Exceptional Fossil Preservation Research Articles

Organic geochemistry and paleoenvironment of the Early Eocene “Pesciara di Bolca” Konservat-Lagerstätte, Italy

Exceptional preservation of fossils in so-called Konservat-Lagerstätten requires specific depositional regimes excluding disturbance of bottom sediments by either wave actions and currents or by benthic fauna. We here describe a depositional model for the Eocene “Pesciara di Bolca” Konservat-Lagerstätte based on sedimentological, paleoecological, and detailed organic geochemical results. Sediments were deposited in a lagoonal-like basin with stagnant bottom waters located on an extended carbonate platform that was sheltered from open marine waters by a submarine threshold. Run-off from nearby land areas provided nutrients to support an algal community dominated by diatoms. No fossil diatom shells have been identified, but evidence for their presence is given by the high abundance of highly branched isoprenoids in extractable bitumens. Influx of terrigenous organic matter into the lagoon occurred in particular during deposition of the basal fish-bearing level L1. Here not only plant macrofossils, amber, spores and pollen but also the lipid composition indicated notable input of land plants via the presence of n-C 24 to n-C 32 carboxylic acids, long-chain n-alkanes ( n-C 27, n-C 29, n-C 31) and angiosperm wax triterpenoids. The redox regime in general was strongly reducing as evidenced by the high concentration of sulfur vs. organic carbon, excellent kerogen preservation as shown by high hydrogen indices, and low pristane/phytane but high phytane/ n-C 18 ratios. The water column was highly stratified with anoxic saline bottom and fresh surface waters. Euxinic conditions with free reduced sulfur present in the photic zone could only be detected in sediments from the L1 horizon via traces of aromatic carotenoids derived from green sulfur bacteria ( chlorobiaceae), which utilize H 2S in anoxygenic photosynthesis. The depositional regime is thus comparable to the lithographic limestones of Solnhofen but based on biomarker evidence lacks the high salinities postulated for the latter. Biomarker composition indicates that best preservation conditions prevailed in the basal part of the studied section (0–7 m above datum) but declined upon deposition of the upper part. We interpret the body of the Pesciara as a parasequence of the 4th order (0.01–0.5 Ma), with the lower part representing a relative sea-level lowstand and the upper part a relative sea-level highstand.

Benthic Paleoecology in the Givetian: An Example From the Kersadiou Formation (Massif Armoricain, NW France)

The Kersadiou Formation is well known for its exceptional preservation, diversity, and abundance of mid-Devonian marine fossils. A complete faunal inventory of the Kersadiou Formation over its entire outcrop area is presented here for the first time. Twelve complete sections have been thoroughly sampled from the 28 known outcrops in the Rade de Brest area. The detailed vertical and geographic distribution of 149 identified taxa, coupled with multivariate analyses, allows us to recognize three benthic brachiopod-dominated associations—the Holynetes, Ogorella, and Arcuaminetes associations. These associations reflect a progressive shallowing, which had been previously proposed based on lithological changes from the underlying Quelern Formation to the overlying Tibidy Formation. The corresponding environmental changes are from a protected or restricted marine environment, with a high diversity fauna (Holynetes association), to a shallower, open, higher-energy environment, characterized by a low-diversity assemblage (Arcuaminetes association); the Ogorella association occupies an intermediate position. While the three associations are well developed in the central and eastern parts of the Rade de Brest, only the Arcuaminetes association is well developed in the western outcrop area. This east-west distribution of faunas correlates with the paleoecological gradient evidenced in the studied area.

The “Preservation Paradox”: Microbes as a Key to Exceptional Fossil Preservation in the Kirkpatrick Basalt (Jurassic), Antarctica

Thin sedimentary interbeds within the Kirkpatrick Basalt (Jurassic) of Antarctica harbor exquisitely preserved ‘soft-bodied’ organisms that lived in and around shallow freshwater lakes of the time, some of which were hydrothermally influenced. In the hottest pools, associated with magmatic vents, unusual carbonates were apparently precipitated by Archaea extremophiles adapted to living near active lava flows. In cooler lakes more distant to the vents, fine siliciclastic sediments record other communities of spinicaudatan (“conchostracan”) and notostracan crustaceans, larval insects, fishes, and ostracodes much of which may have been sustained by microbial mats, which are also well preserved in the deposits. Along the lake-edge, carbonized leaves, peat or coal, and silicified logs are often found in association with paleosols. Notably, evidence of carnivory, a primary taphonomic filter, is essentially lacking in these sediments. Exceptional preservation of non-biomineralized or lightly skeletonized organisms, therefore, reflects the original diversity of non-biomineralized or lightly skeletonized organisms present.

