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2016 (vol. 16)

A simple technique to establish sequences of datums and to highlight transgressive–regressive cycles
Jean GUEX & Federico GALSTER

 | HTML  | PDF [394 KB]  | DOI : 10.4267/2042/58207

 Abstract:  The relative diachronism of first or last local occurrences (FOs and LOs) of fossil species may highlight transgressive/regressive cycles. A simple technique allowing the extraction of this information by means of the UAgraph program is discussed in the present paper. The technique consists in modifying a usual database of UAgraph by augmenting it with the restricted data concerning only the FOs (or LOs) of the taxa under consideration. The resulting data set combines the information on total ranges and those concerning the FOs and LOs only. Calculating the UAs of such a duplicated database produce a range chart in which we can read the maximal ranges of all the taxa and, in addition, the biochronological dispersion of the FOs and LOs. For a given transgressive/regressive cycle, the UAs defined by the species related to sea level fluctuations migrate with time from distal to proximal sections and inversely. This trend can be detected visually by the means of the UAs reproducibility chart, output of the UAgraph program. In a more general frame, the same holds true for species whose regional dispersion is related to specific conditions and when these conditions migrate in space with time (e.g., water temperatures and diatoms). The above discussion is strictly related to FOs and LOs that for a given section are definitive, however well constrained ephemeral appearances and disappearances can be easily integrated in the database for the same purposes.

Carnets Geol., vol. 16, nº 1, p. 1-16

Online since January 14, 2016


2015 (vol. 15)  

A review of the species of the genus Hemidiadema Agassiz, 1846 (Euechinoidea, Camaradonta, Glyphocyphidae), from the Aptian (Lower Cretaceous) of Spain

 | HTML  | PDF [2,717 KB]  | DOI : 10.4267/2042/58204

 Abstract:   Specimens belonging to the genus Hemidiadema Agassiz, 1846, from Aptian (Lower Cretaceous) strata from the Spanish provinces of Castellón, Tarragona, Barcelona and Teruel –were studied. All specimens of Hemidiadema from these regions cited or described in the literature until now were related to the species Hemidiadema rugosum Agassiz, 1846. Their taxonomic revision – based on historical material and new collecting – demonstrates that these individuals do not belong to the species described by Agassiz, but represent new taxa. Three new species are proposed and described: Hemidiadema batalleri nov. sp., H. malladai nov. sp., and H. forcallensis nov. sp). The species H. rugosum Agassiz, 1846, is known by a single specimen from the Aptian of Castellón. Remarks on the paleoecology and stratigraphic and geographic distributions of these species are given.

Carnets Geol., vol. 15, nº 20, p. 279-330

Online since December 25, 2015

Distribution of Conichnus and Amphorichnus in the Lower Paleozoic of Estonia (Baltica)
Olev VINN, Mark A. WILSON & Ursula TOOM

 | HTML  | PDF [1,137 KB]  | DOI : 10.4267/2042/58180

 Abstract:   Conichnus conicus and Amphorichnus papillatus occur in clay-rich carbonate rocks in the Ordovician of Estonia. Conichnus conicus also occurs in clay-rich carbonates of the early Silurian of Estonia. Lateral adjustment traces are more common in C. conicus than previously recorded. The lack of adjustment traces in Amphorichnus, together with its morphology, does not support synonymy of Conichnus and Amphorichnus. The Conichnus conicus and Amphorichnus papillatus tracemakers preferred shallow water carbonate environments with high clay content. They were rare or did not occur in deeper water muddy environments or where shallow water carbonates accumulated. A high content of volcanic ash in the depositional environment is characteristic of both the Ordovician and Silurian maxima of Conichnus conicus occurrence. C. conicus may have been more common in the temperate seas of Baltica than in the tropics.

