323 research outputs found
Pal Grande Formation
No full textThe Pal Grande Formation consists mainly of gray mudstone and wackestone rich in fossils. The original bedding is often concealed by pressure solution and/or burrowing giving to the limestone a characteristic pseudo-nodular look. The reddish colour, when present, is usually limited to the lower part of the formation. At places, in the basal part of the formation, interlayered cm to dm calciruditic and calcarenitic (grainstone) intervals are present, as well as ruditic (intraclast breccia) levels. The ruditic beds can reach thickness of 1-2 m. Black shale, intepreted as equivalent to the Hangenberg Shale (Hangenberg Event) are present only at two localities (Kronhof Graben and Plan di Zermula) (Perri & Spalletta, 2001)
Biodiversità e litofacies ai limiti Frasniano–Famenniano e Permiano–Triassico in Alpi Meridionali: indagine multidisciplinare su due dei “Cinque Grandi”
No full textLe estinzioni al tetto del Frasniano e del Permiano sono considerate due dei “Cinque grandi” eventi di estinzione globale del Fanerozoico. La ricerca verterà su analisi paleontologiche associate ad analisi sedimentologiche e geochimiche su sezioni delle Alpi Meridionali in successioni comprendenti i limiti Frasniano–Famenniano (Fr–Fm) e Permiano–Triassico (P–T), caratterizzati da una drastica riduzione della biodiversità globale.
Lo studio, già intrapreso da alcuni anni dal gruppo di ricerca, sarà approfondito ed esteso a nuove sezioni. I dati paleontologici finora basati quasi esclusivamente sui conodonti saranno integrati da quelli di altri gruppi fossili. Sarà così possibile valutare la variazione della biodiversità prima, durante e dopo gli eventi di estinzione, al variare delle condizioni ambientali dedotte dall’analisi delle litofacies, il cui parametro più importante, finora poco valutato, è la stima dell’entità dei rimaneggiamenti. Dati isotopici e paleomagnetici associati a quelli paleontologici e sedimentologici forniranno informazioni sulla fluttuazione dei parametri ambientali.
A) Sulle problematiche del limite Fr–Fm è comparsa nell’ultimo decennio un’abbondante letteratura che non comprende dati inerenti le Alpi Meridionali. La lacuna potrà essere colmata dalla recente individuazione di due sezioni carbonatiche delle Alpi Carniche che, per mezzo di una analisi biostratigrafica a conodonti preliminare, hanno consentito di identificare l’esatta posizione del limite Fr–Fm, definito dalla prima comparsa di Palmatolepis triangularis conodonte marker del limite. L’estinzione al tetto del Frasniano si realizza in due eventi (Lower e Upper Kellwasser events) molto ravvicinati nel tempo (c.a 500.000 anni) che spesso corrispondono a livelli di shales neri. In entrambe le sezioni Pramosio A (Pizzo Timau) e Freikofel T (Monte Freikofel) l’intervallo critico, che in altre aree è caratterizzato dalla presenza degli shales neri, è costituito da carbonati bioturbati di mare basso. Lo studio sedimentologico sulla sezione Pramosio A è stato realizzato su una campionatura in continuo, per mezzo di un carotatore portatile, al fine di ottenere una successione inintettotta di sezioni sottili e lastre lucidate. L’analisi così dettagliata ha permesso il riconoscimento di numerose sequenze deposizionali cicliche, alcune di spessore centimetrico-decimetrico, e la calibratura preliminare dei dati sedimentologici con quelli biostratigrafici a conodonti.
Nell’ambito della ricerca si prevede una campionatura di maggior dettaglio della sezione Pramosio A e l’estensione dell’indagine sia sedimentologica che paleontologica alla sezione Freikofel T che nella parte alta è caratterizzata da facies carbonatiche meno prossimali con intervalli nodulari rossastri intercalati a livelli di brecce con clasti di derivazione anche peritidale.
