Sciency Thoughts: Palaeocene-Eocene Thermal Maximum

Showing posts with label Palaeocene-Eocene Thermal Maximum. Show all posts

Friday, 14 April 2023

Examining the impact of the Palaeocene–Eocene Thermal Maximum on sedimentation in the Gulf of Mexico.

Roughly 56 million years ago, global temperatures abruptly rose by 5-9°, leading to profound environmental changes across the planet, an event known as the Palaeocene–Eocene Thermal Maximum. This event was marked (and probably caused by) a sharp rise in atmospheric carbon dioxide, something marked in the rock record by a 3.0‰ negative carbon isotope excursion (three parts per thousand drop in the proportion of carbon¹³ to total carbon), which developed over a period of less than 5000 years. Three main stages to this negative carbon isotope extension have been detected; the onset, during which the proportion of carbon¹³ dropped from the pre-excursion level to the excursion level; the body, during which the proportion of carbon¹³ remained steady at the new, lower level; and the recovery, during which the proportion of carbon¹³ returned to the pre-excursion level.

This interval was also marked by a dramatic increase in the prevalence of the Dinoflagellate cyst Apectodinium spp., and a widespread dissolution of carbonates (a sign that the sea had become slightly acidic due to the higher atmospheric carbon dioxide levels). The negative carbon isotope excursion has been detected in a wide range of sedimentary setting, from continental interiors to ocean basins, although its cause is still debated. It is generally accepted that the rise in atmospheric carbon dioxide, combined with the drop in the proportion of carbon¹³, is indicative of the atmosphere receiving a sudden, and very large, input of carbon¹³-depleted carbon dioxide, with the most popular explanations for this being a volcanic source or a sudden increase in the proportion of carbon dioxide being released from land Plants and soils (this could be response to heating, leading to a feed-back loop in which the released carbon dioxide causes a rise in temperature, leading to further carbon dioxide being released, something which concerns climate scientists studying current rising global temperatures). It has also been suggested that the initial pulse of heating might have been caused by an increase in the proportion of biogenic methane (another potent greenhouse gas).

The Gulf of Mexico forms an enclosed basin within the area bounded by the southern coast of the United States, the east coasts of northern Mexico, and the Yucatan and Florida Peninsula. This basin formed by sea-flood spreading during the Jurassic and Early Cretaceous, with deposits of clasitic and carbonate sediments building up along its northern margin during the Cretaceous and Palaeocene. This sedimentation increased rapidly during the Palaeocene–Eocene Thermal Maximum, leading to a prograding (movement of shoreline towards the sea) of the fluvio-deltaic Wilcox Group. During this time, most of what is now the southern United States formed a single catchment area, driven by the Laramide Orogeny as the Rocky Mountains began to form. The sedimentary material formed by erosion within this catchment was carried into the Gulf of Mexico, forming the deltas of the Houston, Mississippi, and Rio Grande rivers. These sediments served as a trap for hydrocarbons derived from organic material swept into these deltas, which has led to extensive hydrocarbon exploration of the basin in the twentieth and twenty first centuries. This data has enabled geologists to build up a good picture of sedimentation rates within the Gulf of Mexico throughout the Cainozoic, with a distinct increase on sedimentation rates visible at the Palaeocene–Eocene Thermal Maximum.

The Wilcox Group is a succession of fluvial, deltaic, and shallow marine sediments, which outcrops in parts of Alabama and Texas, where it is targeted by numerous onshore oil wells. The group progresses offshore, where its outer margins contain turbidite deposits, which are drilled by offshore oil rigs. The Wilcox Group can be divided into Lower, Middle, and Upper units, which the base of the Upper Unit marked by the Yoakum Shale, which is thought to mark the onset of the Palaeocene-Eocene boundary. The carbon isotope excursion associated with the Palaeocene–Eocene Thermal Maximum has been detected at several locations within the Wilcox Group, although principally within the onshore fluvial and deltaic deposits and the plains of the Gulf of Mexico. Within the distal part of the submarine fan, the Palaeocene–Eocene Thermal Maximum has been detected biostratigraphically, but not through the detection of the carbon isotope excursion. There is localized evidence of environmental change within the delta, recorded by prograding of sediments over an area of thousands of kilometers, with material from river drainages reaching to the deep ocean floor.