Geobiology and the fossil record: eukaryotes, microbes, and their interactions

Geobiology attempts to understand the interactions between Earth and the life which has evolved on it. It is an all-encompassing field that embraces both living systems on Earth as well as an understanding of the history of these systems since life first evolved. The fossil record and associated geological and geochemical data provide a major avenue towards understanding the evolution of geobiological systems. Among the many new and exciting directions of research for geobiology, a particularly fertile field is represented by studies of the various interactions between eukaryotes and microbes that can be detected through examination of the fossil record. For example, such interactions include the various roles which microbes play in taphonomy and preservation of eukaryotes as fossils, particularly cases of exceptional fossil preservation. Similarly, recognition of microbially induced sedimentary structures (MISS) in siliciclastic sediments has been a subject of significant recent interest. Documentation of MISS has led to a greater understanding of the role of microbial mats in providing a distinctive structure to marine subtidal seafloors, which has fostered studies of benthic eukaryote adaptations to such mat-dominated environments. The continued evolution of bioturbation in the Cambrian led to elimination of microbial mats on shallow subtidal seafloors, causing evolutionary and ecological changes in eukaryotes adapted to living on and in seafloors structured by such mats. Studies of these changes, termed the “Cambrian substrate revolution”, have been documented for a variety of echinoderms, molluscs, and trace fossils, and are some of the first to illuminate ecological interactions between eukaryotes and microbes through study of the fossil record. This new awareness which geobiology represents has begun to produce a whole host of approaches that causes researchers in the laboratory of the molecular or microbiologist to interact with those from the laboratory of the geochemist as they are led on a field trip by the palaeontologist exploring some fundamental issue in the history of life. Such interactions are not only important for considerations of life on Earth, but provide a framework for the search for life that may have once existed on other planetary bodies, such as Mars. Data from deep time and hence the fossil record plays a central role in such research, and thus geobiology opens up vast new research opportunities for palaeontology.

Genesis of a locality of exceptional fossil preservation: paleoenvironments of Tepexi de Rodrı́guez (mid-Cretaceous, Puebla, Mexico)

This study of Tepexi de Rodrı́guez (Puebla, Mexico), a mid-Cretaceous (Aptian?) locality with exceptional fossil preservation, combines statistically based microfacies-transition analysis with spectral analysis of depth-series measurements, in an attempt to constrain the paleoenvironmental setting. Tepexi de Rodrı́guez (Tepexi) is largely composed of laminated micrites, and presents a complex amalgam of primary and diagenetically altered fabrics. Modified Markov analysis of microfacies successions was used to assess repetitive patterns among primary microfacies. The reconstructed microfacies succession indicates recurring upward-fining sequences. Spectral analysis of depth-series measurements of magnetic susceptibility and RGB visible color (redness) reveals a pattern of repetition in the sedimentary sequence that is concordant with patterns of Milankovitch cyclicity. Strong eccentricity, obliquity, and semi-precessional signals are inferred. This suite of Milankovitch cyclicities is attributed to double-monsoon influences on Tepexi from both the northern and southern hemispheres, and implies an average rock accumulation rate of 2.0 cm/kyr. Previous reconstructions of Tepexi (e.g. a variety of back-reef lagoonal settings) do not match the observations reported here. Likewise, tidally influenced deposition is ruled out. Tepexi de Rodrı́guez appears to have been an open marine basin with storm-dominated sedimentation and bottom waters with restricted circulation. The fossil biota has a strong terrestrial influence, indicating that land was close by.

