Papers by Nicolas Goudemand
Palaeogeography Palaeoclimatology Palaeoecology 308, 2011
Lower to Middle Triassic ostracods from the Tulong section, south Tibet, are described here for t... more Lower to Middle Triassic ostracods from the Tulong section, south Tibet, are described here for the first time. Samples from the first two stages of the Early Triassic (Griesbachian and Dienerian) are barren of ostracods; the following stage (Smithian) revealed low diversity ostracod faunas; a substantial diversification in taxa began at the base of the fourth stage (Spathian) and developed into the first stage of the Middle Triassic (Anisian). Furthermore, exploration of additional feeding modes is developed in the Spathian and Anisian, with notable occurrence of filter-feeding taxa. High abundance of filter-feeding ostracods in Spathian and lower Anisian units indicates that benthic habitats became oligotrophic. These habitats typically harbored ostracod faunas of Mesozoic affinities, suggesting that the evolutionary turnover of ostracods was fostered by the declining input of nutrients from the Spathian on. Marked faunal similarities with other Tethyan areas, mainly the northern part of Tethys, are observed during Spathian and Anisian times.► In this study we examine ostracod (Crustacea) faunas from Early and early Middle Triassic of Tulong section, Tibet. ► We examine palaeoenvironmental significance of these assemblages. ► We consider biodiversity indices in relation to feeding modes of ostracods. ► We give new insights into recovery mode in the aftermath of the end-Permian extinction.
Geology, 2006
Four volcanic-ash beds bracket the Early-Middle Triassic boundary, as defined by conodont biostra... more Four volcanic-ash beds bracket the Early-Middle Triassic boundary, as defined by conodont biostratigraphy, in a stratigraphic section in south China. High-precision U-Pb dates of single zircons allow us to place the Early to Middle Triassic (Olenekian-Anisian) boundary at 247.2 Ma. Magnetic-reversal stratigraphy allows global correlation. The new dates constrain the Early Triassic interval characterized by delayed biotic recovery and carbon-cycle instability to ϳ5 m.y. This time constraint must be considered in any model for the end-Permian extinction and subsequent recovery.
Changes of community structure in response to competition usually take place on timescales that a... more Changes of community structure in response to competition usually take place on timescales that are much too short to be visible in the geological record. Here we report the notable exception of a benthic marine community in the wake of the end-Permian mass extinction, which is associated with the microbial limestone facies of the earliest Triassic of South China. The newly reported fauna is well preserved and extraordinarily rich (30 benthic macroinvertebrate species, including the new species Astartella? stefaniae (Bivalvia) and Eucochlis obliquecostata (Gastropoda)) and stems from an environmentally stable setting providing favourable conditions for benthic organisms. Whereas changes in the taxonomic composition are negligible over the observed time interval of 10–100 ka, three ecological stages are identified, in which relative abundances of initially rare species continuously increased at the cost of previously dominant species. Concomitant with the changes of dominant species is an increase in faunal evenness and heterogeneity. In the absence of both environmental and taxonomic changes, we attribute this pattern to the long-term effects of interspecific competition, which acted at an unusually slow pace because the number of competing species and potential immigrants was dramatically reduced by the end-Permian mass extinction. We suggest that these non-actualistic conditions led to decreased rates of niche differentiation and hence to the delayed rediversification of benthos that characterizes the aftermath of the greatest Phanerozoic mass extinction event. A hyperbolic diversification model is proposed, which accounts for the positive relationship between the intensity of interspecific competition and the rate of niche differentiation and resolves the conundrum of delayed rediversification at a time when niche space was largely vacated.