The ability to connect a prograding deep sea fan to a well understood river catchment system provides a unique opportunity to study enviromental changes across an entire sedimentary system from the source to the outer part of the marine basin.

In a paper published in the journal Geology on 9 February 2023, Lucas Vimpere of the Department of Earth Sciences at the University of Geneva, Jorge Spangenberg of the Institute of Earth Surface Dynamics at the University of Lausanne, Marta Roige of the Departament de Geologia at the Universitat Autònoma de Barcelona, Thierry Adatte of the Institute of Earth Sciences at the University of Lausanne, Eric De Kaenel of DeKaenel Paleo-Research, Andrea Fildani of the Deep Time Institute, Julian Clark and Swapan Sahoo of Equinor, Andrew Bowman of the Louisiana Geological Survey, Pietro Sternai of the Dipartimento di Scienze dell’Ambiente e della Terra at the Università degli Studi di Milano-Bicocca, and Sébastien Castelltort, also of the Department of Earth Sciences at the University of Geneva, present the results of a study that located the isotopic signal of the Palaeocene–Eocene Thermal Maximum within marine sediments in the northern part of the Gulf of Mexico, use this data to place a chronostratigraphic data-point within the strata, and examine the relationship between sedimentation rates and climate change as recorded within the sediments of the Gulf of Mexico.

Vimpere et al. obtained a 543 m thick section from the Logan-1 ultra-deep-water wildcat well, which was sunk in 2011 on Walker Ridge Block, which includes the outer part of the Wilcox Group, about 400 km to the southeast of New Orleans. This well excavated a core beneath 2364 m of water, to a depth of 8351 m beneath sea level. One hundred and seventy eight samples were taken from this section, at three meter intervals, then subjected to bulk and clay X-ray diffraction, Rock-Eval pyrolysis, granulometric, organic carbon isotope, palynological, and calcareous nannofossil analyses.

Topobathymetric elevation model of North America showing the Logan-1 well location (drilled in 2011 on Walker Ridge Block 969, ID WR 969 ST0 #1) and present main geographic features. Depositional context during the Paleocene-Eocene transition is represented by Wilcox Group thickness and key tectono-stratigraphic events in the Gulf of Mexico sediment routing system. PETM; Palaeocene–Eocene Thermal Maximum. Vimpere et al. (2023).

Examination of palynomorphs and calcareous nanofossils identified the Palaeocene–Eocene Thermal Maximum interval as being present between 8181 and 8001 m within the Logan-1 core, and the Palaeocene-Eocene boundary as lying between the NP9 and NP10-0 horizons of the calcareous nannofossil assemblage. The carbon-isotope excursion can also be identified within the core, at 8196–8001 m, with an onset 15 m below the Palaeocene-Eocene boundary, and no hiatus in sediment deposition. This pattern has been observed at a variety of locations, and suggests a link between the onset of the Palaeocene–Eocene Thermal Maximum and late Palaeocene volcanism on the e North Atlantic volcanic province, the Caribbean, and mid-ocean ridge areas. The main body interval of the carbon-isotope excursion is found between 8196 and 8108 m, and the recovery phase between 8108 and 8101 m. This gives a Palaeocene–Eocene Thermal Maximum deposit with a thickness of 195 m, making it the thickest Palaeocene–Eocene Thermal Maximum deposit yet discovered. This contrasts with other well cores sunk in the Gulf of Mexico, in which the Palaeocene–Eocene Thermal Maximum sequence has been truncated. A marked increase in the abundance of Dinoflagellate cyst Apectodinium spp. was observed at 8169 m, while glauconite concentrations increased at 8172 m. Both of these are thought to represent sediments having become condensed, and a shift in the shoreline to landward, caused by deepening sealevels associated with the global temperature rise.