Morphological data, extant Myriapoda, and the myriapod stem-group

The status of Myriapoda (whether mono-, para- or polyphyletic) and position of myriapods in the Arthropoda are controversial, an impediment to evaluating fossils that may be members of the myriapod stem-group. Parsimony analysis of 319 characters for extant arthropods provides a basis for defending myriapod monophyly and identifying those morphological characters that are necessary to assign a fossil taxon to the Myriapoda. The alliance of hexapods and crustaceans need not relegate myriapods to the arthropod stem-group; the Mandibulata hypothesis accommodates Myriapoda and Tetraconata as sister taxa. No known pre-Silurian fossils have characters that convincingly place them in the Myriapoda or the myriapod stem-group. Because the strongest apomorphies of Myriapoda are details of the mandible and tentorial endoskeleton, exceptional fossil preservation seems necessary to recognise a stem-group myriapod.

Unusual preservation of crustaceans and microbial colonies in a vadose zone, northwest Morocco

Exceptional fossil preservation is observed in self-sealing microcavities in limestones where lichens, cyanobacteria and fungi together entombed themselves and organic walled microfossils, crustaceans and their eggs. Preservation has been enabled by calcite coating, lining and impregnation of the exoskeleton of the crustaceans, which had a high original calcium content and acted as a nucleus for precipitation. The good preservation was facilitated by the microcavities, the surrounding limestone, the seasonality and rapidity of precipitation, the microbial colonies living on the specimens, and the fluxing of vadose waters through the karst. The microbes and the crustaceans probably became trapped by the very high rate of calcite precipitation promoted within the cavities. Entrapment in mucous-secreting mats of cyanobacteria and fungi preceded the destruction of some of the soft parts of the crustaceans. By the time the mats and the incorporated biota were sealed into the cavities in the limestone, the mucosic mats and their bacterial communities had mediated production of a range of calcite cements promoting preservation of the refractory tissues. This process has important implications for cementation studies in arid zones (and especially in the Martian subsurface), since a range of microbes are involved in progressive biomineralization leading to fossilization within a perched, vadose karst.

On the Chemical Purity of Marine Microfossils

As a paleontologist, I was pleased to see the 35-million-year-old shell of the planktonic foraminiferan Cribrohantkenina inflata grace the cover of Physics Today ( Physics Today 0031-9228 54 12 2001 16 https://doi.org/10.1063/1.1445530. December 2001; story on page 16 ). Calcium carbonate–secreting microfossils are a powerful proxy for estimating sea-surface temperature change through time using stable oxygen isotopes. Another challenge that biogeochemists and geoscientists face is the alteration of in vivo isotopic values by mineral and chemical changes after an organism’s death. Implicit in any isotopic analysis using calcite shells, or fossil mammal teeth, or even dinosaur bones, is the assumption that the original stable isotopes survived the passage of millions of years.A hemisphere away from the late Cretaceous marine localities of Paul Pearson’s work, 1 1. P. Pearson, et al. , Nature 413, 481 (2001). https://doi.org/10.1038/35097000 dinosaur bones lie buried in late Cretaceous clays above the Arctic Circle on the North Slope of Alaska. 2 2. W. A. Clemens, L. G. Nelms, Geology 21, 503 (1993). https://doi.org/10.1130/0091-7613(1993)021<0503:PIOATV>2.3.CO;2 They are so well preserved that an oil geologist in the 1960s originally identified them as the fossil remains of Ice Age mammals. A collection of those bones is cataloged in the University of California Museum of Paleontology. Under high magnification, the Alaska fossils reveal a beautifully preserved system of bone cells that are identical to the micron-scale architecture of a modern vertebrate bone. Similar to the Pearson group’s foraminifera, the dinosaur bones are entombed in clay sediments and do not appear altered by secondary remineralization or recrystallization. Microbeam particle-induced x-ray emission analysis revealed, however, that the bones showed significant postmortem enrichment by metals, primarily iron and manganese, more than 104 times greater than in the bones of modern crocodilians and birds (a dinosaur’s closest living relatives). 3 3. M. B. Goodwin, G. S. Bench, J. Vertebr. Paleontol. 20(3), 45A (2000). Clay surrounding the Alaska dinosaurs was also markedly enriched in these metals from the burial environment.Understandably, such factors are site specific and most likely vary by sediment layer and location. Their range and potential influence on a paleobiological isotopic signature remains largely unknown. Until that situation changes, the potential alteration of stable isotope values in fossil shells, bones, and teeth prevents the rejection of the null hypothesis that all fossil material is altered.Beauty is in the eye of the beholder, and exceptional fossil preservation, even at the micron level, does not guarantee pristine chemistry.REFERENCESSection:ChooseTop of pageREFERENCES <<CITING ARTICLES1. P. Pearson, et al. , Nature 413, 481 (2001). https://doi.org/10.1038/35097000 , Google ScholarCrossref2. W. A. Clemens, L. G. Nelms, Geology 21, 503 (1993). https://doi.org/10.1130/0091-7613(1993)021<0503:PIOATV>2.3.CO;2 , Google ScholarCrossref3. M. B. Goodwin, G. S. Bench, J. Vertebr. Paleontol. 20(3), 45A (2000). Google Scholar© 2002 American Institute of Physics.