Carnets Geol., vol. 15, nº 19, p. 269-278

Online since December 2, 2015

Selected agglutinated larger foraminifera from the Font de les Bagasses unit (early Campanian, southern Pyrenees)
Sergi ALBRICH, Carme BOIX & Esmeralda CAUS

 | HTML  | PDF [5,455 KB]  | DOI : 10.4267/2042/57953

 Abstract:   The Font de les Bagasses marls and marly limestones (Montsec Mountains, NE Spain) host a rich assemblage of larger foraminifera, that was described for the first time in the early 20th Century from the currently submerged locality of Tragó de Noguera (Marginal Mountains). In this paper, a detailed architectural study has been carried out on selected, agglutinated larger foraminifera, which include Choffatella aff. rugoretis Gendrot, Hemicyclammina chalmasi (Schlumberger), Cuneolina conica Orbigny, Cuneolina cylindrica Henson, and Dictyopsella kiliani Munier-Chalmas. Moreover, it presents their biostratigraphic range and the range of the associated porcellaneous and lamellar-perforate foraminifera in the study area. The assemblage is Early Campanian in age.

Carnets Geol., vol. 15, nº 18, p. 245-267

Online since November 18, 2015

Tremichnus in crinoid pluricolumnals from the Silurian of western Estonia (Baltica)
Olev VINN, Mark A. WILSON, William I. AUSICH & Ursula TOOM

 | HTML  | PDF [644 KB]  | DOI : 10.4267/2042/57951

 Abstract:   Quelques petites cavités attribuées à Tremichnus ont été trouvées dans des crinoïdes provenant du Silurien d'Estonie. Ce Tremichnus rhuddanien est le symbiote le plus ancien observé dans des segments de tiges de crinoïdes du bouclier balte. Ces cavités correspondent vraisemblablement à des habitats d'organismes inconnus. Tremichnus a eu un impact négatif sur le crinoïde hôte comme en attestent les renflements des tiges. Tremichnus est moins fréquent dans le Silurien d'Estonie que des traces semblables dans le Silurien du Gotland voisin. L'aspect le plus significatif de cette étude est la rareté de cette interaction dans ces échantillons à la différence de la plupart des échantillons du même âge provenant d'autres localités. Ces structures ont une répartition très irrégulière.

Carnets Geol., vol. 15, nº 17, p. 239-243

Online since November 18, 2015

Scientific death-knell against databases? Errors induced by database manipulations and its consequences
Christian C. EMIG, Maria Aleksandra BITNER & Fernando ÁLVAREZ

 | HTML  | PDF [107 KB]  | DOI : 10.4267/2042/57949

 Abstract:   References to Terebratulina caputserpentis attributing its authorship to Zbyszewski, 1957, not to Linnæus, 1767, have been found in three recent publications, in the collections of the Muséum National d'Histoire naturelle de Paris and in several online databases. The use in these databases seems to have arisen from WoRMS (World Register of Marine Species), specifically from WBD (World Brachiopoda Database) of which the three authors of this paper are the editors (authors). The page concerning T. caputserpentis (Linnæus, 1767) has been modified by WoRMS staff without the knowledge of these editors (authors).
The decrease of the specialists in systematics and their replacement by IT specialists question the scientific reliability of the online databases as well as the specimen labelling in museums. The absence of scientific rigour becomes their Achilles' heel. Several other cases of errors are quoted and developed. In spite of applications to the staff of databases in biodiversity, the situation continued degrading so much so that today these bases are reached by the Peter principle and can no longer be used for scientific requirements, except if verifying all the desired data.

Carnets Geol., vol. 15, nº 16, p. 231-238

Online since November 11, 2015

New fossiliferous sites with Barremian Charophyta in the "Grès du Liban" auct. (Lebanon), with a critical perspective regarding the nature of Munieria Deecke, 1883
Bruno GRANIER, Dany AZAR, Sibelle MAKSOUD, Raymond GÈZE & Roland HABCHI