Carbon isotope, glauconite concentration, chronostratigraphic, and lithostratigraphic data and correlations with Gulf of Mexico standard stratigraphy for the section studied in the Logan-1 well (drilled in 2011 on Walker Ridge Block 969, ID WR 969 ST0 #1). δ13Corg measurements and three-point averages are illustrated by the circles and the curve, respectively. GR, gamma ray; Sh, shale; Slt, silt; Snd, sand; YS, Yoakum Shale; CIE, carbon isotope excursion; PETM, Palaeocene–Eocene Thermal Maximum. Nannofossils: Bomolithus aquilus, Discoaster araneus, Discoaster mahmoudii, Discoaster diastypus, Fasciculithus tympaniformis, Rhomboaster cuspis, Rhomboaster bitrifida, Tribrachiatus bramlettei, Discoaster mahmoudii, Coccolithus bownii, Bomolithus supremus, Tribrachiatus bramlettei, Thomsonipollis, Fasciculithus richardii, Caycedoae megastypus, Discoaster multiradiatus, Fasciculithus lillianiae, Fasciculithus richardii, Discoaster acutus. Vimpere et al. (2023).

These results suggest that, in this part of the Gulf of Mexico, sedimentation rates were significantly increased during the Palaeocene–Eocene Thermal Maximum. If the Palaeocene–Eocene Thermal Maximum is assumed to have lasted 170 000 years, then this part of the Gulf of Mexico apparently had an average sedimentation rate of 1.15 m per 1000 years during this interval. The main body of the event comprises 88 m of sediment, thought to have been laid down in 80 000 years, giving a sedimentation rate of 1.1 m per 1000 years, while the recovery period is represented by 107 m of sediment laid down in 118 000 years, giving a sedimentation rate of 1.18 m per 1000 years, although distinguishing the main body from the recovery period is difficult, leading to a substantial margin of error in these calculations.

The Yoakum Shale is considered to represent a maximum flooding surface, created when the Palaeocene–Eocene Thermal Maximum caused the shoreline to retreat by 150 m. In the submarine deposits of the Gulf Coastal Plain this corresponds with a drop in the amount of terrestrial sedimentary material arriving, and the formation of an number of submarine canyons, most notably the Yoakum Canyon off the coast of Texas. These canyons tended to funnel sediments down into the ocean basin, bypassing much of the continental shelf, which became starved of sediment. The sediments of the shelf show a higher proportion of marine palynomorphs (which settle out of the water column) than terrestrial palynomorphs (which are carried out to sea with sediment) during this interval, and are also enriched in glauconite (which only forms in marine settings) relative to the rest of the sediment column.

Palaeographic map of the northern Gulf of Mexico showing evolution of the depositional systems throughout the Paleocene–Eocene Thermal Maximum. Vimpere et al. (2023).

It could be presumed that the heating and increase in sealevel associated with the Palaeocene–Eocene Thermal Maximum led to the transgression onto the shores of the Gulf of Mexicoby itself, however Vimpere et al.'s findings suggest that this was at least in part due to subsidance of the coastal margins associated with the formation of the submarine canyons, although there is not sufficient data to make an absolute assessment of the influence of the two phenomena.

During the Early Eocene, uplift associated with the second pulse of the Laramide Orgeny forced the waterways carrying sediments into the Gulf of Mexico to shift towards the southwest. This is recorded in the Upper Wilcox deposits, where several major fluvio-deltaic systems are rejuvinated. This in turn led to stabilization of the system, with less wandering by channels, enabling sediments to build up and prograde out over the shelf margin. This prograding of the delta sediments is matched by the development of a sandy apron in the deep sea basin, probably formed as the prograding sediments reached the head of the submarine canyons.