Primitive deuterostomes from the Chengjiang Lagerstätte (Lower Cambrian, China).

Cambrian fossil-Lagerstätten (sites of exceptional fossil preservation), such as those from Chengjiang (Lower Cambrian) and the Burgess Shale (Middle Cambrian), provide our best window into the Cambrian 'explosion'. Such faunas are known from about 40 localities, and have yielded a widely disparate series of taxa ranging from ctenophores to agnathan fish. Recent excavations of the Chengjiang fossil-Lagerstätte, known from a series of sites near Kunming in Yunnan, south China, have resulted in the discovery of several new forms. In conjunction with material described earlier, these provide evidence for a new group of metazoans, the vetulicolians. Several features, notably a series of gill slits, suggest that this group can throw light on an early stage of deuterostome diversification.

The Chengjiang Biota: Record of the Early Cambrian Diversification of Life and Clues to Exceptional Preservation of Fossils

The Chengjiang Biota: Record of the Early Cambrian Diversification of Life and Clues to Exceptional Preservation of Fossils

Self-sedimented diatom mats as agents of exceptional fossil preservation in the Oligocene Florissant lake beds, Colorado, United States

Self-sedimented diatom mats as agents of exceptional fossil preservation in the Oligocene Florissant lake beds, Colorado, United States

Self-sedimented diatom mats as agents of exceptional fossil preservation in the Oligocene Florissant lake beds, Colorado, United States

Research Article| March 01, 2000 Self-sedimented diatom mats as agents of exceptional fossil preservation in the Oligocene Florissant lake beds, Colorado, United States Ian C. Harding; Ian C. Harding 1School of Ocean and Earth Science, University of Southampton, European Way, Southampton SO14 3ZH, UK Search for other works by this author on: GSW Google Scholar Loraine S. Chant Loraine S. Chant 1School of Ocean and Earth Science, University of Southampton, European Way, Southampton SO14 3ZH, UK Search for other works by this author on: GSW Google Scholar Author and Article Information Ian C. Harding 1School of Ocean and Earth Science, University of Southampton, European Way, Southampton SO14 3ZH, UK Loraine S. Chant 1School of Ocean and Earth Science, University of Southampton, European Way, Southampton SO14 3ZH, UK Publisher: Geological Society of America Received: 19 Jul 1999 Revision Received: 26 Oct 1999 Accepted: 04 Nov 1999 First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2000) 28 (3): 195–198. https://doi.org/10.1130/0091-7613(2000)28<195:SDMAAO>2.0.CO;2 Article history Received: 19 Jul 1999 Revision Received: 26 Oct 1999 Accepted: 04 Nov 1999 First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Ian C. Harding, Loraine S. Chant; Self-sedimented diatom mats as agents of exceptional fossil preservation in the Oligocene Florissant lake beds, Colorado, United States. Geology 2000;; 28 (3): 195–198. doi: https://doi.org/10.1130/0091-7613(2000)28<195:SDMAAO>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Microbial mats play a major role in the formation of exceptionally preserved fossil deposits by overgrowing and binding organic remains and sedimentary particles. This minimizes hydrodynamic and biological disruption of dead organisms and sedimentary laminae, but published works all implicate prokaryotic cyanobacteria as the microbial agent. However, exceptionally well preserved macrofossils of the Oligocene Florissant lake beds (Colorado, United States) are enveloped in matted aggregations of mucous-secreting, pennate diatom frustules. It is suggested that the macrobiota became entrapped in mucous-secreting mats of surface water blooms of planktonic diatoms in lake Florissant. As the mats and the incorporated macrobiota were sedimented out of the water column, the mucosic mats and their associated bacterial communities arrested decay and promoted preservation of refractory tissues. Thus, by a completely different mechanism, the diatom mats fulfilled the same preservational role previously suggested for cyanobacterial mats. This hitherto unrecognized mode of preservation may be an important causative factor in the formation of exceptionally preserved lacustrine fossil biotas. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