B) La successione Permiano–Triassico delle Alpi Meridionali rappresenta il margine occidentale della Paleotetide a latitudine equatoriale. E’ costituita dalle formazioni a Bellerophon e di Werfen che presentano, a livello regionale, due unconformity, una in corrispondenza del limite formazionale e l’altra subito sotto. La sezione di Bulla (Bolzano) si è rivelata eccellente sia per lo studio sedimentologico che biostratigrafico essendo l’unica sezione in Italia dove è stato possibile individuare il limite P–T sulla base della prima comparsa, all’interno della sequenza evolutiva praeparvus–parvus–isarcica, del conodonte Hindeodus parvus, marker che definisce la base del Mesozoico. Si prevede di integrare i dati paleontologici sui conodonti con quelli inerenti foraminiferi, brachiopodi, lamellibranchi, gasteropodi e pollini al fine di una completa valutazione della variazione della biodiversità. Nella sezione Bulla verranno effettuate analisi isotopiche da correlare a quelle paleomagnetiche già disponibili e campionature sedimentologiche in continuo, realizzate con carotatore. Questo tipo di analisi sedimentolo..
Conodont evolution and biostratigraphy: aligning the Permian–Triassic boundary sequences of the Southern Alps
No full textMillennial physical events and the end-Permian mass mortality in the western Palaeotethys: timing and primary causes.
No full textThis chapter focuses on the nature and pattern of four transgressive–regressive
depositional cycles (C1–C4) across the Permian–Triassic Boundary (PTB) in the
Dolomites, on their timing and on the possible causal relationships with four massmortality
events (E0–E3), which, considered together, constitute the end-Permian
extinction event in the western Palaeotethys. The duration of the investigated interval
is ca. 200 ky; the duration of each cycle ranged from less than 20 ky to ca. 100 ky; and
the magnitude of the sea level changes ranged from 5 to 15 m. Each mass-mortality
event affecting the shallow marine environments of the western Palaeotethys corresponds
with a regressive phase lasting a few millennia. The oldest mortality event
(E0) at the top of Cycle 1 (i.e., the top of the Ostracod Unit) in the Southern Alps
is aligned with the regressive Bed 24e of the Meishan D section in the eastern
Palaeotethys; it is usually considered the actual end-Permian extinction event. The
same cooling/fall-stand has been identified in various sites along the shallow-marine
Gondwana margin. In the Southern Alps, E0 is mostly masked by stressed conditions
typical of the regional carbonate tidal flat. During the following transgression
and high-stand periods of Cycle 2 (i.e., Bulla Member), the shallow marine environment
became re-populated by ca. 200 species referred to ca. 30 genera. At the top of
Cycle 2, the sea level fell 10 m or less in a few millennia; it started the most devastating
mass-mortality event (E1) in the Southern Alps. This mortality event lasted less
than 20 millennia; it continued briefly during the trangressive phase of the following
Cycle 3—which brackets the Bellerophon-Werfen formational boundary (BWB).
This interval, aligned with Beds 26–27a at Meishan in the eastern Palaeotethys, was
deposited in a deeper and distal environment. About 90% of the marine skeletal
biomass disappeared at the end of E1. The acme of mortality event, E1, corresponded
with a submarine chemical-corrosion event, followed locally by subaerial exposure
and pedogenesis. The mass-mortality event on land slightly predates—or is nearly
coeval—with the mass-mortality event in shallow marine environments. The intensity
of submarine corrosion became almost imperceptible at the foreshore–offshore boundary.
The sea level rose ca. 15 m during Cycle 3 when the shallow marine environment,
mostly over-saturated in carbonate but punctuated by short periods of vadose or submarine
dissolution, transgressed rapidly more than 40km inland over the corroded bedrock,
depositing oolite shoals and microbialite. The subsequent mortality events E2 and E3
are obviously of less intensity. E2, ca. 20 ky after E1, corresponds to a regressive interval
associated with the first appearance of Hindeodus parvus (i.e., the Permian–Triassic
Boundary). It seems to be the acme of colonisation of the shallow sea floor by cyanobacteria
(stromatolites). E3, ca. 10 ky after the Permian–Triassic Boundary, corresponds
to the last occurrence of Permian-type red algae in the Dolomites area. Whereas the
end of E3 is gradual in the shoreface, it appears to have been abrupt in the lower foreshore,
probably because of general conditions of less-ventilated and suboxic conditions.
