... Science Frontiers ONLINE No. 46: Jul-Aug 1986 Issue Contents Other pages Home Page Science Frontiers Online All Issues This Issue Sourcebook Project Sourcebook Subjects Which came first?The advent of complex life keeps getting pushed back farther and farther in time, as evidenced by the following abstract: "Microfossils resembling fecal pellets occur in acid-resistant residues and thin sections of Middle Cambrian in Early Proterozoic shale. The cylindrical microfossils average 50 x 110 microns and are the size and shape of fecal pellets produced by microscopic animals today. Pellets occur in dark gray and black rocks that were deposited in the facies that also preserves sulfide minerals and that represent environments analogous to those that preserve fecal pellets today. Rocks containing pellets and algal microfossils range in age from 0.53 to 1.9 gigayears ... Gyr) and include Burgess Shale, Greyson and Newland Formations, Rove Formation, and Gunflint Iron-Formation. Similar rock types of Archaean age, ranging from 2.68 to 3.8 Gyr, were barren of pellets. If the Proterozoic microfossils are fossilized fecal pellets, they provide evidence of metazoan life and a complex food chain at 1.9 Gyr ago. This occurrence predates macroscopic metazoan body fossils in the Ediacaran System at 0.67 Gyr, animal trace fossils from 0.9 to 1.3 Gyr, and fossils of unicellular eukaryotic plankton at 1.4 Gyr." (Robbins, Eleanora Iberall, et al; "Pellet Microfossils, Possible Evidence for Metazoan Life in Early Proterozoic Time," National Academy of Sciences, Proceedings, 82:5809, 1985 ...
Terms matched: 2 - Score: 147 - 15 May 2017 - URL: /sf046/sf046p14.htm
... debris drifting downwards from the ocean's upper layers. This is the "marine snow." Its constituents are mainly: ". .. the tiny leftovers of animals, plants, and non-living matter in the ocean's sun-suffused upper zones. Among these particles are chains of single-celled plants called diatoms, shreds of zooplankters' mucous food traps, soot, fecal pellets, dust motes, radioactive fallout, sand grains, pollen, and pollutants. Microorganisms also live inside and on top of these odd-shaped flakes." Marine snow is everywhere in the ocean. Sometimes, it reaches blizzard proportions, and divers cannot see beyond a few feet. Measured in millimeters, the marine snowflakes are much larger than the average interplanetary dust particles (but of ... interplanetary dust itself is also a constituent of marine snow). The bigger marine snowflakes -- over 0.5 mm -- are a major food source for deep-sea denizens waiting below for this manna from the watery heaven. The reason for mentioning marine snow in Science Frontiers is that biologists like Alldredge are really pio-neering new territory, where new anomalies must surely dwell. "' We've essentially discovered a whole new class of particles in the ocean that no one knew was there," she exults. .. .. . "' They're islands, really, where the metabolic activities of algae, bacteria, and protozoans produce unique chemical environments,' says Alldredge." To illustrate, the carbon content of bacteria on marine snow is 10, ...
Terms matched: 2 - Score: 26 - 15 May 2017 - URL: /sf093/sf093b05.htm