A pipiscid-like fossil from the Lower Cambrian of south China

Exceptional fossil preservation is critical to our understanding of early metazoan evolution. A key source of information is the Burgess Shale-type faunas1,2,3,4,5. Fossils from these deposits provide important insights into metazoan phylogeny, notably that of stem-group protostomes2,3,6, and related topics such as trophic specialization7. Metazoan relationships are also being significantly reappraised in terms of molecular-based phylogenies8,9, but integration of these data with palaeontological systematics is not straightforward10,11. Moreover, molecular phylogenies are silent concerning the anatomies of stem-groups and the functional transitions that underpin the origin of different body plans2,6. Some hitherto enigmatic fossils possess unique character–state combinations that, although they can be shoe-horned into extinct phyla12, may be more profitably interpreted as defining major stem-groups2,3. Here we describe a possible pipiscid, a metazoan previously known only from the Upper Carboniferous13,14, from the Lower Cambrian of south China. Pipiscids are currently interpreted as being agnathan chordates13,14,15, but this discovery from the Chengjiang fossil-Lagerstatte indicates that the assignment of pipiscids to the Agnatha deserves to be reconsidered.

Bioimmuration: exceptional fossil preservation made routine

Bioimmuration, broadly defined as fossilization by virtue of organic overgrowth, allows preservation of soft-bodied organisms and soft parts of organisms with mineralized skeletons. Sessile organisms attached to hard or firm substrates are routinely overgrown by other organisms competing for living space. If the overgrowing organism has a mineralized skeleton which is likely to be fossilized, then it may carry a high fidelity (sub-micron scale) impression of the overgrown organism on its underside. This is a mould bioimmuration, the simplest mode of preservation. A diagenetic infilling of the mould, commonly by calcite, produces a cast bioimmuration. In addition, the protected microenvironment between the overgrowing organism and the substratum favours early diagenetic permineralization of the soft tissues of the bioimmured organism and the development of more complex preservational styles.In spite of its potential for soft part fossilization, very little research has been undertaken on bioimmuration, with the notable exception of the work of Ehrhard Voigt principally on Maastrichtian sea-grass communities. Research in progress is revealing a great abundance of bioimmured fossils in Mesozoic shallow marine deposits of NW Europe where oysters and serpulids overgrew a variety of other organisms.Bioimmured soft-bodied bryozoans belonging to the Order Ctenostomata are very common and display a range of preservational styles. Minute spines and pores ornamenting the cuticular zooidal walls are sometimes present, as are permineralized pore chambers. The high diversity of stoloniferan and carnosan ctenostomes encrusting hard substrates in the Oxfordian and Kimmeridgian is striking and contrasts with the depauperate fauna of calcified cyclostome bryozoans.Oyster shells in the Kimmeridge Clay are often encrusted by myriads of tiny individuals of the inarticulate brachiopod Discinisca, previously known from comparatively few specimens of this age. Emerging from the fragile commissures are setae several times the length of the delicate phosphatic shells. Setae of neighbouring individuals may be aligned in parallel facing away from the direction of approach of the overgrowing organism.The hemichordate Rhabdopleura is common as a bioimmured fossil in the Oxford Clay. Overgrowth protects the periderm and the black stolons, and colonies are much more intact than previously described examples of this genus from the Jurassic.The Phylum Entoprocta had no unequivocal fossil record before the recent discovery of bioimmured entoprocts in the Kimmeridge Clay. Colonies comprise stolons linking erect zooids which have been pushed flat against the substratum during overgrowth. The existence of thickened sockets at the base of the zooids permits assignment of the fossils to the extant genus Barentsia. Permineralization of the entoproct cuticle has occurred, leaving minute pores apparently once occupied by epithelial microvilli.Pedunculate barnacles are commonly found bioimmured by oysters in the mid-Cretaceous Cambridge Greensand. Normally the cirri are retracted but in one exceptional example their outlines are clearly visible as moulds on the attachment area of an oyster.