 | HTML  | PDF [5,904 KB]  | DOI : 10.4267/2042/57947

 Abstract:   The "Grès du Liban" auct. is the thick basal unit of the Lower Cretaceous series in Lebanon. There are two key levels in this dominantly siliciclastic unit: the "Banc de Mréjatt" and the "Calcaire à pisolithes", the latter of which includes limestones and marls with Charophyta. The rich charophyte assemblage described by Grambast and Lorch (1968) from a site near Jezzine is Barremian (possibly Early Barremian) in age, not Bedoulian as previously stated. Besides gyrogonites and utricles, charophyte thalli are rather common; they are ascribed to two organ genera, Munieria Deecke, 1883, and Charaxis Harris, 1939. Based on topotypic material (from the Pia Collection), Munieria baconica Deecke, 1883, the type-species of the genus, is reassessed. In addition, the species Clypeina parvula Carozzi, 1946, is transferred to the revised genus Munieria, and a new species of Charaxis is described.

Carnets Geol., vol. 15, nº 15, p. 199-229

Online since November 11, 2015

Palaeoenviromental and palaeogeographical traits on deep-water ostracod assemblages from the Lower Pleistocene sediments along the Ionian side of Mount Etna (Sicily, Italy)
Francesco SCIUTO

 | HTML  | PDF [2,013 KB]  | DOI : 10.4267/2042/57945

 Abstract:   The ostracod associations of the Lower Pleistocene sedimentary succession cropping out at Serra San Biagio (Catania, Sicily NE) have been investigated. The ostracod fauna from nine samples is poorly diversified but well-preserved: A total of forty taxa of ostracods have been identified, thirty-three at specific level and seven at genus level or doubtful species. Thirty species are considered as constituents of the in situ original assemblages. The associations consist almost exclusively of bathyal taxa such as Bythocypris obtusata (Sars), Anchistrocheles antemacella Maddocks, Henryhowella ex H. hirta (Costa) group, Quasibuntonia radiatopora (Seguenza), Retibythere (Bathybythere) scaberrima (Brady) and Bathycythere vansraateni Sissingh. Also the Krithe group is well-represented with Krithe compressa (Seguenza) and K. pernoides (Bornemann). Almost all species, some, particularly interesting from the palaeoecological and palaeogeographical point of view, have been here described, illustrated and commented on, including a species belonging to the genus Cytherella Jones, 1849, found in all samples of the section, which is here proposed as new.

Carnets Geol., vol. 15, nº 14, p. 179-197

Online since November 11, 2015

Review of some Aptian ammonites collected by Gaston Astre in Lleida Province, Catalonia, Spain

 | HTML  | PDF [934 KB]  | DOI : 10.4267/2042/56911

 Abstract:   We study the three best preserved ammonites collected by Astre in 1924-1925 in Lleida Province, Catalonia, Spain, in order to assess their taxonomic assignment. We also include images of these ammonoids since they were not illustrated in Astre's original 1934 work. This taxonomic review allows us to identify these lower Aptian ammonites as Pseudohaploceras liptoviense, Deshayesites sp. and Dufrenoyia sp.

Carnets Geol., vol. 15, nº 13, p. 173-178

Online since August 6, 2015

Sequence stratigraphic architecture of marine to fluvial deposits across a passive margin (Cenomanian, Atlantic margin, Morocco, Agadir transect)
Badre ESSAFRAOUI, Serge FERRY, Danièle GROSHÉNY, Nourrisaid IÇAME, Hassan EL AOULI, Moussa MASROUR, Luc G. BULOT, Yves GÉRAUD & Mohamed AOUTEM