Schematic representation of the evolution of the sediment-routing system of North America throughout the Palaeocene–Eocene Thermal Maximum. Increased channel mobility and floodplain reworking led to preferential transport of clays into the basin (i.e., Yoakum Shale) through bypass of the shelf within submarine canyons. Upper Wilcox corresponds to resuming of preferential transport of coarse material into basin-floor aprons due to progradation of deltaic sands onto the shelf and the mud removal by waves. Vimpere et al. (2023).

Within the Logan-1 drill core the Yoakum Shale is overlain by a series of sandy beds which reach from the top of the Yoakum at 8120 m up to 8007 m. This is thought to be linked to the development of a more extreme climate, which switched periodically between intense drought phases and intervals of heavy precipitation. This created periodic heavy flows within the river basins, washing out to see accumulated sands, derived from rocks uplifted by the Laramide Orogeny. The inshore environment is also likely to have suffered an increase in storm and wave action, washing sediments from the delta lobes down into the deep ocean basin.

Vimpere et al. were able to use a multi-disciplinary approach to locate the Palaeocene-Eocene boundary, Palaeocene–Eocene Thermal Maximum, and the associated carbon isotope excursion, in sediments about 400 km away from the nearest coast. The carbon isotope excursion here is 195 m thick, and confirmed to represent the Palaeocene–Eocene Thermal Maximum by palynological and microfossil analysis, making it the longest Palaeocene–Eocene Thermal Maximum section known. This implies that sedimentation rates in this part of the basin were extremely high during this interval, which in turn implies a strong sedimentological response to the changing hydrological conditions associated with the Palaeocene–Eocene Thermal Maximum. Since other fan deposits of equivalent age are known at many locations around the world, it is reasonable to assume that this was a global, rather than a regional, response to the Palaeocene–Eocene Thermal Maximum.

Monday, 29 September 2014

Calculating the temperature of tropical waters during the Palaeocene-Eocene Thermal Maximum.

The Palaeocene Era was a period of significant global warming, culminating in the Palaeocene-Eocene Thermal Maximum, when around 2000 gigatons of isotopicly light carbon are thought to have been released into the atmosphere over a relatively short time interval (less than 60 000 years), due to melting of deep-sea methane hydrates and permafrost in high latitude and altitude soils. This resulted in a brief period of extreme global warming driven by the sudden input of more-or-less all available greenhouse gasses into the atmosphere, then followed by a period of cooling in the early Eocene as these gasses were lost from the atmosphere.

It should be noted that predictions of the results of human-induced global warming in the near future often predict more severe warming than occurred at the end of the Palaeocene; this is because these scenarios include not just the melting of permafrost and methane hydrates due to warming, but also the pumping of large amounts of carbon dioxide from the burning of fossil fuels (which did not occur during the Palaeocene), and therefore resulting in a much more severe warming, albeit from a cooler starting point.

Though we know that the temperature rose sharply around the globe at the end of Palaeocene, exactly how far it rose in many areas is unclear. One such area is the tropical oceans, which are important for the understanding of global climate patterns. The best way of determining sea temperatures in the past is generally accepted to be oxygen isotope analysis of minerals from the preserved shells of pelagic or planktonic organisms. Such organisms, if they lived close to the surface in open water can give a good measure of the temperature of the water as warmer water contains a higher proportion of isotopicly heavy oxygen. Inshore waters are prone to more extreme temperature fluctuations, as water trapped in enclosed bays can be heated more extremely, but this does not reflect the temperature over wider areas and is therefore not considered useful for understanding global climate patterns.

However this is difficult to study for tropical waters around the Palaeocene-Eocene Thermal Maximum, as the rise in atmospheric carbon dioxide led to oceanic acidification (carbon dioxide dissolves in water to form carbonic acid), leading to a rise in the carbonate compensation depth (the depth beneath which calcium carbonate will dissolve in water – calcium carbonate dissolves more readily at greater pressure, resulting in a pressure boundary rises as the ocean becomes more acidic and falls as the acidity does). Thus many end-Palaeocene deep water sediments, from which microfossil shells are usually extracted to perform oxygen isotope analysis, lack any such shells.