Exceptional preservation of fossils in an Upper Proterozoic shale.

Late Proterozoic organisms must have been diverse and widely distributed, but in general their fossil record is both taxonomically and environmentally limited. Exceptional preservation of Proterozoic fossils is not unknown, but it is usually associated with silicified carbonates from restricted peritidal or playa lake environments. We report here an exceptionally well preserved and distinctive assemblage of Late Proterozoic fossils from subtidal marine shales. In addition to the sphaeromorphic acritarchs and cyanobacterial sheaths routinely preserved in Proterozoic rocks, this assemblage includes multicellular algae ('seaweeds'), a diverse assortment of morphologically complex protistan vesicles, and probable heterotrophic bacteria. Thus, it provides one of the clearest and most taxonomically varied views of Proterozoic life yet reported.

Konservat-Lagerstätten:cause and classification

A review of the processes required for exceptional preservation of soft-bodied fossils demonstrates that anoxia does not significantly inhibit decay and emphasizes the importance of early diagenetic mineralization. Early diagenesis is the principal factor amongst the complex processes leading to soft-part preservation. The development of a particular preservational mineral is controlled by rate of burial, amount of organic detritus, and salinity. A new causative classification of soft-bodied fossil biotas is presented based upon fossil mineralogy and mineral paragenesis.

Taphonomy of Middle Pennsylvanian Mazon Creek Area Fossil Localities, Northeast Illinois: Significance of Exceptional Fossil Preservation in Syngenetic Concretions

Mazon Creek area fossil localities (Pennsylvanian: Westphalian D) in northeast Illinois provide an extraordinary preservational window for the study of Late Paleozoic terrestrial, fresh-water, and estuarine marine organisms. Marine animals were killed by episodic pulses of turbidfresh water associated with floodingfrom distributaries, and terrestrial organisms were introduced into coastal waters from upstream sources. Rapid burial entombed remains, commonly before significant decomposition had occurred, and very early diagenesis ensured fossil preservation as molds and composite impressions within sideritic concretions. The taphonomy of these deltaic, fossil-bearing beds is complex. Episodic engulfment of organisms is indicated by animal escape activity and by the presence of upended plant fragments. Numerous, distinctive, cyclic repetitions of siltstone-claystone laminae, each recording a single tidal (flood-ebb) event, are observed in areas yielding marine organisms; these indicate that rapid but extremely regular deposition was also important. Concretion formation was probably influenced, but not necessarily triggered, by decay processes. Siderite precipitation reflects three key conditions: the availability of iron, rapid burial of organic material, and a low to nonexistent supply of sea-water sulfate to centers of interstitial microbial activity. A regional (seaward) decrease in the quality offossil preservation is observed away from the coastal depocenter, and an interval of sparsely fossiliferous facies (a taphonomic discontinuity) occurs between the delta complex and shell-rich, normal marine deposits. The preservational significance of early diagenetic siderite is discussed; we argue that paleoenvironmental interpretations of analogous or similar nearshore deposits lacking fossiliferous concretions must be made cautiously. The potential value of Mazon Creek-type facies in the study of other Pennsylvanian nearshore deposits, including many superficially barren shales, is stressed. The association of the fossilbearing concretions with inferred estuarine-deltaic facies points to the need for future actualistic studies of comparable modern coastal environments.