 | HTML  | PDF [24,372 KB]  | DOI : 10.4267/2042/56909

 Abstract:   Seven sections, covering the upper Albian to lowermost Turonian, have been correlated from full-marine to continental-dominated deposits across a passive margin, along a transect 425 km long, from the present-day Atlantic coast to the "Pre-African Trough" between the Anti-Atlas and the High-Atlas. The thickness of the Cenomanian succession changes from around 500 metres in the fully marine sections to 250 metres in mostly continental facies in the western High-Atlas, about 150 km updip, to a few tens of metres in the Bou Tazoult area. The strata thicken again eastwards into the Pre-African Trough where they can be traced without major facies changes to the Kem Kem embayment and to the Bechar area in Algeria. Over all this eastern area, continental facies are overlain by the fully-marine shallow-water deposits of the Cenomanian-Turonian boundary interval.
A first major conclusion is that fluvial aggradation in high-frequency transgressive-regressive sequences is coeval with the seaward-shift of the shoreline, in accordance with the genetic sequence stratigraphic model of Galloway (1989). Both the flatness of the depositional profile and the corresponding very low energy of the marine environment during the transgressions account for the blanket of red continental clays on top of marine facies in updip depositional sequences, which is then preserved under the marine transgressive surface of the next sequence.
A second major conclusion is that the high-frequency transgressive-regressive (T-R) sequences do not look like classical parasequences bounded by transgression surfaces. They usually exhibit a surface created by a sea-level fall within the regressive half-cycle. This is interpreted in the following way: regressions did not operate through a regular seaward-shift of the shoreline, but through stepped sea-level falls. The very low slope of the depositional ramp is thought to have enhanced the sequence stratigraphic record of such stepped regressions. Short-term, high-frequency sequences are organized into medium-frequency T-R sequences (seven in the Cenomanian) which show an overall aggrading and slowly retrograding pattern along the whole transect.
Comparisons with other basins show that medium-frequency sequences do not fit the third-order depositional sequences described elsewhere, casting doubts about a eustatic mechanism for their deposition.

Carnets Geol., vol. 15, nº 12, p. 137-172

Online since August 6, 2015

End of a modern geological myth: there are no rudists in Brazil! Paleobiogeographic implications

 | HTML  | PDF [1,631 KB]  | DOI : 10.4267/2042/56880

 Abstract:   Out of the few records of rudists from the Cretaceous strata of the South Atlantic coastal basins only two refer to Brazilian localities. However, petrographic analyses demonstrate that these shells should be assigned to Ostreids or to Pycnodontids rather than to Rudistids. More specifically, the domain considered herein, north of the Río Grande Rise - Walvis Ridge barrier, was part of the warm-water "tropical" realm, but it was not part of the Mesogean domain because both Rudistids and Orbitolinas are missing. In addition, the scarcity of corals leads us to ascribe the taphonomic assemblage to the Chloralgal facies. Neither generalized hypersalinity or extreme sea-water temperatures seem to account for these biotic peculiarities. Instead, our alternative hypothesis favors the driving role played by oceanic circulation in the dispersal of the benthic organisms.

Carnets Geol., vol. 15, nº 11, p. 123-136

Online since July 14, 2015

Facies, biostratigraphy, diagenesis, and depositional environments of Lower Cretaceous strata, Sierra San José section, Sonora (Mexico)
Jayagopal MADHAVARAJU, Robert W. SCOTT, Yong Il LEE, Kunjukrishnan Sathy BINCY, Carlos M. GONZÁLEZ-LEÓN & Sooriamuthu RAMASAMY

 | HTML  | PDF [1,401 KB]  | DOI : 10.4267/2042/56879

 Abstract:   We used petrofacies analysis, carbon, oxygen and strontium isotope data to interpret the isotopic variations in the carbonate rocks of the Mural Formation of Sonora (Sierra San José section), Mexico. The petrographic study reveals a range of lithofacies from wackestone to packstone. The analyzed limestones show significant negative δ18O values (-18.6 to -10.9 VPDB) and δ13C values ranging from negative to positive (-2.6 to +2.5‰ VPDB). The absence of correlation between δ13C and δ18O values suggests a primary marine origin for the δ13C values of limestones from the Sierra San José section. The limestones have large variations in 87Sr/86Sr values (0.707479 to 0.708790). Higher 87Sr/86Sr ratios in various levels of the studied section suggest that most of the sediments were derived from the Proterozoic basement of the Caborca block during Early Cretaceous time. A decrease in 87Sr/86Sr ratios at certain levels indicates an influx of lesser amounts of radiogenic Sr that could have been caused by contribution of sediments from the Triassic and Jurassic volcanic rocks.