In a paper published in the journal Geology on 25 July 2014, a team of scientists led by Tracy Aze of the School of Earth and Ocean Sciences at CardiffUniversity describe the results of a study of planktonic Foraminifera shells from a location in Tanzania interpreted as having been an outer shelf environment 19˚ from the equator, that was remote from any land but had a depth of only about 300 m (i.e. above the carbonate compensation depth).

Azeet al. analysed specimens of the Foraminifera Acarinina, Morozovella, and Subbotina from across the late Palaeocene and early Eocene. This resulted in a maximum temperature estimate close to the Thermal Maximum of ~36-43˚C, however the sediments around the Thermal Maximum are extremely depleted in Foraminifera, suggesting that temperatures may have been even higher, resulting either in seawater too acidic to preserve calcium carbonate shells or too warm to have been inhabited by Foraminifera.

A Foraminifera of the genus Morozovella. Clay Kelly et al. (2001).

Studies in other areas have suggested that Foraminifera from equatorial and tropical regions migrated towards the poles around the Thermal Maximum, while experiments on modern members of the group suggest that these are unable to tolerate temperatures much above ~33˚C, so that even if Palaeocene Foraminifera were more tolerant of high temperatures, it is difficult to see them surviving in water much above ~43˚C.

Thursday, 8 May 2014

Eocene non-marine Vertebrate remains from Banks Island in the western Canadian High Arctic.

The remains of a variety of non-marine Vertebrates have been recovered from Ellesmere and Axel Heiberg Islands in the eastern Canadian High Arctic from the 1970s onwards. These vertebrate assemblages date from early – middle Eocene (53–50 million years ago), when the islands were close to their current positions within the Arctic Circle, yet indicate that the area had a warm climate at the time. This has provided a useful window into climates in the Arctic close to the Eocene Thermal Maximum (roughly 53 million years ago).

In a paper published in the journal PLoS One on 1 May 2014, Jaelyn Eberle of the University of Colorado Museum of Natural History and the Department of Geological Sciences at the University of Colorado at Boulder, Michael Gottfried of the Department of Geological Sciences and Museum at Michigan State University, Howard Hutchison of the University of California Museum of Paleontology and Christopher Brochu of the Department of Earth and Environmental Sciences at the University of Iowa, describe a series of non-marine Vertebrate fossils from the Margaret Formation of the Eureka Sound Group on northern Banks Island in the western Canadian High Arctic.

The first fossil described is a lateral line scale from a Gar of the genus Atractosteus, which are currently found in the Southern United States, Mexico, Central America and parts of the Caribbean. This is 19 x 9 mm, with the distinctive elongate diamond shape of a Gar scale.

Lateral line scale of Atractosteus sp. from the Eocene of Banks Island, in medial (A) and lateral (B) views. Eberle et al. (2014).

The second fossil is a partial vertebra identified as having come from a Fish of the family Amiidae (Bowfins), which are currently found in southeastern Canada and the Eastern United States.

Partial vertebra of an Amiid Fish from the Eocene of Banks Island. Eberle et al. (2014).

The third specimen described is an isolated scale from an Esocid Fish (Pike), which are currently found across North America and in Eurasia from Western Europe to Siberia. A number of other Esocid scales were found, though only the best preserved is formally described in this paper.

Esocid Fish scale from the Eocene of Banks Island. Eberle et al. (2014).

Finally Eberle et al. describe a partial vertebra from a Crocodilian. The most cold tolerant modern Crocodilian, the American Alligator (Alligator mississippiensis) occurs naturally as far north as North Carolina, but numerous Crocodilian remains have been found in Eocene strata on Elesmere Island, suggesting that the Canadian High Arctic had a suitable climate for them close to the Eocene Thermal Maximum.

