OOIMMURATION: ENHANCED FOSSIL PRESERVATION BY OOIDS, WITH EXAMPLES FROM THE MIDDLE JURASSIC OF SOUTHWESTERN UTAH, USA

Palaios ◽  
2021 ◽  
Vol 36 (10) ◽  
pp. 326-329
Author(s):  
MARK A. WILSON ◽  
ANNA M. COOKE ◽  
SHELLEY A. JUDGE ◽  
TIMOTHY J. PALMER
Keyword(s):  
Middle Jurassic ◽  
Depositional Environments ◽  
Fossil Assemblages ◽  
Fossil Preservation

ABSTRACT Ooimmuration is here defined as a taphonomic process by which fossils are preserved within ooids. It is a form of lithoimmuration, although depending on the role of microbes in the formation of the ooid cortex, ooimmuration can also be considered a type of bioimmuration. Fossils enclosed within ooids are protected from bioerosion as well as the abrasion common in energetic depositional environments such as ooid shoals. Many taxa in some fossil assemblages may be known only because they were ooimmured. We describe as examples of ooimmuration fossils preserved in an oolite from the Middle Jurassic (Bajocian) Carmel Formation in southwestern Utah.

LITHOLOGICAL AND PALEOCOMMUNITY VARIATION ON A MISSISSIPPIAN (TOURNAISIAN) CARBONATE RAMP, MONTANA, USA

Palaios ◽  
2021 ◽  
Vol 36 (3) ◽  
pp. 95-114
Author(s):  
GARETT M. BROWN
Keyword(s):  
Cluster Analysis ◽  
Environmental Gradients ◽  
Depositional Environments ◽  
Third Order ◽  
Depositional Sequence ◽  
Heterogeneous Distribution ◽  
Point Count ◽  
Sediment Types ◽  
Fossil Assemblages ◽  
Replicate Sampling

ABSTRACT The ecological structure of ancient marine communities is impacted by the environmental gradients controlling assemblage compositions and the heterogeneous distribution of sediment types. Closely spaced, replicate sampling of fauna has been suggested to mitigate the effects of such heterogeneity and improve gradient analyses, but this technique has rarely been combined with similar sampling of lithologic data. This study analyses lithological and faunal data to determine the environmental gradients controlling the composition of Mississippian fossil assemblages of the lower Madison Group in Montana. Eighty-one lithological and faunal samples were collected from four stratigraphic columns in Montana, which represent the deep-subtidal, foreshoal, and ooid-shoal depositional environments within one third-order depositional sequence. Cluster analysis identifies three distinct lithological associations across all depositional environments—crinoid-dominated carbonates, peloidal-crinoidal carbonates, and micritic-crinoidal carbonates. Cluster analysis and nonmetric multidimensional scaling (NMS) identifies a highly diverse brachiopod biofacies and a solitary coral-dominated biofacies along an onshore-offshore gradient. Carbonate point count data and orientation of solitary corals indicate that substrate and wave energy are two potential variables that covary with the onshore-offshore gradient. Overlaying lithological information on the NMS indicates a secondary gradient reflecting oxygen that is expressed by increasing bioturbation and gradation from brown to dark gray carbonates to medium-light gray carbonates. Taken together, these findings demonstrates how combining closely spaced, replicate sampling of lithologic and faunal data enhances multivariate analyses by uncovering underlying environmental gradients that control the variation in fossil assemblages.

scholarly journals Exceptional preservation of reproductive organs and giant sperm in Cretaceous ostracods

2020 ◽  
Vol 287 (1935) ◽  
pp. 20201661
Author(s):  
He Wang ◽  
Renate Matzke-Karasz ◽  
David J. Horne ◽  
Xiangdong Zhao ◽  
Meizhen Cao ◽  
...  
Keyword(s):  
Reproductive Organs ◽  
Depositional Environments ◽  
Ct Reconstruction ◽  
Origin And Evolution ◽  
Exceptional Preservation ◽  
Morphological Adaptations ◽  
Single Piece ◽  
Evolutionary Success ◽  
Fossil Preservation ◽  
A New Species

