Investigation of micropaleontological and paleomagnetic data

Stephen A. Schellenberg
San Diego State University
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Micropaleontological and paleomagnetic data are investigated to construct an integrated biomagnetostratigrahic age model for an Ocean Drilling Program site. Investigation emphasizes the complementary nature of these two fundamentally different types of data and the primacy of age models in reconstructing Earth history.

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Upper-division majors to graduate level

Skills and concepts that students must have mastered

Fundamentals of biostratigraphy and magentostratigraphy; basic literacy in excel; familiarity with ocean drilling helpful but not critical.

How the activity is situated in the course

Stand-alone investigation with follow-up group discussion and comparison of results.


Content/concepts goals for this activity

Production and comparison of age models based on different microfossil and paleomagentic data from ocean drilling

Higher order thinking skills goals for this activity

Generate age models from discrete data; compare taxon-specific and "total evidence" age models

Other skills goals for this activity

Data management; Excel proficiency

Description of the activity/assignment

After exposure to the basic concepts of biostratigraphy and magnetostratigraphy, participants apply these concepts to produce a biomagnetostratigraphic age model using microfossil and paleomagnetic data from a Paleogene core recovered from Walvis Ridge in the South Atlantic (Ocean Drilling Program Site 1262). The investigation has three parts: First, observed first and last occurrences of various planktonic foraminifera species at different core depths are given absolute ages through reference to the Berggren et al. (1985) time-scale. Second, these planktonic foraminiferal data are used to identify magnetic reversals within the same core and thereby assign absolute ages to these events. Third, the resulting biomagnetostratigraphic age model is used to estimate the time between two well-documented "hyperthermals" within the core, the Paleocene-Eocene Thermal Maximum (PETM) and the Eocene Layer of Mysterious Origin (ELMO). The investigation illustrates how biostratigraphy and magnetostratigraphy complement one another and together provide an operational time-domain for all subsequent studies, be they paleoceanographic, evolutionary, etc. Note that this investigation operates on an established timescale (i.e., Berggren et al, 1985) and does not explictly demonstrate how such timescales are developed. Thus, instructors are encouraged to have students construct a simple composite relative time scale from basic outcrop data prior to this investigation.

Determining whether students have met the goals

Comparison and evaluation of resulting age models and answers to related questions.

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