We hypothesise that a few local palaeo-environmental factors (e.g., distance of stressing
factors from the source area, the pattern of atmospheric and marine palaeocurrents,
and reduction of the shallow coastal area due to retreat of the coastline) concurred to
modulate the intensity and duration of mortality events in space and time. Data suggest
that increased warming was of primary importance in controlling the mortality tail but
doesn’t allow us to confirm or deny other local or general concurrent causes, such as
up-welling of anoxic oceanic waters from the Palaeotethys. We interpret the cause of
the mass-mortality events in the Dolomites area as having been a composite “top-down”
mechanism with acid-rain events devastating the Permian-type life on continental and,
subsequently, in shallow marine environments during millennial periods of cooling and
regression of the Bellerophon sea. The ultimate causal factor was, very probably, large
atmospheric perturbations connected with volcanism. Most of the sparse surviving biota
disappeared immediately after the beginning of the following transgression—because
of rapid global warming produced by greenhouse conditions, with only minor, repeated,
episodes of acid rains. These stressed conditions contributed to inhibiting recovery of the
long and efficient shallow-marine food chain. Because the magnitude of mass-mortality
event E0 in the Dolomites and in much of the Gondwana margin is appreciably lower
than the coeval one in Meishan, the first may have acted as refugia. Mass-mortality event
E1 affected the shallow-marine western Palaeotethys for only a few millennia after E0.
In the eastern Palaeotethys, coeval Beds 26–27a of Meishan were deposited from lower
foreshore to marine shelf, lacking any clear record of anoxic conditions. It is the same
for the coeval short-term parasequences in many sites along the Gondwana margin. We
interpret the different magnitude of extinction on the shelves as due to different levels
of temperature and excessive carbon dioxide (pCO2) in the seawater. The rapid
demise of taxa (occurring concordantly with the diachronous major mortality events)
caused local severing of food chains, mostly of small suspension feeders, resulting in the
“Lilliput” faunas (sensu Twitchett 2005) of event E2 in the Dolomites. This aligns with
Beds 27c–d at Meishan—these beds were deposited in the lower foreshore and marine
shelf environments under suboxic to dysoxic bottom conditions. It seems unlikely that
the disappearance of red algae in the western Palaeotethys was connected with dysoxic
conditions; increased temperature seems a more likely factor. Doubtless a medley of
different mechanisms, including rapid fluctuations in marine salinity, operated variously
as regards time and space and produced the end-Permian extinction—occurring over a
time span of less than 100 ky
Pander Society Newsletter
No full textChief Panderer’s Remarks
Welcome to the 2012 edition of the Pander Society Newsletter, my third attempt at providing news and a list of conodont publications for the past year! We have again enjoyed formal and informal meetings of the Society. Please let me know about even the smallest ‘get-togethers’. Also, do send me copies of any relevant documents and photographs for addition to the Archive (historical record) that continues to build up. Conodont research has continued to flourish but there were 88 non-responses to my request for brief reports on research activities. I hope this does not reflect a decline in active membership. All contributions were very welcome, but we would like to have information (even including reminiscences) from those who feel their achievement may have been minimal.
I am aware that we are overwhelmed by increasing teaching commitments, and by pressing demands from other groups to which we belong. But we are also Panderers, and I hope proud to belong to our Society, becoming more active, communicative and ready to exchange information, using Con-nexus, and the Pander Society's mailing list as well as the newsletter. Even a small contribution may help many of the conodont community to be better informed and, above all, united. I am happy to report that Con-nexus seems to have taken on a new life. It is a wonderful medium for airing ideas.
During the many years I have been a member of the Pander Society I have felt that, overall, our membership has been decreasing. There are doubtless many reasons for this. I remain enthusiastic and optimistic and hope you have similar feelings, even when financial support for palaeontological research may be declining. Enthusiasm and a sense of belonging to a group develop when you have the opportunity to meet up with colleagues. Because our average age has been increasing, we especially welcome new recruits. The appeal I sent earlier this year proved fruitful―it resulted in 20 new Pander Society colleagues. I thank those who have urged partners in work, as well as masters and PhD students to join. I also thank all those who sent changes of addresses and e-mails of colleagues I could not contact for a long time, but that I was reluctant to remove from the mailing list. Even such simple collaboration helps keep the group together.
Computer hackers have continued to be very active during the past year and have caused many colleagues to change their e-mail addresses. Please inform me when this occurs.
