GLY 101 1st Edition Lecture 13Outline of Last Lecture I. Numerical and Relative DatesA. Basic Principles of Relative DatingII. Inclusions and UnconformitiesOutline of Current Lecture III. FossilsIV. Correlation of Rock LayersV. Dating with RadioactivityCurrent LectureIII. Fossils-Paleontology- scientific study of fossilsTypes of Fossils1. permineralization- when mineral-rich groundwater permeates porous tissue, boneor wood, minerals precipitate out of solution and fill pores and empty spaces.2. molds and casts- a mold is created when a shell or other structure is buried in sediment and dissolved by underground water.- a mold only reflects the shape or surface of an organism, not the internal structure.- if the hollow spaces are filled with mineral matter, a cast is the result.3. carbonization and impressionsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- carbonization is exceptional at preserving leaves and delicate animal forms.-carbonization occurs when fine sediment encases the remains of an organism, as time passes, the liquid and gaseous components are squeezed out due to pressure and leaves behind a thin residue of carbon.- if the film of carbon is lost from a fossil preserved in fine grained sediment, a replica of the surface, called an impression, may still show detail. 4. Amber- amber is the hardened resin of ancient trees.- preserves delicate organisms, insects, and protects them from being damaged by water and air or crushed by pressure.5. Trace fossilsa. tracksb.burrowsc. coprolitesd. gastrolithsIV. Correlation of Rock Layers-the 1700s and 1800s is when fossils were seen as geologic tools.-Willian Smith discovered that each rock formation contained fossils different from the one above or below it.- He also noted that sedimentary strata in widely separated areas could be identified and correlated by their fossil content.- The Principle of Fossil Succession: Fossil organisms succeed one another in a definite and determinable order, and therefore any time period can e recognized by its fossil content.- index fossils provides geologists with a method of matching rocks of the same age. If index fossils are not present, fossil assemblage is used to establish the age of the bed.V. Dating with Radioactivity- in radioactivity the nuclei spontaneously break apart or decay.- common examples of radioactive decay1.alpha emission- composed of 2 protons and 2 neutrons2. beta emission- electron is given off from the nucleus3. electron capture- a electron combines with a proton and forms a neutron- the time required for half of the nuclei in a sample to decay is calledthe half-life of the isotope.-if the half-life of the radioactive isotope is known and the parent/daughter ratio can be determined, then age of the sample can be calculated.- carbon-14 is the radioactive isotope of carbon, the process is called radiocarbon