Misunderstanding Among the Geologist to Identify Global Stratigraphic Section and Point (GSSP) Boundary


Permian Triassic Boundary (PTB) is the most important transitional succession in Geological events. The great mass extinction events, called the Permian Mass extinction happened in this boundary, 251.94 Million years ago. The most devastation past event in which more 90% of marine species and 70% of terrestrial vertebrate families died out (Erwin, 1994). These great dying events occurred across the Permian Triassic Boundary. The Permian Triassic Boundary is most important to correlate and establish the great dying event globally. Now, Meishan Section (GSSP), South China (Global Stratotype Point and Section) is used to correlate the other Permian Triassic Boundary to identify the exact event horizon globally.

Geologist collecting rocks
The GSSP is determined based on the First Appearance of the Datum of any specific fossilInternational Commission on Stratigraphy ICS allows other possibilities to be used to establish the GSSP, including; the Last Appearance Datum, A magnetic reversal, Or geochemical signal in a well-studied stratigraphic succession (Cowie, 1986; Romane et al., 1996). 

Problems of GSSP Concepts as a FAD to Identify the PTB;

To establish any New stratigraphic succession by correlating with the GSSP  (Global Stratotype Point and Section), There is some misunderstanding and misusing the concept of GSSP.

Some Geologist uses Lowest Observed Occurrence Point in the replacements of the FAD  (First Appearance of the Datum) to identify and correlate with the established GSSP. This concept is a misunderstanding from the geologist or scientist. The GSSP concept is the use of the Conodont Fossil named Hindadus Parvus and based on the First Appearance of this Fossil is determined as a Global Stratotype Point and Section) for the GSSP section like Meishan Section, South China. The first  Conodont Fossil, Hindadus Parvus has been found at 251.88 Ma at the Meishan Section.

Here are some other misunderstandings of using rightly of the GSSP concept which makes the geologist a wrong correlation of the PTB for a new Stratigraphic section.

1. LOOP (Lowest Observed Occurrence Point) of H. parvusis used to estimate the boundary location, where the arrival of H. parvusin secondary successions represents a delayed or earlier occurrence Misunderstanding of  FAD (First Appearance of Datum), the PTB is often incorrectly placed at the first occurrence of H.parvus in secondary sections (e.g., Nicoll et al., 2002; Yin et al., 2014; Xu et al., 2017 .
2. The boundary-defining fossil/s may not even be found in a studied succession (e.g., Newton et al., 2004; Son et al., 2007; Richoz et al., 2010)
3. The boundary may be identified based on lithostratigraphy (Heydari and Hassanzadeh, 2003; Son et al., 2007)
4. The boundary interval may represent a disconformity (Lehrmann et al., 2003; Payne et al., 2007).

Understanding the Misunderstanding of the GSSP Concept to use;

To explain the misunderstanding by the Geologist or scientist to identify the new PTB from a new stratigraphic section is as discussed below in the Time-Distance Model.

Suppose, A Specific fossil, a marker of the PTB, like Hindadus Parvus, is searching in the rock strata by a Geologist. In the Time-distance diagram, the First appearance of Hindadus Parvus is a red point  (See Fig.) and this fossil will spread out everywhere in all direction after a certain time traveled and can be found like at the point C, D, E and B after a time travel of 3, 5, 8 and 4 respectively as a Lowest Observed Occurrence Point (LOOP) So, here, Geologist should find the red point as a First appearance datum to correlate with GSSP. But this is somewhat very difficult to find out in a new succession and hence difficult to correlate with the GSSP. But what the solution?? 
Another, important things to know is that, in the evolution cycle, the species will be found again in the point E, D at time 8 and 11 respectively. Unfavorable Facies and unconformity also play a role to appear a second time as a Highest Observed Occurrence Point (HOOP)

LOOP and HOOP are very important to identify the PTB. Because some Geologist can treat LOOP as a FAD. So, this is completely misunderstanding.
Now, what the solution to overcome this misunderstanding?? Here, comes the Graphic Correlation Model
Time-distance diagram modified from Eicher (1968)

Graphic Correlation Model;

Graphic Correlation Model is a very simple model and widely used in the oil exploration expert, or other geologists. The model has two successions in X and Y-axis as a Hypothetical Reference Section and a Hypothetical Comparison Section. Using this model is very accurate to identify and establish a correlated section. Here, the Hypothetical Reference Section indicates the established GSSP section data and the Hypothetical Comparison Section include all the data from the new section to be compared. Then, we have to compare both the LOOP and HOOP data for both sections. Then we will get a Line of Correlation Curve (LOC). This line of correlation curve will be projected in the established GSSP section and we can get the exact PTB of a new stratigraphic section.

Graphic Correlation Model

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