Non uniform sediment deposition dating
Because higher discharge increases velocity and higher velocity increases erosion, there is often a strong correlation between these factors. Most of the sediment is produced by WEATHERING and moved into the channel by MASS WASTING. River and stream deposits are called alluvial deposits; .
a) Channel deposits - BARS occur on the inside of river bends (point bars) and in the channel itself (mid-channel bars - often formed in streams having large sediment loads and greatly fluctuating discharges, where they form BRAIDED STREAMS.
Once the organism dies the 14C/regular carbon ratio decreases.
b) Floodplains - formed by flood deposits in area adjacent to channel.OCCURRENCE OF IGNEOUS ROCKS: Batholiths, laccoliths, lava flows, sills, dykes, volcanic necks. This results in "rock cleavage" (not to be confused with mineral cleavage), which means the rock splits very easily along the foliation planes. It is interesting to note that although the earliest-known life is over 3.2 billion years old, there is very little fossil evidence for it.It is not until about 540 million years ago that fossils became abundant, probably due to the development of hard body parts (shells, skeletons). certain isotopes (Parent) spontaneously emit atomic particles (protons and neutrons) and in so doing change to a different element (Daughter).CLASSIFICATION OF IGNEOUS ROCKS: GRANITIC ROCKS - : intrusive = GABBRO, extrusive = BASALT. The heat and pressure "metamorphoses" rock usually by causing: ( mineral grains resulting from their adjustment to pressure, giving the rock a layered appearance. REGIONAL METAMORPHISM: large scale heat and pressure due to earth movements. PHYLLITE - LOW-INTERMEDIATE GRADE metamorphism of shale causes growth of larger, but still invisible, mica or chlorite crystals. SCHIST - INTERMEDIATE GRADE metamorphism of shale causes the growth of larger mica flakes, visible to the naked eye. Absolute dating was not available and so each interval was based mainly on fossils and reflected a major change in life forms.ULTRAMAFICS: intrusive = PERIDOTITE, extrusive = KOMATITE (very rare). (*note - a common property of metamorphic rocks is that they are often denser than the original rock, because they form under pressure). The compression of large segments of the Earth's crust occurs due to TECTONIC ACTIVITY (covered later in course). DYNAMIC METAMORPHISM: occurs along fault zones, where rocks are shattered, usually producing fault BRECCIAS. SLATE - clay minerals in SHALE are transformed into minute flakes of mica, which align themselves perpendicular to the direction of pressure, forming very fine, flat, parallel planes of foliation. The relative order of the divisions was based on superposition and correlation. Periods - each era is divided into a number of periods, based on life form changes.