Sedimentary Geology, 2009
The Lower Triassic sedimentary and carbonate/organic carbon isotope records from the Tulong area ... more The Lower Triassic sedimentary and carbonate/organic carbon isotope records from the Tulong area (South Tibet) are documented in their integrality for the first time. New age control is provided by ammonoid and conodont biostratigraphy. The basal Triassic series consists of Griesbachian dolomitic limestones, similar to the Kathwai Member in the Salt Range (Pakistan) and to the Otoceras Beds in Spiti (India). The overlying thin-bedded limestones of Dienerian age strongly resemble the Lower Ceratite Limestone of the Salt Range. They are followed by a thick series of dark green, silty shales of Dienerian–early Smithian age without fauna that strikingly resemble the Ceratite Marls of the Salt Range. This interval is overlain by thin-bedded, light grey fossil-rich limestones of middle to late Smithian age, resembling the Upper Ceratite Limestone of the Salt Range. These are followed by a shale interval of early Spathian age that has no direct counterpart in other Tethyan sections. Carbonate production resumes during the late early and middle Spathian with the deposition of red, bioclastic nodular limestone (“Ammonitico Rosso” type facies). Apart from its colour this facies is similar to the one of the Niti Limestone in Spiti and of the Spathian nodular limestone in Guangxi (South China). As in other Tethyan localities such as Spiti, the early–middle Anisian part of the Tulong section is strongly condensed and is characterized by grey, thin-bedded limestones with phosphatized ammonoids.As for many other Tethyan localities the carbon isotope record from Tulong is characterized by a late Griesbachian–Dienerian positive δ13Ccarb excursion (2‰), and a very prominent positive excursion (5‰) at the Smithian–Spathian boundary, thus confirming the well-documented perturbations of the global carbon cycle following the Permian–Triassic mass extinction event.
New ichnological data from the Lower Triassic Werfen Formation (Dolomites, Italy) revealed an une... more New ichnological data from the Lower Triassic Werfen Formation (Dolomites, Italy) revealed an unexpectedly diverse and complex ichnofauna in mixed siliclastic–carbonate shelf sediments of the western tropical Tethys shortly after the end-Permian mass extinction event. Common elements are Thalassinoides, Palaeophycus and Planolites. Other associated ichnogenera include Spongeliomorpha, Rhizocorallium, Lockeia, Catenichnus, Helminthopsis, and Taenidium. One structure is tentatively determined as Curvolithus. Biostratigraphic data (conodonts and bivalves) of the trace fossil interval (lower Seis/Siusi Member) suggest a late Griesbachian age, less than 1 Ma after the end-Permian mass extinction event. Similarly diverse ichnofossil communities from this time interval have recently been described from the Boreal Realm, but this is the first record of a diverse Griesbachian ichnoassemblage from the tropics, indicating that the early recovery of trace fossil producers was not latitudinally restricted, as previously proposed. Accordingly, relatively advanced recovery stages were reached on a global scale much earlier than the Spathian as is commonly acknowledged. The early and interregional peak in ichnofaunal recovery implies subsequent ecological setbacks in post-Griesbachian times that explain the overall delay of benthic recovery until the Spathian. Rather than persistent catastrophic conditions during the Griesbachian, a global and synchronous succession of crises and relaxation phases after the Griesbachian is proposed as an explanatory model for the recovery pattern of benthic ecosystems.
A new sampling of Early Triassic (Griesbachian) conodonts is obtained from the microbialite overl... more A new sampling of Early Triassic (Griesbachian) conodonts is obtained from the microbialite overlying the latest Permian peri-reefal shallow water limestone in Wuzhuan section (Nanpanjiang Basin, Guangxi, South China). High resolution sam-pling in the lower twelve meters of the Luolou Formation provides rather diversified conodont faunas and allows const-ructing a well resolved conodont distribution for this crucial earliest Triassic interval. In the Wuzhuan section, the nine meters thick microbialite is bracketed by two calcarenite beds and contains several fossiliferous lenses. The co-occurrence of typical Permian foraminifera such as Paraglobivalvulina mira (Reitlinger) and Dagmarita chanakchiensis (Reitlinger) in the calcarenite underlying the microbialite indicates a late Permian age. Our preliminary results indicate the presence of one residual maximal horizon (RMH) based on conodont faunas in the microbialite and of a second one in the overlying calca-renite. The lowest RMH o...
