Giga-fren The dynamic nature of the floodplain topography is reflected in alternating drainage conditions, represented by quasi-regular colour banding, compound clay coatings, and the type and degree of pedogenic development upwards within the paleosol successions. Giga-fren However, the subsequent transition to pedogenic carbonates, eolian sands, and lower diversity floras is not matched by significant poleward latitudinal motion.

EurLex-2 The silty-clayey soil has a large quantity of total and active limestone as a result of the carbonate nature of the pedogenic sediments. EurLex-2 Domain of a soil with a certain vertical extension, more or less parallel to the surface and homogeneous for most morphological and analytical characteristics, developed in a parent material layer through pedogenic processes or made up of in-situ sedimented organic residues of up-growing plants peat.

EurLex-2 Last non-pedogenic process geologic or anthropogenic that coined the material composition and internal structure of the layer. Giga-fren Metamorphism and deformation also tend to mask pedogenic features, as attested by the scarcity of documented occurrences of medium- to high-grade metamorphosed Precambrian paleosols in Canada.

Geochemical distribution of the elements. Knowledge of the geochemical distribution of elements involves elucidation of the relative and absolute abundances of the chemical elements in the Earth and in its various parts—the crust, interior, atmosphere, and hydrosphere. This comprises a major part of the science of geochemistry, which is the study of the distribution of the chemical elements.

Algae Algae comprise several different groups of organisms which produce energy through photosynthesis and for that reason have been included in the plant kingdom in the past. Most conspicuous among the algae are the seaweeds , multicellular algae that may roughly resemble land plants, but are classified among the brown , red and green algae. Each of these algal groups also includes various microscopic and single-celled organisms.

There is good evidence that some of these algal groups arose independently from separate non-photosynthetic ancestors, with the result that the brown algae , for example, are no longer classified within the plant kingdom as it is defined here. With a few exceptions among green algae, the green plants have the following features in common; cell walls containing cellulose , chloroplasts containing chlorophylls a and b, and food stores in the form of starch contained within the plastids.

They undergo closed mitosis without centrioles , and typically have mitochondria with flat cristae. The chloroplasts of green plants are surrounded by two membranes, suggesting they originated directly from endosymbiotic cyanobacteria. Two additional groups, the Rhodophyta red algae and Glaucophyta glaucophyte algae , also have chloroplasts that appear to be derived directly from endosymbiotic cyanobacteria , although they differ in the pigments which are used in photosynthesis from those of the Viridiplantae and so are different in colour.

In these groups, the storage polysaccharide is floridean starch and is stored in the cytoplasm rather than in the plastids. These groups appear to have had a common origin with Viridiplantae and the three groups form the clade Archaeplastida , whose name implies that their chloroplasts were derived from a single ancient endosymbiotic event. This is the broadest modern definition of the term ‘plant’.