Author: Carolyn Gramling / Source: Science News
Early plants made Earth muddier. Ancient riverbed deposits of mud rock — rocks containing bits of clay and silt smaller than grains of sand — began increasing around 458 million years ago, around the time that rootless plants became common across Earth, researchers say.
Anecdotally, geologists have long noted that early sediment deposits became muddier at some point, and suggested a connection with plants (SN: 6/22/74, p. 398). But no one had ever pinpointed when that muddening happened.
So geologists William McMahon and Neil Davies, both of the University of Cambridge, decided to look for when amounts of mud rock began increasing in 704 ancient river deposits from 3.5 billion to 300 million years ago. The researchers searched through nearly 1,200 published papers for data on mud rock in river deposits, and collected new field data at 125 ancient river outcrops. At those outcrops, the researchers calculated the percent of mud rock in the overall deposit by measuring the thickness of the muddy layers compared with the thickness of layers containing larger grains such as sand.
The resulting fractions showed the median mud content was about 1 percent before around 458 million years ago.
At that point, the mud content steadily increased over about the next 100 million years or…The post Early land plants led to the rise of mud appeared first on FeedBox.