Extensive primary production promoted the recovery of the Ediacaran Shuram excursion

Member IV of the Ediacaran Doushantuo Formation records the recovery from the most negative carbon isotope excursion in Earth history. However, the main biogeochemical controls that ultimately drove this recovery have yet to be elucidated. Here, we report new carbon and nitrogen isotope and concentration data from the Nanhua Basin (South China), where δ13C values of carbonates (δ13Ccarb) rise from − 7‰ to −1‰ and δ15N values decrease from +5.4‰ to +2.3‰. These trends are proposed to arise from a new equilibrium in the C and N cycles where primary production overcomes secondary production as the main source of organic matter in sediments. The enhanced primary production is supported by the coexisting Raman spectral data, which reveal a systematic difference in kerogen structure between depositional environments. Our new observations point to the variable dominance of distinct microbial communities in the late Ediacaran ecosystems, and suggest that blooms of oxygenic phototrophs modulated the recovery from the most negative δ13Ccarb excursion in Earth history.

Hermann Löns’ “Quintär” – an early approach to the geological stratigraphy of the Age of Humans and its significance in geosciences

In 1908, Hermann Löns outlined the concept of a Quintär” (“Quintary period”) to describe geological and biological manifestations of the Age of Humans. His definition of the “Quintary” consisted of twocomponents: a lithostratigraphical (“Quintary deposits” or “Quintary stratum”), and a faunistic (“Quintary fauna”) one. With a view on the stratigraphical component, Löns already anticipated the approach of the 21st Century to establish a geological definition for the Age of Humansbased on physical manifestations and geological evidence, that is nowadays reflected in the attempts to define the anthropocene. Transposed into modern terminology, the “Quintary stratum” is definedas a lithostratigraphical unit (Quintary Lithosome), that contains all deposits in which non-anthropogenic sedimentary processes have been replaced or modified by anthropogenic or technogenic activity. The Quintary Lithosome has a diachronous base and intercalates in its lower part vertically and laterally with non-anthropogenic deposits of the Holocene Series. The upper part, that correlates with the anthropocene series, has a global distribution. The Quintary Lithosome is exclusively defined for geological stratigraphies on Earth. It widely – though not totally – overlaps with the archaeosphere as a partial equivalent in archaeological stratigraphy. Previous suggestions to redefine the mostrecent period of Earth history by adopting a biostratigraphical scheme based on hominids and their cultural manifestations, are rejected hereinfor the realm of geological stratigraphy. However, for the context of archaeological stratigraphy, it is suggested to define the phase of cultural manifestations of hominins and their corresponding deposits as the Anthropian age and deposits, respectively.

Franz Unger and plant evolution: Representations of plants through time

ABSTRACT This chapter will highlight a series of lithographs produced by Franz Unger and Josef Kuwasseg that emphasize how Unger used plants to represent different periods of earth history. While Henry De la Beche is credited with the first depiction of ancient life through art (Duria antiquior), Unger’s work was the first to illustrate how plants could be used as indicators of changes in life history. In collaboration with artist Josef Kuwasseg, he embarked on a project entitled The Primitive World in Its Different Periods of Formation that consisted of 14 lithographs that were published in 1851. The title was unique in that it combined the concepts of a “primitive world,” or the widely accepted contemporary idea of undifferentiated deep time, with our modern concept of different periods of earth history. Unger selected periods for this project based upon major strata, but his botanical roots led him to emphasize the importance of plants in each lithograph. The series begins with the “Transition Period,” or the strata that contain the most fossil evidence to develop a reconstruction, and ends with a depiction of the arrival of man in a plant-filled world. This series of lithographs offers a unique contribution to the history and philosophy of geology as Unger recognized the importance of plants to our understanding of geology and deep time in the nineteenth century.

The illustrations of Brongniart and Cuvier illuminate paleontology in the early nineteenth century

ABSTRACT The concept of biostratigraphy was a significant step in the evolution of geoscience. Alexandre Brongniart (1770–1847) and Georges Cuvier (1769–1832) were key contributors to developing the subdiscipline as they worked to decode the stratigraphy of the Paris Basin in the first decades of the nineteenth century. Their illustrations of fossils, local geologic columns, and a regional geologic map played a decisive role in furthering an understanding of the value of paleontology in the service of illuminating Earth history.

Significance of the suture line in cephalopod taxonomy revealed by 3D morphometrics in the modern nautilids Nautilus and Allonautilus

Assessing the taxonomic importance of the suture line in shelled cephalopods is a key to better understanding the diversity of this group in Earth history. Because fossils are subject to taphonomic artifacts, an in-depth knowledge of well-preserved modern organisms is needed as an important reference. Here, we examine the suture line morphology of all known species of the modern cephalopods Nautilus and Allonautilus. We applied computed tomography and geometric morphometrics to quantify the suture line morphology as well as the conch geometry and septal spacing. Results reveal that the suture line and conch geometry are useful in distinguishing species, while septal spacing is less useful. We also constructed cluster trees to illustrate the similarity among species. The tree based on conch geometry in middle ontogeny is nearly congruent with those previously reconstructed based on molecular data. In addition, different geographical populations of the same species of Nautilus separate out in this tree. This suggests that genetically distinct (i.e., geographically isolated) populations of Nautilus can also be distinguished using conch geometry. Our results are applicable to closely related fossil cephalopods (nautilids), but may not apply to more distantly related forms (ammonoids).

Climate Change and Marine Geological Dynamics

The tendency for climate to change has been one of the most surprising outcomes of the study of Earth history [...]

Weathering controls on the Phanerozoic phosphate cycle

Although phosphate is an essential macronutrient for marine biota, critical to our understanding of marine productivity, biogeochemistry, and evolution, its long-timescale geologic history is poorly constrained. We constrain weathering-derived fluxes and seawater concentrations of phosphate throughout the Phanerozoic (541 Ma to present), by developing a model for the coupled, long-term biogeochemical cycles of phosphate, carbon, oxygen, and calcium. We find that the relative contribution of continental and seafloor weathering to the total weathering rate exerts a first-order control on ocean productivity, through a previously uninvestigated mechanism. Specifically, continental weathering is a source of the limiting nutrient phosphate, but seafloor weathering is not. As a result, times in Earth history in which seafloor weathering constitutes a large fraction of the total weathering rate (e.g., the early Paleozoic and Mesozoic), are also times in which phosphate delivery to the ocean is relatively low. A lower concentration of phosphate in seawater likely affected primary productivity, oceanic and atmospheric oxygen concentrations, with possible implications for the evolution of marine fauna over Earth history.