The bivalved crustacean ostracods have the richest fossil record of any arthropod group and display complex reproductive strategies contributing to their evolutionary success. Sexual reproduction involving giant sperm, shared by three superfamilies of living ostracod crustaceans, is among the most fascinating behaviours. However, the origin and evolution of this reproductive mechanism has remained largely unexplored because fossil preservation of such features is extremely rare. Here, we report exceptionally preserved ostracods with soft parts (appendages and reproductive organs) in a single piece of mid-Cretaceous Kachin amber (approximately 100 Myr old). The ostracod assemblage is composed of 39 individuals. Thirty-one individuals belong to a new species and genus, Myanmarcypris hui gen. et sp. nov., exhibiting an ontogenetic sequence from juveniles to adults (male and female). Seven individuals are assigned to Thalassocypria sp. (Cypridoidea, Candonidae, Paracypridinae) and one to Sanyuania sp. (Cytheroidea, Loxoconchidae). Our micro-CT reconstruction provides direct evidence of the male clasper, sperm pumps (Zenker organs), hemipenes, eggs and female seminal receptacles with giant sperm. Our results reveal that the reproduction behavioural repertoire, which is associated with considerable morphological adaptations, has remained unchanged over at least 100 million years—a paramount example of evolutionary stasis. These results also double the age of the oldest unequivocal fossil animal sperm. This discovery highlights the capacity of amber to document invertebrate soft parts that are rarely recorded by other depositional environments.

Compositions, sources and depositional environments of organic matter from the Middle Jurassic clays of Poland

2007 ◽  
Vol 22 (11) ◽  
pp. 2456-2485 ◽  
Author(s):  
Leszek Marynowski ◽  
Michał Zatoń ◽  
Bernd R.T. Simoneit ◽  
Angelika Otto ◽  
Mariusz O. Jędrysek ◽  
...  
Keyword(s):  
Organic Matter ◽  
Middle Jurassic ◽  
Depositional Environments

scholarly journals SMALL SHELLY FOSSIL PRESERVATION AND THE ROLE OF EARLY DIAGENETIC REDOX IN THE EARLY TRIASSIC

Palaios ◽  
2018 ◽  
Vol 33 (10) ◽  
pp. 441-450 ◽  
Author(s):  
SARA B. PRUSS ◽  
NICHOLAS J. TOSCA ◽  
COURCELLE STARK
Keyword(s):  
Early Triassic ◽  
Fossil Preservation

scholarly journals A Pleistocene palaeovegetation record from plant wax biomarkers from the Nachukui Formation, West Turkana, Kenya

2016 ◽  
Vol 371 (1698) ◽  
pp. 20150235 ◽  
Author(s):  
Kevin T. Uno ◽  
Pratigya J. Polissar ◽  
Emma Kahle ◽  
Craig Feibel ◽  
Sonia Harmand ◽  
...  
Keyword(s):  
Carbon Isotope ◽  
Lacustrine Sediments ◽  
Archaeological Site ◽  
Depositional Environments ◽  
Major Transitions ◽  
Turkana Basin ◽  
Isotope Data ◽  
Wide Range ◽  
Plant Wax

Reconstructing vegetation at hominin fossil sites provides us critical information about hominin palaeoenvironments and the potential role of climate in their evolution. Here we reconstruct vegetation from carbon isotopes of plant wax biomarkers in sediments of the Nachukui Formation in the Turkana Basin. Plant wax biomarkers were extracted from samples from a wide range of lithologies that include fluvial–lacustrine sediments and palaeosols, and therefore provide a record of vegetation from diverse depositional environments. Carbon isotope ratios from biomarkers indicate a highly dynamic vegetation structure ( ca 5–100% C 4 vegetation) from 2.3 to 1.7 Ma, with an overall shift towards more C 4 vegetation on the landscape after about 2.1 Ma. The biomarker isotope data indicate ca 25–30% more C 4 vegetation on the landscape than carbon isotope data of pedogenic carbonates from the same sequence. Our data show that the environments of early Paranthropus and Homo in this part of the Turkana Basin were primarily mixed C 3 –C 4 to C 4 -dominated ecosystems. The proportion of C 4 -based foods in the diet of Paranthropus increases through time, broadly paralleling the increase in C 4 vegetation on the landscape, whereas the diet of Homo remains unchanged. Biomarker isotope data associated with the Kokiselei archaeological site complex, which includes the site where the oldest Acheulean stone tools to date were recovered, indicate 61–97% C 4 vegetation on the landscape. This article is part of the themed issue ‘Major transitions in human evolution’.

