Abstract The preservation and accretion rates of fluvial meander-belt deposits appear to vary with the time over which they are evaluated, but the drivers of this effect are not fully understood. Using channel trajectories tracking the temporal evolution of meandering rivers, constrained with data on past river planforms, a numerical model is used to simulate planform evolutions of meander-belt reaches that underwent different types of meander transformation behaviours and bend cutoffs. Sediment preservation and bar accretion rates are quantified for three hierarchies of depositional products: (i) accretion stages reflecting intervals of bend migration by a certain meander-transformation style, (ii) meander-belt segments encompassing multiple stages but no bend cutoffs and (iii) meander-belt segments that experienced one or multiple cutoffs. Results show that distinct power-law relationships between the accretion rate and the time of sedimentation exist for river systems of different magnitudes in scale. Within each order of magnitude in river-system size, a single power-law relationship fails to effectively capture all depositional hierarchies. Sediment preservation varies with the time over which it is computed, but systematic variations in accretion rates with time primarily portray an apparent dependency of river migration rates on time: these variations largely reflect the temporal resolution and timespan of the modelled examples, highlighting an inherent issue affecting studies of river evolutions.

Abstract The Walcott Quarry was discovered in 1909 by the Smithsonian Institute's Charles Doolittle Walcott (1850–1927). The Cambrian Burgess Shale (505 Ma, Miaolingian) crops out in the quarry and the lagerstätte is the nexus of ongoing vigorous debate about fossil preservation (including taphonomy and diagenesis), taxonomy, classification, phylogeny, and the origin of phyla and baupläne. Smithsonian Institute's field crews collected from 1909–24, and the quarry was subsequently expanded by Harvard University (1930), the Canadian Geological Survey (1966–67), and the Royal Ontario Museum (1992–2000). Approximately 250 000 fossils, including soft-bodied forms, have been collected, making the Walcott Quarry with exposures of the Middle Cambrian Burgess Shale, a significant geoheritage site and an important representation of the Cambrian Explosion.

Abstract The Town Creek locale in Jackson, Mississippi exposes fossiliferous strata through stream erosion and provides evidence for stratal doming atop an extinct volcano. Charles Lyell (1797–1875) investigated the locale on his second visit to North America (1845–46) and concluded that Town Creek fossils were older than Vicksburg fossils, and that strata dipped westward from Jackson. In the 1850s, Mississippi's state geologist Eugene Hilgard (1833–1916) recognized the first volcanic doming evidence and correctly concluded that a ‘local upheaval’ had elevated the Jackson area. Subsequent research revealed an extinct volcano as Jackson Dome's source, explaining the strata dip and Lyell's observation that Jackson's Eocene fossils were older than Vicksburg fossils, later identified as Oligocene. The Jackson fossiliferous strata, known today as the Moodys Branch Formation, exquisitely preserves fossils that have contributed to numerous scientific investigations. The Town Creek locale was threatened in 2003 when a proposed flood control project would have inundated it. Scientists rallied for the preservation of the geologically and historically important Town Creek, and today it remains as a geoheritage site available to scientists and the public, with a state historical marker noting its geological importance. Long-term preservation of the locale is needed but not guaranteed.

Abstract The Milwaukee Formation, a sequence of Givetian (Middle Devonian) marine strata deposited in what is now southeastern Wisconsin, USA, was recognized as preserving an exceptionally diverse biota of invertebrates, placoderms, and plants, when local cement companies mined the rock for the manufacture of hydraulic cement from 1876 to 1911. It is now recognized as containing one of North America's most diverse biotas of its age coming from a single formation, having roughly 250 species, 100 families, 16 phyla, and four kingdoms. Intense collecting has revealed the rich biodiversity that prevailed during the Devonian Period in what is now the Milwaukee area. When the cement mines shut down, the quarries were filled and what was already regarded as a localized series of outcrops became even more restricted. Today the formation is known almost exclusively from limited exposures in Estabrook Park and the adjoining Lincoln Park, in Milwaukee County, in the area once occupied by the cement quarries. These outcrops (the type locality) are protected by a Milwaukee County Park Ordinance that prohibits removing materials from the parks, thus enabling the type locality to remain intact for educational and non-destructive research purposes, while largely unstudied museum collections remain available for ongoing research.