GRAPHIC CORRELATION Assessing the Reliability of Stratigraphic Datums Integrating Data Sets and Assessing the Reliability of Stratigraphic Datums and the Completeness of Stratigraphic Sections Ron Martin Department of Geological Sciences University of Delaware Newark, DE 19716

DESCRIPTION OF THE EXERCISE ↓ DESCRIPTION OF THE EXERCISE 1) Students are sent an Excel file containing the depths of various types of datums from DSDP and ODP cores from different settings: ►biostratigraphic ►oxygen isotope ►paleomagnetic 2) Students then: ►plot datums ►evaluate the stratigraphic completeness of the cores based on the behavior of the datums. 3) After evaluating the plots, students answer questions about: ►reliability of datums ►stratigraphic completeness

↓ OBJECTIVES/GOALS 1) The objective of this exercise is to acquaint students with a simple graphic method that can be used to: ►Determine changes in sediment accumulation rate and ►Infer the reliability of various types of datums when correlating sections 2) By the end of the lab, students should understand how to: ►Make a simple plot of two different sections ►Infer what the plot tells one about changes in sediment accumulation rate and missing section (unconformities) ►Infer which datums in a particular section are most reliable for correlation ►Understand how non-traditional datums can be used to provide greater temporal (time) resolution between standard datums

HOW DO YOU “DO” GRAPHIC CORRELATION?

CORE LOCATIONS ☼ ☼

RESULTS!

QUESTIONS 1) Based on your plot, which core is most likely to be the most complete? Explain. 2) Does your answer to question 1 make sense in light of the depositional environments of the two cores? Why or why not? ☼ ☼

3) Would traditional biostratigraphic datums would you NOT trust 3) Would traditional biostratigraphic datums would you NOT trust? Explain.

4) Would the oxygen isotope data alone have been sufficient to infer any condensed sections or unconformities in these sections? Explain.

5) Which type of datums are indicating missing section?

5) What are the processes which might influence the quality of the fossil record, especially on the continental slope? --Turbidity currents --Slow, hemipelagic sedimentation (condensed sections) --Time-averaging of assemblages