Echinoderm taphonomy, taphofacies, and Lagerstätten

1997 ◽  
Vol 3 ◽  
pp. 147-190 ◽  
Author(s):  
Carlton E. Brett ◽  
Heather A. Moffat ◽  
Wendy L. Taylor
Keyword(s):  
Benthic Communities ◽  
High Energy ◽  
Depositional Environments ◽  
Plate Boundaries ◽  
Bedding Planes ◽  
Short Period ◽  
Characteristic Modes ◽  
Fossil Preservation ◽  
Type 3

Taphonomic study of echinoderms provides useful information on sedimentary conditions before, during, and after burial. Taphonomic studies of Recent echinoderms indicate that much skeletal disarticulation occurs within a few days after death. However, experiments also indicate that within a short period after death echinoderm carcasses remain rather resistant to disarticulation, and thus may be transported a considerable distance by currents; following periods of a few hours of decay, more delicate portions of echinoderm skeletons are readily disarticulated. Some skeletal modules (e.g., crinoid pluricolumnals) may resist disarticulation for periods of months in quiet- and or cool-water environments. Anoxia promotes intact preservation by excluding scavenging metazoans. Echinoderm ossicles may undergo minor abrasion and/or corrosion if left exposed, and less dense stereom corrodes much more rapidly than dense plates, such as echinoid spines. However, heavily abraded ossicles may indicate prefossilization and reworking.Various groups of echinoderms (e.g., pelmatozoans, asterozoans, echinoids) have differing propensities for degradation and, therefore, produce different arrays of preserved fossil material primarily depending upon the relative rates of burial, bottom-water oxygenation, and turbulence. Echinoderms may be divided into three groups based upon the relative ease of skeletal disarticulation. Type 1 echinoderms include weakly articulated forms (e.g., asteroids and ophiuroids) that rapidly disintegrate into individual ossicles. Type 2 includes those echinoderms whose bodies contain portions in which are more tightly sutured, as well as portions in which the ossicles are somewhat more delicately bound (e.g., crinoids, regular echinoids). Such echinoderms display more varied taphonomic grades from fully intact to mixtures of isolated ossicles and articulated modules. Type 3 comprises those echinoderms (e.g., irregular echinoids) in which major portions of the skeleton are so resistant to disarticulation that they may be broken across sutures rather than coming apart at plate boundaries.Comparative taphonomy of particular types of echinoderm skeletal remains leads to recognition of distinctive taphofacies that characterize particular depositional environments. Taphofacies include two types of characteristic modes of fossil preservation: event taphonomic signatures and background taphonomic signatures. Depending upon normal conditions of environmental energy and rates of sedimentation, the background condition of various types of echinoderms for a given facies may range from articulated, unabraded skeletal modules (in Types 2 and 3) to highly corroded and/or abraded ossicles. Conversely, the occurrence of fully intact fossil echinoderms provides unambiguous evidence of rapid and deep burial of benthic communities. Such well-preserved fossil assemblages can provide a wealth of information regarding the paleobiology of echinoderms, as well as the nature of the depositional events and burial histories.This paper presents a preliminary classification and characterization of background and event aspects of echinoderm taphofacies for carbonate- (9 taphofacies, including reefs and hardgrounds) and siliciclastic-dominated (5 taphofacies) environments. In each case, we recognize a spectrum of echinoderm taphofacies that coincides with a gradient of environments, ranging from nearshore, high energy shoreface through proximal and distal storm-influenced shelf, to deeper ramp and dysoxic basinal settings. Most taphofacies also feature particular styles of obrution (smothered bottom) Lagerstätten. These range from scattered lenses of articulated fossils in some high energy sandstone and grainstone facies to bedding planes of articulated, pyrite coated specimens in dark shales. We classify and discuss the genesis of these types of Lagerstätten and list typical examples. Finally, we present a simple model that integrates the occurrence of various echinoderm taphofacies with concepts of cyclic and sequence stratigraphy.

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