Sceince of dating events using ice
"The source of the clay (laid down as shale) is from weathering of the land surface and the influx of clay to the seaway via rivers.The source of the calcium carbonate (limestone) is the shells of organisms, mostly microscopic, that lived in the water column." Meyers explains that while the link between climate change and sedimentation can be complex, the basic idea is simple: "Climate change influences the relative delivery of clay versus calcium carbonate, recording the astronomical signal in the process."Other studies have suggested the presence of chaos based on geologic data," says Meyers."But this is the first unambiguous evidence, made possible by the availability of high-quality, radioisotopic dates and the strong astronomical signal preserved in the rocks." In our solar system, an asteroid orbits the Sun in the opposite direction to the planets.In 1988, however, numerical calculations of the outer planets showed Pluto's orbit to be "chaotic" and the idea of a chaotic solar system was proposed in 1989 by astronomer Jacques Laskar, now at the Paris Observatory.Following Laskar's proposal of a chaotic solar system, scientists have been looking in earnest for definitive evidence that would support the idea, says Meyers.
It plays on the idea that small changes in the initial conditions of a nonlinear system can have large effects over time.
Where and how much solar radiation a planet gets is a key driver of climate.
"The impact of astronomical cycles on climate can be quite large," explains Meyers, noting as an example the pacing of Earth's ice ages, which have been reliably matched to periodic changes in the shape of Earth's orbit, and the tilt of our planet on its axis.
For example, imagine a very warm and wet climate state that pumps clay into the seaway via rivers, producing a clay-rich rock or shale, alternating with a drier and cooler climate state which pumps less clay into the seaway and produces a calcium carbonate-rich rock or limestone." The new study was supported by grants from the National Science Foundation.
It builds on a meticulous stratigraphic record and important astrochronologic studies of the Niobrara Formation, the latter conducted in the dissertation work of Robert Locklair, a former student of Sageman's at Northwestern.