Carnets Geol., vol. 15, nº 10, p. 103-122

Online since July 14, 2015

Cambrian fossils from the Barrandian area (Czech Republic) stored in the Musée d'Histoire Naturelle de Lille
Oldřich FATKA, Petr BUDIL, Catherine CRÔNIER, Jessie CUVELIER, Lukáš LAIBL, Thierry OUDOIRE, Marika POLECHOVÁ & Lucie FATKOVÁ

 | HTML  | PDF [1,415 KB]  | DOI : 10.4267/2042/56878

 Abstract:   A complete list of fossils originating from the Cambrian of the Barrandian area and housed in the Musée d'Histoire Naturelle de Lille is compiled. The collection includes two agnostids, ten trilobites, one brachiopod and one echinoderm species, all collected at ten outcrops in the Buchava Formation of the Skryje-Týřovice Basin and most probably also at two outcrops in the Jince Formation of the Příbram-Jince Basin. A large part of the material was collected by Prof. Charles Barrois and Dr. Louis Dollé (both University of Lille) during the excursion organised before the Ninth International Geological Congress in Vienna in 1903. Other, poorly documented specimens were purchased from the enterprise Krantz towards the end of the 19th century and in the first years of 20th century. The geographic position and stratigraphy of outcrops, from which the material originates, are briefly discussed.

Carnets Geol., vol. 15, nº 9, p. 89-101

Online since July 14, 2015

Lower Valanginian ammonite biostratigraphy in the Subbetic Domain (Betic Cordillera, southeastern Spain)

 | HTML  | PDF [1,459 KB]  | DOI : 10.4267/2042/56745

 Abstract:   A new zonation for the lower Valanginian in the Betic Cordillera is presented. It is based on the study of 16 sections located near Caravaca and Cehegín (Region of Murcia). From bottom to top, the following interval zones, defined by the first appearance of the index-species, are distinguished:
● "Thurmanniceras" pertransiens Zone, which can be subdivided into two subzones, a lower "Th." pertransiens Subzone and an upper Vergoliceras salinarium Subzone. The latter is characterized by the disappearance of Olcostephanus drumensis and the appearance of Luppovella superba.
Neocomites neocomiensiformis Zone, also with two subzones, the Baronnites hirsutus Subzone below (characterized by the appearance of "Busnardoites" subcampylotoxus and Olcostephanus guebhardi) and the Valanginites dolioliformis Subzone above ("Busnardoites" campylotoxus is restricted to this subzone).
Karakaschiceras inostranzewi Zone, subdivided as well into two subzones, a lower Karakaschiceras inostranzewi Subzone and an upper Saynoceras contestanum Subzone.
The assemblages characterizing each of these biozones can be recognized throughout the Mediterranean region.

Carnets Geol., vol. 15, nº 8, p. 71-88

Online since June 11, 2015

Some encrusted hardgrounds from the Ordovician of Estonia (Baltica)
Olev VINN & Ursula TOOM

 | HTML  | PDF [344 KB]  | DOI : 10.4267/2042/56744

 Abstract:   The Ordovician hardground faunas of Estonia are not diverse. They include echinoderm holdfasts (i.e., eocrinoids and crinoids), edrioasteroids, bryozoans (both hemispherical trepostomes and stalked ptilodictyids) and cornulitids. The earliest hardground faunas appeared in the Dapingian (i.e., bryozoans and echinoderms). The Estonian hardground faunas are less diverse than the North American ones. North American hardgrounds seem to be more heavily encrusted than the Estonian ones. These differences may be due to the paleogeographic distances, different climates and different sedimentation environments of the paleocontinents.

