86 research outputs found
Making a Big Splash with Louisiana Fishes
This book is a companion piece to Making a Big Splash with Louisiana Fishes, an exhibit created in 2012 at Louisiana State Universityâs Museum of Natural Science (MNS)https://digitalcommons.lsu.edu/spmns/1002/thumbnail.jp
Climat et niveau de lâocĂ©an Atlantique restituĂ©s en Espagne du Sud-Ouest de 6,3 Ă 5,2 Ma. Implications sur la Crise messinienne en MĂ©diterranĂ©e
The Mio-Pliocene succession of Andalusia on the Atlantic coast (Guadalquivir Basin) is known
as one of the former stratotype candidate for the Andalusian Stage, proposed during the seventies as the last
stage of the Miocene. Its type section is located in Carmona, east of Seville. Our investigation includes the
drilling of three cored boreholes, which provide bio- and magnetic-stratigraphic data in complement to preexisting industrial information, and a high-resolution palynological analysis (pollen grains, spores and
dinoflagellate cysts). The pollen flora and its climatic quantification provide the mean to correlate the section
to the oxygen isotope curve from the Montemayor-1 borehole, located about 80 km to theWest of Carmona.
The variations in the ratio between dinoflagellate cysts and pollen grains are used to identify high and low
oceanic levels, consistently with a recent paleobathymetric reconstruction based on foraminifera: the two
lowest levels being successively marked by the deposit of a littoral calcarenite (the Calizza Tosca
Formation) then by a subaerial erosive episode. Based on the correlation with the Montemayor-1 regional
drilling, the two major lowerings in oceanic level observed at Carmona are linked with the two episodes of
the Messinian Crisis. The interlocking position of the high-energy sandstone deposits inscribed in the
Messinian valley leads to an assessment of a drop in the global oceanic level of about 114m at the beginning
of the paroxysm of the Messinian Crisis, amplitude to be moderated with respect to the potential effect of
isostatic readjustements due to the Messinian Crisis. Comparisons are discussed with the amplitude of the
Messinian Erosional Surface in theWest-Alboran Basin which potentially remained suspended and fed with
Atlantic waters during the height of the crisis and isolated from the rest of the almost totally dried
Mediterranean Basin. The quantified climate constructed from the pollen records confirms that dry
conditions existed before the Messinian Crisis in Southern Mediterranean latitudes including the Atlantic
side, making the Mediterranean Sea climatically predisposed to desiccation. Atlantic sea-level variations
observed in the Guadalquivir region and measured at Carmona suggest that global glacio-eustatism
somewhat facilitated the onset and completion of the Messinian Crisis in the Mediterranean Basin. At last,
this work allows to discriminate two regional erosive events: the first one, dated at 5.60 Ma, of fluvial origin
in relation with global eustasy; the second one, submarine, occurred just before 5.33 Ma, and referred to the
strain exerted by the Guadalquivir olistostrome.La succession mio-pliocĂšne dâAndalousie atlantique (bassin du Guadalquivir) est connue comme ancienne candidate pour le stratotype de lâAndalousien, proposĂ© comme dernier Ă©tage du MiocĂšne dans les annĂ©es 70. Sa coupe-type est situĂ©e Ă Carmona, Ă lâest de SĂ©ville. Nos travaux comprennent notamment la rĂ©alisation de trois forages carottĂ©s oĂč furent acquises des donnĂ©es bio- et magnĂ©to-stratigraphiques complĂ©mentaires aux informations connues
des recherches industrielles et, surtout, une analyse palynologique (grains de pollen et kystes de
dinoflagellés) à haute résolution. La flore pollinique et la quantification climatique autorisent des
corrélations climatostratigraphiques avec la courbe d18O du forage Montemayor-1 implanté prÚs de Huelva.