Vertebral centrum of an Eocene Crocodyliform from northern Banks Island. (A) Left lateral view; (B) dorsal view; (C) ventral view. Abbreviations: h, hypapophysis; ncs, neurocentral sutural surface; pc, posterior cotyle. Scale bar equals 5 mm. Eberle et al. (2014).

Taken together these fossils strongly imply that Banks Island probably had a climate similar to that of the Southern United States close to the Eocene Thermal Maximum. While this is no longer totally surprising, as we are now used to seeing such warm climate fossils from the Canadian High Arctic at this time, it does extend the known range of this ecosystem over 1100 km further to the west.

Thursday, 17 April 2014

Preserved wood from an Early Eocene kimberlite pipe in northwestern Canada’s Slave Province.

Kimberlite pipes are produced by rapid volcanic intrusions carrying magma from the Earth’s mantle rapidly to the surface, often resulting in explosive phreatomagmatic eruptions (explosions caused by hot magma coming into contact with water). These pipes are considered high value economic resources due to the common occurrence of diamonds within them. Surprisingly kimberlite pipes also often contain fossil material. This can come from two separate sources; organisms can fall directly into the erupting lava and be entombed within it as it cools (such intrusions of non-volcanic material, organic or otherwise, are known as xenoliths by volcanologists), alternatively material can be preserved in volcanic craters after the eruption, as organisms are buried in fine-grained volcanic ash and clay (volcanic maar), which has high preservational potential.

In a paper published in the journal PLoS One on 19 September 2012, Alexander Wolfe of the Department of Earth and Atmospheric Sciences at the University of Alberta, Adam Csank of the Environment and Natural Resources Institute at the University of Alaska, Anchorage, Alberto Reyes of the Department of Geoscience at the University of Wisconsin, Madison, Ryan McKellar also of the Department of Earth and Atmospheric Sciences at the University of Alberta, Ralf Tappert of the Institute of Mineralogy and Petrography at the University of Innsbruck and Karlis Muehlenbachs, again of the Department of Earth and Atmospheric Sciences at the University of Alberta, describe the discovery of a number of large wood fragments from the Panda Kimberlite Pipe, a volcanic intrusion which forms part of the Ekati diamond mining concession worked by BHP Billiton in Canada’s Great Slave Province, which has been calculated to be about 53.3 million years old (Early Eocene). The Panda Kimberlite Pipe forms part of the Lac de Gras Field, which contains about 150 such pipes, emplaced between 45 and 78 million years ago. The Panda Pipe is a simple 200 m diameter cylinder, apparently produced by a single eruption.

Wolfe et al. provide a detailed description of a single piece of wood, a large wood fragment which had fallen into the lava and been mummified. The wood is excellently preserved, with only the outermost millimetre having been fusinized (burned), suggesting an absence of free oxygen when it was entombed. The preserved structure of the wood allows the specimen to be assigned to a tree of the genus Metasequoia, a form of Giant Redwood now restricted to central China, but known to have been common in Alaska during the late Palaeocene and Early Eocene, and therefore not a great surprise in Slave Province.

(D) Fossil wood encrusted in olivine-rich volcaniclastic kimberlite. (E) Photograph of the specimen characterized in this study. The wood was split when removed from the ore, revealing a sliver of opaque amber (9.5 cm long by 0.5 cm wide) in the xylem. Wolfe et al. (2012).

Metasequoia requires a high level of humidity to survive, with a minimum of around 1000 mm of rainfall per year. The area where the fossil was recovered has around 280 mm of rainfall per year, suggesting that the climate was much wetter during the Early Eocene (it is possible that this 53 million year old specimen comes from a tree of the same species as the modern Chinese trees, since these are exceptionally long lived organisms). Since the tree was living close to the Paleocene-Eocene Thermal Maximum (about 55.5 million years ago), when the climate is predicted to have been substantially warmer and wetter in this region, this confirms the climatic predictions. Isotopic data obtained from both the cellulose of the wood and an amber (tree resin) inclusion within the fossil suggests that temperatures would have been around 7-12˚C warmer than at present while the tree was living, again tending to confirm the climatic predictions.