Carnets Geol., vol. 15, nº 7, p. 63-70

Online since June 11, 2015

MayLib - a textfile-based bibliographic database for geosciences and a list of references on Devonian matters
Andreas MAY

 | HTML  | PDF [420 KB]  | DOI : 10.4267/2042/56481

 Abstract:  Scientists need to manage their own collections of bibliographic data as well as exchange these data easily with colleagues. One solution for this need is MayLib, a bibliographic database that runs on many different operating systems and does not require pre-installation of any software. MayLib is a very small, efficient and comprehensive JAVA program that handles references to publications in any Unicode-compatible language. It is user-friendly and not only contains the basic functions of a bibliographic database, but also has some advanced features. Using MayLib the author has been able to create a list of references, which contains 500 periodicals and 4206 literature references. Of these 4206 references 3191 deal with Devonian matters and 1594 references deal with corals.

Carnets Geol., vol. 15, nº 6, p. 59-62

Online since March 9, 2015

New faunistic data on the Pleistocene environmental evolution of the south-western edge of the Hyblean Plateau (SE Sicily)
Francesco SCIUTO, Antonietta ROSSO, Rossana SANFILIPPO & Rossana MANISCALCO

 | HTML  | PDF [2,810 KB]  | DOI : 10.4267/2042/56401

 Abstract:  Faunistic associations of the Lower Pleistocene sediments, out-cropping at Cartiera Molino along the true right bank of the Ippari River (Vittoria, SE Sicily), have been investigated. This study integrates data obtained from the analysis of ostracods, foraminifers, bryozoans and serpulids found within a six metre thick sedimentary section. This multiproxy approach allowed us to reconstruct the palaeoenvironmental evolution of this south-western sector of the Hyblean Plateau (Comiso-Vittoria area) from fluvially-influenced shallow marine settings, recorded in the lower portion of the succession, to progressively shallower, transitional and brackish environments, testified in mid levels, up to freshwater environments at the top of the section.

Carnets Geol., vol. 15, nº 5, p. 41-57

Online since February 28, 2015

A reassessment of the validity and affinities of Belemnites sulcatus Miller, 1826, Belemnopsis Edwards in Gray, 1849, and Belemnopsis Bayle, 1878

 | HTML  | PDF [172 KB]  | DOI : 10.4267/2042/56399

 Abstract:  A reinvestigation of the validity of the belemnite genus Belemnopsis Bayle is undertaken, together with a survey of the early history of the usage of the names Belemnites sulcatus, Belemnopsis Bayle and Belemnopsis Edwards. Belemnites sulcatus Miller has been variously equated with either Belemnites apiciconus Blainville or with the group of belemnites including Belemnites Altdorfensis Blainville and B. Beaumontianus Orbigny. Riegraf (and not Phillips) subsequently designated a lectotype which may be valid and, in case it is not, is validated here. The species concept for Belemnites sulcatus, as based on this lectotype, places it in the genus Holcobeloides Gustomesov. Belemnopsis Edwards has date priority over Belemnopsis Bayle, but must be interpreted as an "incorrect original spelling" and, therefore, does not enter into homonymy according to the ICZN; Belemnopsis Bayle is thus a valid genus. Douvillé subsequently nominated Belemnites sulcatus, which was figured as Belemnopsis sulcata by Bayle, and therefore is a valid designation because this species is amongst the original species included in Belemnopsis by Bayle. One of Bayle's figures of Belemnopsis sulcata agrees with Belemnites apiciconus Blainville, but does not agree with Belemnites sulcatus as defined by its lectotype; as such this is a case of misidentified type species. Belemnites apiciconus Blainville, the species involved in the misidentification, is therefore designated type species of Belemnopsis Bayle here and validated by citing the ICZN. The actions taken here maintain nomenclature at the genus, family and suborder level in respect to the names Belemnopsis and Belemnosis and serve to stabilize the complicated nomenclature issues related to these taxa.

