Possible Short Answer Question 5: (15 points total) Make a case for whether huma
ID: 120771 • Letter: P
Question
Possible Short Answer Question 5: (15 points total) Make a case for whether humans are geologic agents A) To define a new geologic time unit, there are strict criteria that must be met. Those criteria depend on whether the event is marked by a GSSP or a GSSA. Define what each acronym means, and outline the criteria for each. Make sure to explicitly note how the criteria differ Finally, provide an example of a geologic time unit boundary that is marked by a GSSP making sure to explicitly outline how the various criteria are met. (8 points)Explanation / Answer
The full form of GSSA is the Global Standard Stratigraphic Age. It is the chronological reference point in the geological record to define boundaries between different geological periods, ages, epochs in the overall geological time scale. The strata should be widespread and should contain an identifiable sequence of rock layers or other markers.
The full form of GSSP is Global Standard Stratotype Section and Point. It is the internationally agreed reference point on a stratigraphic section which define the lower boundary of the stage on the geological time scale. GSSPs are mainly based on the transitions between various faunal stages.
Criteria for GSSP:
The stratotype should include the name and rank of unit, locations of type and reference section including a map or air photo, detailed description of the stratrotype like character and height of the section, comments on the regional or local extent of unit, graphic log of the unit, location of curated reference material, discussion of unit's relationship with other contemporaneous units formed at the same time in adjacent areas.
The type section should be the best reference section available and should be well exposed
Both the top and bottom units should be visible.
The section should be complete and continuous as possible without faulting or long covered intervals.
The outcrop should be easily accesible and freely available for research purposes.
Comparison between GSSP and GSSA:
GSSA are used mainly for dating rocks older than 630 million years ago where good fossil record is lacking whereas GSSP is used for more recent periods and GSSP is based on paleontogical and improved methods of fossil dating. First the ICS( international commission on stratigraphy) first attempts to meet the standards of GSSPs. If these criteria fails then enough information is collected to define GSSA based on fixed dates and selected criteria.
The precambrian cambrian boundary at Fortune Head, Newfoundland is a typical example of GSSP. The site is easily accessible by paved road. The section is continuous in which clear boundary between precambrian and cambrian is visible. This boundary is set at the first appearance of a trace fossil Treptichnus Pedium which is found worldwide. The section is unlikely to washed away or builtover.
b. Golden Spikes are the preferred global markers of an event in the geological stratigraphic material eg rock, soil, sediments of glacier ice. For eg the appearance of new species as fossils within rocks with other changes like change in climate. The human golden spike were megafaunal extinction, origin of farming, industrial revolution, collision between old and new world, the great acceleration.
Out of these we chose megafaunal extinction as the human golden spikes. The megafaunal extinction took place between 50,000-10,000 years ago. Since other geological boundaries have been defined on the basis of faunal extintinction or other new emerging species so megafaunal extinction would be most suitable marker. Also during the megafaunal extinction half of all the large bodies mammals or total of 4% mammal species were lost The event occurred in almost all the continents eg Africa, Eurasia, North America, South America and Australia so the event is of global significance.