(F) RLS in transmitted light showing uniseriate and biseriate bordered pits and cross-fields. (G) TLS showing rays stacked 3–26 cells high. (H). SEM (TS) of ring boundary with earlywood (left) and latewood (right). (I) Close-up of tracheids in TS and calcite crystals within cells (arrows). J. Cross-section of ray with cross-field pits. (K and L) Close-ups of cross-field pits. (M) TLS close-up of rays. (N). Radial longitudinal section showing four contiguous rows of ray parenchyma cells with smooth end walls and no separation between the individual rows of cells. Wolfe et al. (2012).

Wednesday, 16 April 2014

Fossil Thrips from the Early Eocene of France.

Thrips (the term is both singular and plural) are tiny (usually less than 1 mm) Insects related to Lice and True Bugs. They have wings, but are poor flyers, and feed by sucking fluids from plant or animal hosts. Thrips do not undergo metamorphosis, the young are essentially smaller, non-reproducing versions of the adults. Due to their small size and ubiquitous nature, it is probable that Thrips are one of the larger Insect groups, though they are relatively understudied, with little work carried out on Thrips that do not have agricultural significance.

In a paper published in the journal Acta Palaeontologica Polonica on 19 December 2011, Patricia Nel of the Muséum national d'Histoire naturelle in Paris and AgroParisTech, Alexander Schmidt of the Courant Research Centre Geobiology at Georg−August−Universität Göttingen, Claus Bässler of the Nationalparkverwaltung Bayerischer Wald and André Nel, also of the Muséum national d'Histoire naturelle describe a new species of Thrips from Oise Amber, which originates from the early Eocene of the Paris Basin (about 53 million years old, close to the Paleocene–Eocene Thermal Maximum).

The new species is placed in the genus Uzelothrips, and given the species name eocenicus, meaning from the Eocene. The genus Uzelothrips has to date contained only a single species, the extant Uzelothrips scabrosus, which has been recorded from Brazil, Singapore, Australia and Angola. Uzelothrips eocenicus is almost identical to the modern species, differing only in the antennae, on which segments III and IV are fused in the modern species but separate in the Eocene one. The species is described from two specimens, one female and one of uncertain sex.

Macropterous specimen of Uzelothripid Insect Uzelothrips eocenicus, Lowermost Eocene, Le Quesnoy, Oise, France. (A) Dorsal view; inset: detail of antennal segments III and IV. (B) Drawings of right antennal segments III and IV in dorsal (B1) and ventral (B2) views. (C) Camera lucida drawing of in dorsal view. Nel et al. (2011).

Nel et al. also found a number of fungal fragments attached to one of the specimens. These are thought to be from a Sooty Mould, a type of fungus that primarily gains nutrients from the excreta of Aphids, Scale Insects etc. These have not previously been documented from Thrips, but examination of photographic records of Uzelothrips scabrosus showed that several specimens were in fact carrying similar Fungi.

Ascomycetes found attached to the cuticle of the fossil and extant Uzelothripid Insects. The small panels show higher magnification images of some fossil and extant fungi found at the locations indicated by the arrows. (A) Fossil apterous specimen of Uzelothrips eocenicus. The image is composed of photographs obtained from those optical sections which show the attached fungi most clearly. The arrowhead in the uppermost left panel indicates a Capnosporium−like conidium; the arrowhead in the middle right panel indicates a tapering hypha tip with dividing stage. (B) Recent specimen of Uzelothrips scabrosus. The asterisk refers to the elongated hypha that has possibly grown on the surface of the thrips after attachment. Nel et al. (2011).