %I Instituto Superior de Correlacion Geologica (INSUGEO), Universidad Nacional de Tucuman %P 98-101 %G eng %U http://insugeo.org.ar/publicaciones/docs/misc-06-24.pdf %0 Book Section %B Morocco '95-The Lower-Middle Cambrian Standard of Western Gondwana %D 1995 %T Arthropod Traces in the Middle Cambrian of Morocco %A G. Geyer %A Heldmaier , W. %A E. Landing %E G. Geyer %E E. Landing %K geology paleontology %B Morocco '95-The Lower-Middle Cambrian Standard of Western Gondwana %S Special Issue %I Beringeria %P 254 %G eng %0 Book Section %B Morocco '95-The Lower-Middle Cambrian Standard of Western Gondwana %D 1995 %T The Cambrian of the Moroccan Atlas Regions %A G. Geyer %A E. Landing %E G. Geyer %E E. Landing %K geology paleontology %B Morocco '95-The Lower-Middle Cambrian Standard of Western Gondwana %S Special Issue %I Beringia %P 7-46 %G eng %0 Book Section %B Morocco '95-The Lower-Middle Cambrian Standard of Western Gondwana %D 1995 %T Faunas and Depositional Environments of the Cambrian of the Moroccan Atlas Regions %A G. Geyer %A E. Landing %A Heldmaier , W. %E G. Geyer %E E. Landing %K geology paleontology %B Morocco '95-The Lower-Middle Cambrian Standard of Western Gondwana %S Special Issue %I Beringeria %P 47-120 %G eng %0 Book %B Special Issue %D 1995 %T MOROCCO '95-The Lower-Middle Cambrian Standard of Gondwana %A G. Geyer %A E. Landing %K geology paleontology %B Special Issue %I Beringria %C , %G eng