Les variations du rapport entre kystes de dinoflagellĂ©s et grains de pollen permettent dâidentifier les hauts et
bas niveaux océaniques en accord avec une récente estimation paléobathymétrique basée sur les
foraminifĂšres, les deux plus bas niveaux Ă©tant successivement marquĂ©s par le dĂ©pĂŽt dâune calcarĂ©nite
littorale (Formation de la Caliza Tosca) puis par un épisode érosif subaérien. AprÚs corrélation avec le forage
Montemayor-1, ces deux baisses du niveau océanique sont respectivement mises en correspondance avec les
deux temps de la Crise messinienne. LâemboĂźtement des dĂ©pĂŽts grĂ©seux Ă haute Ă©nergie inscrits dans la
vallĂ©e messinienne conduit Ă Ă©valuer une chute du niveau atlantique dâenviron 114m lors du paroxysme de
la Crise messinienne, amplitude à modérer toutefois compte tenu du possible effet des rebonds isostatiques
liĂ©s Ă la Crise messinienne. Des comparaisons sont discutĂ©es avec lâampleur de lâĂ©rosion messinienne dans
le bassin ouest-Alboran potentiellement resté suspendu et alimenté en eaux atlantiques pendant le
paroxysme de la crise et isolé du reste du bassin méditerranéen quasi-totalement asséché. Les restitutions
quantifiées du climat comparées entre la province atlantique et le domaine méditerranéen confirment les
conditions xériques des latitudes sud-méditerranéennes s.l. et ainsi la prédisposition climatique de la
Méditerranée à la dessiccation. Les variations du niveau atlantique observées dans la région du Guadalquivir
et mesurées à Carmona suggÚrent que le glacio-eustatisme global a quelque peu contribué au déclenchement
et Ă lâachĂšvement de la Crise messinienne en MĂ©diterranĂ©e. Ce travail permet enfin de discriminer deux
Ă©vĂ©nements Ă©rosifs rĂ©gionaux : le premier Ă 5,60 Ma, dâorigine fluviatile en relation avec lâeustatisme
global, le second intervenu peu avant 5,33 Ma, sous-marin, liĂ© aux contraintes exercĂ©es par lâolistostrome du
Guadalquivir.CNRS-INSU, Total and Elf-Aquitaine companie
Fungi in a Warmer World: Middle Miocene Fungal Assemblages and Diversity from Alum Bluff, Florida
Fungi play a key role in the terrestrial carbon cycle, soil formation, and overall plant growth as terrestrial decomposers (1, 2). Thus, the study of fungi, especially in the fossil record, is critical to understanding how fungal assemblages will react to future warming events. Fossil fungi provide a large-scale, long-term dataset unavailable from modern records, allowing for the generation of viable paleoclimate reconstructions and predictions (3, 4). Despite their importance and advantages in forming ecological and climatological interpretations, deep-time fungi have been underutilized (3). The Fungi in a Warmer World (FiaWW) project aims to deliver the first global view of fungal biodiversity, ecology, and biogeography for the Miocene Climate Optimum (MCO): the warmest interval of the last 23 MY. The MCO is a good proxy for near-future climate change scenarios because atmospheric CO2 concentrations ranged between current concentrations of ~400ppm and future projected concentrations for the end of this century (5, 6).https://scholarworks.moreheadstate.edu/celebration_posters_2022/1040/thumbnail.jp
New insights on the Sorbas Basin (SE Spain): the onshore reference of the Messinian Salinity Crisis
International audienceThe Sorbas Basin is the land reference of the Messinian Salinity Crisis (MSC) that affected the Mediterranean Sea in the latest Miocene. Its stratigraphy has been re-visited using calcareous nannofossils and planktonic foraminifers, which provide a reliable biostratigraphic frame and lead to particularly specify the relationships between the Sorbas and Zorreras members with Yesares evaporites.The evaporites overlie a shallowing upward sequence ending with the deposition of the Reef Unit and Terminal Carbonate Complex (TCC) on the periphery of the basin. The reefal carbonates of the TCC are overlain by clastic deposits that are foreset beds of post-MSC Gilbert-type fan deltas developed on the northern edge of the basin. These sedimentary structures are separated from reefal carbonates and the Reef Unit by the Messinian Erosional Surface (MES). The various facies of the Sorbas Member have been correlated with the bottomset beds of the Gilbert-type fan deltas despite some differences in palaeobathymetry. In the southeastern periphery of the basin, the MES separates the Sorbas Member from the Yesares gypsums. In the central part of the basin, a hiatus characterizes the contact between these members. The Zorreras Member postdates the MSC and entirely belongs to Zanclean. Its white âLago Mareâ layers are lagoonal deposits, the fauna of which is confirmed to result from MediterraneanâParatethys high sea-level exchange after the post-MSC marine reflooding of the Mediterranean Basin.This study allows to re-assert the two-step scenario of the MSC (Clauzon et al., 1996) with the following events:- at 5.971â5.600 Ma, minor sea-level fall resulting in the desiccation of this peripheral basin with secondary fluctuations;- at 5.600â5.460 Ma, significant subaerial erosion (or lack of sedimentation) caused by the almost complete desiccation of the Mediterranean Sea;- instantaneous marine reflooding, accepted at 5.460 Ma, followed by continuing sea-level rise
