M.'s considered opinions

Usage examples of sediments.

The oldest eukaryotes yet known, called Grypania, were discovered in iron sediments in Michigan in 1992.

The first hint of how abundant life is in the deep seas didn’t come until as recently as the 1960s with the invention of the epibenthic sled, a dredging device that captures organisms not just on and near the seafloor but also buried in the sediments beneath.

Indeed, neither Stromer and Markgraf nor the 2000 expedition team ever found evidence of ornithopods, though they have been found in Early Cretaceous sediments in Niger.

A quiet environment for sediments to be deposited century after century.

He also knew that the sea level was rising, rather than falling, because there was no evidence in the el Dist sediments of an erosional environment, of rivers flowing downhill toward a receding seashore.

Then, at the moment of slack tide, you’d see finer silty sediments settling into the hollows between those ripples.

If the sediments remain undisturbed, eventually the record of each change in the tide in that channel is preserved for all time by rock, with little lenses of siltstone encased in the surrounding sandstone.

Normally, when sea levels rise, marine sediments will cover over beach and intertidal or lagoon areas, as the seafloor gradually migrates landward.

But it seemed to Lacovara that instead of being buried by marine sediments as the sea level rose, the intertidal sediments in what he and Jennifer Smith were calling the unconformable sequence were doing the opposite: actually advancing into the marine zone.

Since the sediments of Gebel el Dist have been undisturbed by major geological forces, they remain in their original horizontal position.

Not only do the sediments look the same, but often the fauna does, too.

If you multiplied the rate of deposition by the number of years it had been going on, it produced a disturbing figure: there should be about twelve miles of sediments on the ocean bottoms—or, put another way, the ocean bottoms should by now be well above the ocean tops.

If the ocean floors were ancient, as everyone assumed, they should be thickly blanketed with sediments, like the mud on the bottom of a river or lake.

In 2001 researchers at the California Institute of Technology analyzed helium isotopes from sediments left from the later KT impact and concluded that it affected Earth’s climate for about ten thousand years.

Then as the sediments in which the fossil lies are carelessly pressed and folded and pushed about by Earth’s processes, the fossil must somehow maintain an identifiable shape.