Palaeontology, 2015
Changes of community structure in response to competition usually take place on timescales that a... more Changes of community structure in response to competition usually take place on timescales that are much too short to be visible in the geological record. Here we report the notable exception of a benthic marine community in the wake of the end-Permian mass extinction, which is associated with the microbial limestone facies of the earliest Triassic of South China. The newly reported fauna is well preserved and extraordinarily rich (30 benthic macroinvertebrate species, including the new species Astartella? stefaniae (Bivalvia) and Eucochlis obliquecostata (Gastropoda)) and stems from an environmentally stable setting providing favourable conditions for benthic organisms. Whereas changes in the taxonomic composition are negligible over the observed time interval of 10-100 ka, three ecological stages are identified, in which relative abundances of initially rare species continuously increased at the cost of previously dominant species. Concomitant with the changes of dominant species is an increase in faunal evenness and hetero-geneity. In the absence of both environmental and taxonomic changes, we attribute this pattern to the longterm effects of interspecific competition, which acted at an unusually slow pace because the number of competing species and potential immigrants was dramatically reduced by the end-Permian mass extinction. We suggest that these non-actualistic conditions led to decreased rates of niche differentiation and hence to the delayed rediversification of benthos that characterizes the aftermath of the greatest Phanerozoic mass extinction event. A hyperbolic diversification model is proposed, which accounts for the positive relationship between the intensity of interspecific competition and the rate of niche differentiation and resolves the conundrum of delayed rediversification at a time when niche space was largely vacated.
Journal of Experimental Zoology Part B-molecular and Developmental Evolution, 2010
This article explores the close relationships between growth rate and allometries of molluscan sh... more This article explores the close relationships between growth rate and allometries of molluscan shells. After reviewing the previous theoretical approaches devoted to the understanding of shell form and its morphogenesis, we present a free-form vector model which can simulate apertural shape changes and nonlinear allometries. Shell morphology is generated by iteratively adding a growth increment onto the last computed aperture. The first growth increment defines so-called growth vectors which are assumed to be constant in direction (relative to the last computed aperture position) during a simulation of a shell (ontogeny). These growth vectors are uniformly scaled at each time step according to various growth rate curves that are used to simulate the mantle growth over time. From the model, we derive morphometric variables that illustrate the ontogenetic trajectories in time–size–shape space. We investigate the effects of changing the growth curves types, growth rate parameters and growth vector maps on the direction, speed and patterns of ontogenetic allometries. Because this model focuses the issue on time, it highlights a plausible effect of growth rate on shell shape and illustrates some fundamental geometrical properties of the logarithmic spiral, in particular the close relationship between the size and the geometry of growth increments. This model could be used to develop a mathematically data-driven approach where experimentally obtained growth curves could be used as inputs in the model. More generally, our study recalls the role of growth rates in the generation of allometries. J. Exp. Zool. (Mol. Dev. Evol.) 314B:280–302, 2010. © 2010 Wiley-Liss, Inc.
Ber. Inst. Erdwiss. K.-F.-Univ. Graz, Bd. 21, p. 31, Jul 22, 2015
In the Batain region of Oman, basal Triassic crinoid limestones occur as exotic boulders within t... more In the Batain region of Oman, basal Triassic crinoid limestones occur as exotic boulders within the Jurassic Guweiza Formation near Asselah. Some of these boulders contain the conodont association Hindeodus parvus -Isarcicella isarcica, indicating a Griesbachian age. Disarticulated crinoid columnal segments are the main component of these calcarenitic boulders. Additional fauna include small-sized ammonoids (Permian holdovers such as medlicottids and xenodiscids), numerous gastropods, ostracods, bivalves, brachiopods, echinoid spines, microconchids, and foraminifers. The rock is a crinoidal packstone with a dominantly micritic matrix and a great abundance of bioclasts, showing in some cases an early phase of cementation (partly coarse spar and cement fringe). The cylindrical columnals are 0.2 -2mm in diameter and display up to 32 radial ridges. These ossicles are not well sorted and mixed with mostly unbroken molluscan shells showing no signs of abrasion or bioerosion. This preservation suggests minimal lateral transport. Thin-sections also reveal that the limestone yield a diverse assemblage of small gastropods which cannot be extracted from the rock due to