The Carbon Isotope Record of the Great Ordovician Biodiversification Event Carlos Y. Vélez

Content 1.Introduction 2.Location a)Site b)Sample 3.Methodology 4.XRD Graphs 5.Objectives 6.Goals 7.Questions

Introduction The Ordovician Period is from 505 to 440 Million Years Ago. It have three major divisions. Lots of diversification!

Characteristics of the Wah Wah Limestone Located in the J Section of Hintze Well exposed in the mountain front between section H and J 78.6 m thick, the lower 67.6 m is Ibexian and the upper is Whiterockian Medium grey to medium dark grey Extremely well bedded Fine grained limestone to coarse grained clastic limestone Silty limestone with flat pebble conglomerate Towards the top of the unit, beds become more resistant Fossils include gastropods, ostracods, and trilobite debris

Great Ordovician Biodiversification Turnover in graptolites, conodonts, and chitinozoans This produced a strong and positive  13 C excursion Major plate motions involving Laurentia, may have been primary forces to these biodiversity changes. (William B.N.) The record shows that no major extinctions preceded the Ordovician radiation New groups that appeared during the Ordovician dominated the next 250 MY. (M. L. Droser 1996)

Ordovician World

Site Location

Sample Location N S WE

N S WE

Antelope Valley in Ely, Nevada

Methodology 35 samples were collected from the Section J Juab Limestone. Additional 92 from Antelope Valley outcrops of the Goodwin Limestone. 1)Samples were crushed using a custom-made “steel crushing machine”. 2)Sieved using a 4” kitchen strainer. Fine-grained powders will be used for mass spectrometer and XRD analysis.

Take the sample in the field Methodology of the samples Back to PR  Get a fresh piece of the sample Crush the sample Sieve the sample UtahMy House For mi- neralogy analysis RUM Put the sample in the vial For isotope analysis Dry Weigh Put the vial in the mass spectrometer Put the holder in the XRD machine Put the sample in the sample holder

Results

Mole & weight percentages

Weight percent of Carbonate

Target in μgrams for 2.5 μmoles of CO 2

Research Objectives Correlation between the two sample localities. Relationship between the Middle Ordovician diversification event and carbon isotope variation. Speculate on the causes for the Middle Ordovician diversification event. Correlations will be made in the carbon isotope stratigraphy of two localities in the eastern Great Basin.

Great Ordovician Biodiversification begins in these two units. The carbon isotope changes may allow a very precise correlation between the two units. No one has ever studied this interval before. Why relationship between carbon isotope changes and biological evolution in the Juab and Goodwin Limestones?

Conclusions