Planktonic foraminifera tests can suffer dissolution, which usually involves partial damage, weight loss, and fragmentation. Since planktonic foraminifera assemblages, consisting of different resistant/susceptible species, can be strongly modified by dissolution, it is imperative to quantify its effect. The fragmentation index proposed 50 years ago has been used widely to measure preservation of planktonic foraminifera tests, but calibrations to this method are necessary. Some revisions are based on assumptions, like a certain number of fragments produced by a unique test, which is then used to compare whole tests with the dissolution remains. Likewise, researchers do not agree on what they count and how they identify what they count. Here we present a standardized and less subjective method, called fragmentation intensity (FI), to better assess the fragmentation of planktonic foraminifera through image software analysis, which includes both fragmentation remains (fragments and broken tests) and their measured area and perimeter. When compared to calcium carbonate content, grain sand content, and planktonic foraminifera tests per gram of dry sediment, the FI method derived better correlation values than the broken and fragments indexes. Future studies, in varying oceanographic contexts, can test this method to improve confidence, and eventually possibly adapt the index into a proxy for calcium carbonate undersaturation.

The Paleozoic evolution of vegetation transformed terrestrial landscapes, facilitating novel sedimentary processes and creating new habitats. This transformation left a permanent mark on the sedimentary record, perhaps most strikingly via an upsurge in preserved terrestrial mudrock. Whereas feedbacks between evolving vegetation and river structure have been widely studied, Paleozoic estuaries have so far received scant attention. Located at the interface between the land and sea, the co-adjustment of estuarine morphology and plant traits are fundamentally tied to a varied range of geochemical cycles, and determine how global silicate weathering patterns may have varied over time. Here we employ an eco-morphodynamic model with an in-built vegetation code to simulate estuarine morphology through five key stages in plant evolution. An abiotic model (early Precambrian?) saw mud deposition restricted to fortuitous instances of limited erosion along bar-flanks. Estuaries colonized by microbial mats (Precambrian onwards) facilitated mud accretion that sufficiently stabilized bar surfaces to promote extensive mudflat development. Small-stature, rootless vegetation (Silurian–Early Devonian) introduced novel above-ground baffling effects which led to notable mud accumulation in lower-energy environments. The incorporation of roots (Early Devonian) strengthened these trends, with root structures decreasing the mortality of the occupying plants. Once the full complement of modern vascular plant architectures had evolved (Middle Devonian), dense colonization promoted the formation of in-channel islands accompanied with system-wide mud accumulation. These simulations suggest estuaries underwent profound change during the Paleozoic, with the greening of the continents triggering processes and feedbacks which render all previous source-to-sink sediment pathways non-uniformitarian.

The Fonseca Formation (Eocene–Oligocene boundary, Minas Gerais, Brazil) is well known for its paleoflora, especially of flowering plants. The richness of this insect-bearing fossil locality is significantly less well understood, but we can shed light on the insect paleocommunity. One hundred and eight fossil insect specimens were examined and separated into four grades based on their preservational quality. We conducted analyses of taphonomic features, including body orientation, size, articulation, and chemical composition. Our results reveal differences in the body articulation of the insects. The fully articulated specimens apparently did not experience extensive flotation time at the water-air interface, whereas for partially articulated and disarticulated specimens the opposite is true. These taphonomic features would be acquired during the biostratinomy stage, and not early diagenesis. We also employed high resolution techniques (SEM-EDS and Raman spectroscopy) to understand their fossilization potential. Our chemical data suggest that the Fonseca insects are preserved as organic remains in carbonaceous compressions. Thus, chitin biomolecules most likely were transformed into more resistant biopolymers during diagenesis. This interpretation may also imply that the carbonaceous material originated from the insect itself. In this study, we document new discoveries and also provide future prospects for study of the Fonseca Formation.