New Insights on the Sorbas Basin (SE Spain): the onshore reference of the Messinian Salinity Crisis
The Sorbas Basin is the land reference of the Messinian Salinity Crisis (MSC) that affected the Mediterranean Sea in the latest Miocene. Its stratigraphy has been re-visited using calcareous nannofossils and planktonic foraminifers, which provide a reliable biostratigraphic frame and lead to particularly specify the relationships between the Sorbas and Zorreras members with Yesares evaporites. The evaporites overlie a shallowing upward sequence ending with the deposition of the Reef Unit and Terminal Carbonate Complex (TCC) on the periphery of the basin. The reefal carbonates of the TCC are overlain by clastic deposits that are foreset beds of post-MSC Gilbert-type fan deltas developed on the northern edge of the basin. These sedimentary structures are separated from reefal carbonates and the Reef Unit by the Messinian Erosional Surface (MES). The various facies of the Sorbas Member have been correlated with the bottomset beds of the Gilbert-type fan deltas despite some differences in palaeobathymetry. In the southeastern periphery of the basin, the MES separates the Sorbas Member from the Yesares gypsums. In the central part of the basin, a hiatus characterizes the contact between these members. The Zorreras Member postdates the MSC and entirely belongs to Zanclean. Its white "Lago Mare" layers are lagoonal deposits, the fauna of which is confirmed to result from Mediterranean-Paratethys high sea-level exchange after the post-MSC marine reflooding of the Mediterranean Basin. This study allows to re-assert the two-step scenario of the MSC (Clauzon et al., 1996) with the following events: - at 5.971-5.600 Ma, minor sea-level fall resulting in the desiccation of this peripheral basin with secondary fluctuations; - at 5.600-5.460 Ma, significant subaerial erosion (or lack of sedimentation) caused by the almost complete desiccation of the Mediterranean Sea; - instantaneous marine reflooding, accepted at 5.460 Ma, followed by continuing sea-level rise
Constraints on the Timing and Extent of Deglacial Grounding Line Retreat in West Antarctica
Projections of Antarctica\u27s contribution to future sea level rise are associated with significant uncertainty, in part because the observational record is too short to capture long-term processes necessary to estimate ice mass changes over societally relevant timescales. Records of grounding line retreat from the geologic past offer an opportunity to extend our observations of these processes beyond the modern record and to gain a more comprehensive understanding of ice-sheet change. Here, we present constraints on the timing and inland extent of deglacial grounding line retreat in the southern Ross Sea, Antarctica, obtained via direct sampling of a subglacial lake located 150 km inland from the modern grounding line and beneath \u3e1 km of ice. Isotopic measurements of water and sediment from the lake enabled us to evaluate how the subglacial microbial community accessed radiocarbon-bearing organic carbon for energy, as well as where it transferred carbon metabolically. Using radiocarbon as a natural tracer, we found that sedimentary organic carbon was microbially translocated to dissolved carbon pools in the subglacial hydrologic system during the 4.5-year period of water accumulation prior to our sampling. This finding indicates that the grounding line along the Siple Coast of West Antarctica retreated more than 250 km inland during the mid-Holocene (6.3 ± 1.0 ka), prior to re-advancing to its modern position
First Record of Fungal Diversity in the Tropical and Warm-Temperate Middle Miocene Climate Optimum Forests of Eurasia