Carnets Geol., vol. 15, nº 4, p. 31-39

Online since February 28, 2015

Earliest Aptian Caprinidae (Bivalvia, Hippuritida) from Lebanon
Jean-Pierre MASSE, Sibelle MAKSOUD, Mukerrem FENERCI-MASSE, Bruno GRANIER & Dany AZAR

 | HTML  | PDF [1,585 KB]  | DOI : 10.4267/2042/56397

 Abstract:  The presence in Lebanon of Offneria murgensis and Offneria nicolinae, two characteristic components of the Early Aptian Arabo-African rudist faunas, fills a distributional gap of the corresponding assemblage between the Arabic and African occurrences, on the one hand, and the Apulian occurrences, on the other hand. This fauna bears out the palaeogeographic placement of Lebanon on the southern Mediterranean Tethys margin established by palaeostructural reconstructions. The associated micropaleontological elements suggest an earliest Aptian age (early Bedoulian) for the Offneria murgensis - O. nicolinae assemblage found in the "Falaise de Blanche" stratigraphic interval, instead of a late Early Aptian age as proposed for most of the peri-Adriatic and Middle East occurrences recognized so far. These caprinid specimens are characterized by relatively modest sizes, moreover other rudists commonly part of the assemblage are lacking. The dominance of caprinids in the study area suggests a distal platform setting, i.e., close proximity to the platform edge.

Carnets Geol., vol. 15, nº 3, p. 21-30

Online since February 15, 2015

Simple and practical techniques to manage small databases, illustrated by a case study: bibliographic data from the "Fossil Cnidaria & Porifera" newsletter (1972-2010)
Katarzyna ZALECKA, Tomasz WRZOŁEK & Bruno GRANIER

 | HTML  | PDF [342 KB]  | DOI : 10.4267/2042/56249

 Abstract:  Small databases, i.e., with less than 15,000 entries, are sometimes handled using inappropriate, complex, and often expensive data management systems. We present and briefly discuss a few types of proprietary and open-source, relational and non-relational, server-based versus portable databases and specific tools to handle the latter. With a collection of nearly 7,000 bibliographic notes during its 40-year history "Fossil Cnidaria & Porifera (FC&P)", the newsletter of the "International Association for Study of Fossil Cnidaria and Porifera", was chosen as a case study. The analysis of the temporal trends in the FC&P bibliographic database shows a decrease over the years in the number of publications effectively reported in FC&P. Almost all relevant papers for the decade 1981-1990 are reported, but this good coverage ratio falls down to less than 50% after 2000; accordingly, the concern about the data representativeness is addressed in our interpretation. Besides the classical database management systems and spreadsheet software, which were originally used with the FC&P case study, we present two discrete, open-source, flat and portable options where data can be displayed using any widely available Internet browser, and that are suitable to handle most small databases (XML or JS files) as documented herein.

Carnets Geol., vol. 15, nº 2, p. 13-19

Online since January 14, 2015

Lower Aptian ammonites of the Sierra de Parras, Coahuila State, northern Mexico

 | HTML  | PDF [2,356 KB]  | DOI : 10.4267/2042/56250

 Abstract:  We report an interesting Aptian ammonite record from the La Peña Formation in the Sierra de Parras, Coahuila State. This assemblage is analyzed from a paleoecological perspective. It contains the first reported occurrence of a macroconch of Dufrenoyia from Mexico, and the largest known specimen of  'Gargasiceras' adkinsi. Such an assemblage yielding large ammonites is unusual in deposits of this age in Mexico. To properly document this ammonite record, we review 'Gargasiceras' adkinsi, formerly misidentified as Rhytidoplites robertsi, and allied taxa. From our analysis, we conclude that 'Gargasiceras' adkinsi exhibits strong intraspecific variability. We also analyze in detail the differences that exist between 'Gargasiceras' adkinsi and Rhytidoplites robertsi, and emend the concept of the genus Rhytidoplites. These revisions are important from a biostratigraphic point of view since 'Gargasiceras' adkinsi is an index species for the lower Aptian ammonite zonation of Mexico.

Carnets Geol., vol. 15, nº 1, p. 1-11

Online since January 14, 2015

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