A major blow to conodontology was the passing of Charles Collinson on 25 November ― see Obituary by Gilbert Klapper. The prospect of an informal meeting of the Society in association with the International Geological Congress in Brisbane on 5–15 August 2012 faded away; there were too few starters. The only official Pander Society meeting was one held in Dayton, Ohio, in association with the Annual Meeting of the North-Central Section of the Geological Society of America in April 2012. Non-official meetings occurred in association with International Subcommissions on Stratigraphy, IGCP 591 and IGCP 596 projects, and the meeting organised in memory of Tim Tozer during the Canadian Paleontology Conference in Vancouver, last August.
Large-scale scientific monographs continue becoming harder to get published; ‘salami’ publication is flourishing. Despite little notice being taken conference abstracts, do not hesitate to send citations for these ephemera for incorporation into our consolidated list of publications.
Thank you for sending in your contributions; it is always a pleasure to interact with anyone enamoured of conodonts! Thanks also to Suzanna Garcia-Lopez, John Repetsky and Wang Cheng-Yuan for deliberating on nominations for the Society's medals. I am also very grateful to webmaster Mark Purnell (Leicester) who volunteered a few years ago to load the newsletter onto the web. I am always grateful to Myriam Matteucci, an old friend from university days and even earlier, and to Claudia Spalletta for helping Myriam and me get this newsletter down the ‘chute. Special thanks go to Myriam for enormous help in stitching together the entire bibliography and providing the version in EndNote of this year’s entries, now available on the Pander Society website. Thanks also to John Talent who ran his eye over the newsletter and, as he says, “eliminated a few lumpy areas”.
I remind you that during ICOS-3 in Argentina in July 2013, where I hope to meet most of you, my term as Chief Panderer will expire. A new Chief Panderer will need to be appointed. Please reply when you are asked for nominations.
Best wishes to all of you and, I hope, brilliant results from your research that I look forward to reporting in my final newsletter!
Maria Cristina Perri, Chief Pandere
Città e paesaggio: continuare Chiaramonte Gulfi
No full textChiaramonte Gulfi è ancora paesaggio, senza bisogno di particolari aggettivazioni, se si pensa alla definizione di questo termine, spesso abusato, che ne ha dato Rosario Assunto quando ha parlato di paesaggio come di uno spazio aperto, limitato, rappresentazione dell’infinito nel finito. Ma più ancora di questo sono le due situazioni correlative delle quali parla Assunto quando dalla dimensione universale del paesaggio approda alla dimensione locale della città addentrandosi idealmente in strade e piazze, che sembrano essere state ispirate dai luoghi di Chiaramonte Gulfi: in una strada o in una piazza può esservi paesaggio così come può, una via cittadina essere nel paesaggio
Il Bastione
No full textIl progetto del laboratorio da noi coordinato si inscrive nella più ampia proposta delineata con i laboratori tenuti da Carlo Moccia e Marco Mannino. Lo sforzo è stato quello – nel rispondere in maniera integrata ai temi proposti – di definire un complessivo ragionamento e una strategia urbana sulla forma della città di Chiaromonte, sul suo rapporto con la geografia e sulla possibilità di ridefinirne un carattere unitario. In altri termini vi è stato il tentativo condiviso, ma anche l’ambizione, di individuare all’interno del sistema morfologico della palazzata, assunta come nuova possibile “cinta muraria”, alcuni temi in grado di nominarsi come temi compositivi: la torre, il bastione e lo spalto. Nel progetto da noi sviluppato, il centro geometrico della composizione è il bastione – assunto come “iato” nella continuità della murazione – che utilizza un varco di circa 30 metri presente nella cortina, definito dall’assenza di una delle parcelle proprietarie, in cui penetra una inedita presenza naturale
Famennian chondrichthyan microremains from Morocco and Sardinia
No full textNew material from the Famennian of Morocco in the southern Maider comprises chondrichthyan teeth (Thrinacodus, Cobelodus,
Denaea, Stethacanthus), actinopterygian remains (scales, teeth and hemilepidotrichium) and one acanthodian scale. The absence of crushing
teeth suggests deeper water environments for the Maider Basin than the Tafilalt Basin. Vertebrate microremains from the Famennian of Sardinia,
including Siamodus and Jalodus teeth, are illustrated and described. Ichthyofaunal relationships of the North Gondwanan platform during the
Famennian are examined
Permian–Triassic boundary enviromental and biotic changes: the Bulla parastratotype, Italy.
No full text- …