The middle Miocene Climate Optimum (MMCO) was the warmest interval of the last 23 million years and is one of the best analogs for proposed future climate change scenarios. Fungi play a key role in the terrestrial carbon cycle as dominant decomposers of plant debris, and through their interactions with plants and other organisms as symbionts, parasites, and endobionts. Thus, their study in the fossil record, especially during the MMCO, is essential to better understand biodiversity changes and terrestrial carbon cycle dynamics in past analogous environments, as well as to model future ecological and climatic scenarios. The fossil record also offers a unique long-term, large-scale dataset to evaluate fungal assemblage dynamics across long temporal and spatial scales, providing a better understanding of how ecological factors influenced assemblage development through time. In this study, we assessed the fungal diversity and community composition recorded in two geological sections from the middle Miocene from the coal mines of Thailand and Slovakia. We used presence-absence data to quantify the fungal diversity of each locality. Spores and other fungal remains were identified to modern taxa whenever possible; laboratory codes and fossil names were used when this correlation was not possible. This study represents the first of its kind for Thailand, and it expands existing work from Slovakia. Our results indicate a total of 281 morphotaxa. This work will allow us to use modern ecological data to make inferences about ecosystem characteristics and community dynamics for the studied regions. It opens new horizons for the study of past fungal diversity based on modern fungal ecological analyses. It also sheds light on how global variations in fungal species richness and community composition were affected by different climatic conditions and under rapid increases of temperature in the past to make inferences for the near climatic future
The dinoflagellate cyst genera Achomosphaera Evitt 1963 and Spiniferites Mantell 1850 in Pliocene to modern sediments: a summary of round table discussions
Source at https://doi.org/10.1080/01916122.2018.1465739. We present a summary of two round-table discussions held during two subsequent workshops in Montreal (Canada) on 16 April 2014 and Ostend (Belgium) on 8 July 2015. Five species of the genus Achomosphaera Evitt 1963 and 33 of the genus Spiniferites Mantell 1850 emend. Sarjeant 1970 occuring in Pliocene to modern sediments are listed and briefly described along with remarks made by workshop participants. In addition, several holotypes and topotypes are reillustrated. Three species previously assigned to Spiniferites are here considered/accepted as belonging to other genera: Impagidinium inaequalis (Wall and Dale in Wall et al.1973) Londeix et al. 2009, Spiniferites? rubinus (Rossignol 1962 ex Rossignol 1964) Sarjeant 1970, and Thalassiphora balcanica Baltes ̧ 1971. This summary forms the basis for a set of papers that follows, where points raised during the workshops are explored in greater detail
Life and death in the Chicxulub impact crater: a record of the PaleoceneâEocene Thermal Maximum
latitudes, with sea surface temperatures at some localities exceeding the 35ââC at which marine organisms experience heat stress. Relatively few equivalent terrestrial sections have been identified, and the response of land plants to this extreme heat is still poorly understood. Here, we present a new record of the PETM from the peak ring of the Chicxulub impact crater that has been identified based on nannofossil biostratigraphy, an acme of the dinoflagellate genus Apectodinium, and a negative carbon isotope excursion. Geochemical and microfossil proxies show that the PETM is marked by elevated TEXH86-based sea surface temperatures (SSTs) averaging âŒ37.8ââC, an increase in terrestrial input and surface productivity, salinity stratification, and bottom water anoxia, with biomarkers for green and purple sulfur bacteria indicative of photic zone euxinia in the early part of the event. Pollen and plants spores in this core provide the first PETM floral assemblage described from Mexico, Central America, and the northern Caribbean. The source area was a diverse coastal shrubby tropical forest with a remarkably high abundance of fungal spores, indicating humid conditions. Thus, while seafloor anoxia devastated the benthic marine biota and dinoflagellate assemblages were heat-stressed, the terrestrial plant ecosystem thrived
Seismic stratigraphic analysis of late Wisconsinan shelf-margin depocenters offshore Mississippi, Alabama and west Florida, establishes synchroneity of depositional episodes at the three sites
ThĂšse de doctorat annexe -- UCL, 199
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