strong cementation. The neritimorph gastropod Naticopsis sp. is abundant. Their specimens are well-preserved due to a thin, primarily calcitic outer shell layer. The size of these specimens of Naticopsis sp. can exceed 20 mm, demonstrating the presence of relatively large gastropods ('Gullivers') (1) as soon as during the Griesbachian, thus questioning the presumed Lilliput Effect that would have affected gastropods after the end-Permian crisis. Late Paleozoic Naticopsis species range from less than 10 mm to more than 130 mm in size. 20 mm as reported here for the present Griesbachian species from Oman is common in many Late Paleozoic Naticopsis species. Naticopsis, has been reported from various Early Triassic sites including the Wadi Wasit block of the Hawasina nappes in Oman Mountains (2) (3). However, Naticopsis occurrences from Asselah and Wadi Wasit are not conspecific. Despite the seemingly low taxonomic diversity of earliest Triassic crinoids (but see (4)), the Batain blocks show that some populations were sufficiently abundant to produce material in rock forming quantity. These neritic plateaus colonized by crinoids and various skeletal organisms obviously functioned as local and healthy carbonate factories. Such crinoidal sediments are rare during the Griesbachian: they have never been reported from the inter-tropical realm (Tethyan northern margins and South China) and are known only from mid-latitude localities such as Wadi Wasit (2) (4), Batain (this study) and Salt Range (dolomitized encrinite at the base and within the Kathwai Member) (5). Yet, it is not understood what factor(s) constrained their occurrences. According to (6), after the end-Triassic extinction, crinoidal limestones often developed on topographic highs and seamounts of the Western Tethys and corresponded to stratigraphically condensed sequences. As for the postextinction Early Jurassic, the Griesbachian crinoidal limestones developed on hard-substrate, welloxygenated submarine topographic highs, during the drowning and faulting of a former shallow platform. These carbonate 'oases' indeed imply: (a) paleotopographic areas protected from clastic input, (b) an adequate (shallow?) water depth, and (c) normal water chemistry (oxygen, pH, salinity) and temperature. They contradict the common view of global, homogeneously catastrophic conditions in the oceans in the direct aftermath of the end-Permian mass extinction.
Cretaceous Research, 2009
Following the end-Permian mass extinction, ammonoids were among the fastest clades to recover , w... more Following the end-Permian mass extinction, ammonoids were among the fastest clades to recover , with at least two diversification phases during the Early Triassic. Diversification first peaked during the Smithian and was followed by a marked extinction phase at the end of this (sub-)stage. It was then followed by a second and massive evolutionary radiation during the Spathian. The well-documented, ammonoid-rich Smithian succession of NW Guangxi, South China is subdivided into three main faunas, i.e., the "Flemingites rursiradiatus beds", the "Owenites koeneni beds" and the "Anasibirites multiformis beds," in ascending order (Brayard and Bucher, subm.). Ongoing work on other Smithian Tethyan sections such as Tulong (Tibet), Spiti (India), Salt Range (Pakistan), and Oman (exotic blocks at Baid, Wadi Musjah and Jabal Safra) shows that these subdivisions have Tethyan-wide correlatives. Moreover, even finer subdivisions can be correlated throughout the studied basins ( .
Swiss Journal of …
CITATIONS 18 READS 85 5 authors, including: Some of the authors of this publication are also work... more CITATIONS 18 READS 85 5 authors, including: Some of the authors of this publication are also working on these related projects: The second stage of recovery from the end-Permian mass extinction: Ecology, diversity partitioning, and rank-abundance distributions in Middle Triassic marine level-bottom communities View project PaleoDeep: Paleobiology of the deep-sea through time and space View project Andrzej Kaim Polish Academy of Sciences 75 PUBLICATIONS 952 CITATIONS SEE PROFILE Alexander Nützel Bayerische Staatssammlung für Paläontologi…
2008 Joint Meeting of …, Jan 1, 2008
Benthic organisms are known to have recovered much slower after the end-Permian mass extinction e... more Benthic organisms are known to have recovered much slower after the end-Permian mass extinction event than ammonoids, but hitherto the poor age-control of most Early Triassic benthic faunas prevented detailed comparisons. A new dataset that includes occurrences of bivalve and ...
Applied Optics, Jan 1, 2006
2008 Joint Meeting of …, Jan 1, 2008
Ongoing work in California, S-China, Tibet, Pakistan and Oman has led to a refined biochronologic... more Ongoing work in California, S-China, Tibet, Pakistan and Oman has led to a refined biochronologic subdivision of the late Early Triassic and allows reconstructing a high resolution diversity time series, partly constrained by new U-Pb ages from S-China [1-2].
CITATIONS 3 READS 88 6 authors, including:
Proceedings of the …, Jan 1, 2011
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Papers by Nicolas Goudemand