1. Conodont Biostratigraphy of the
Ordovician-Silurian Systemic Boundary Interval,
Nopah Range, Eastern California

2. W. Britt Leatham, CSU San Bernardino Amanda Wilcox, CSU San Bernardino
John D. Cooper, CSU Fullerton
Maziar Ahvari, CSU Fullerton

3. NV CA
NOPAH RANGE

5. Lithostratigraphic units
Sequences
Systems m
450
Lost Burro
KASKASKIA
Devonian
400
Sequence 5
Hidden Valley
350
Sequence 4
TIPPECANOE
Silurian
300
Sequence 3
Tony Grove Lake
250
200
150
Sequence 2
Ely Springs
Ordovician
100 50
Sequence 1
Eureka
SAUK

6. 180
160
Silurian
140
Ordovician
120
100 80 60 40 20

7. N 1
0.5 mi 2

8. W E S ? S  ? o Kaskaskia Sequence 5 Sequence 4 Sequence 3 Sequence 2
LB lss
Kaskaskia
u HV
Sequence 5 4
HVD
Sequence 4 4
l HV 3  S ?
chert 3 S
Sequence 3 ? o
ESD 2
Sequence 2 2 1
Sequence 1 1 EQ
SAUK
Traverse 1
Traverse 2

9. Ordovician-Silurian Boundary Interval
Sequence 3
Ordovician-Silurian Boundary Interval
350
Sequence boundary
300
SEQUENCE 3
Brecciated chert in bioclastic dolograinstones assigned to the “Hidden Valley”.
250
Bioclastic high-energy dolostones interbedded with microbial laminites. Bioclasts include Verticellipora, brachiopoda, tabulata, rugosa, and pelmatozoa
200
Feet above base
150
Peritidal to shallow subtidal, mottled dolostones and cryptalgally laminated dolomudstones to dolograinstones
100 50
Sequence boundary
Tan dolosilt-filled vugs with smooth floors and
irregular ceilings in bioturbated? N5 dolomudstone.

11. Ordovician-Silurian Boundary Interval
Sequence 3
Ordovician-Silurian Boundary Interval
350
Sequence boundary
300
SEQUENCE 3
Brecciated chert in bioclastic dolograinstones assigned to the “Hidden Valley”.
250
Bioclastic high-energy dolostones interbedded with microbial laminites. Bioclasts include Verticellipora, brachiopoda, tabulata, rugosa, and pelmatozoa
200
Feet above base
150
Peritidal to shallow subtidal, mottled dolostones and cryptalgally laminated dolomudstones to dolograinstones
100 50
Sequence boundary
Tan dolosilt-filled vugs with smooth floors and
irregular ceilings in bioturbated? N5 dolomudstone.

12. Ordovician-Silurian Boundary Interval
Sequence 3
Ordovician-Silurian Boundary Interval
350
Sequence boundary
300
SEQUENCE 3
Abundant late Llandoverian-early Wenlockian conodont fauna
250
200
Early Llandoverian (Aeronian-Rhuddanian) conodont fauna
Feet above base
150
Silurian
Ordovician
100
Richmondian-Gamachian conodont fauna 50
Sequence boundary
Cincinnatian conodont fauna

13. Richmond-Gamachian Conodont Species, Sequence 3
Aphelognathus shatzeri
Aph. shoshonensis
Drepanoistodus suberectus
Gamachignathus ensifer
Plectodina florida
Pl. tenuis
Pristognathus rohneri
Pseudobelodina dispansa
Ps. inclinata
Ps. vulgaris ultima
Pseudoonetodus mitratus
Staufferella sp.
Walliserodus amplissimus

14. Early Llandovery Conodont Species, Sequence 3
Ozarkodina hassi
Oulodus? kentuckyensis
Distomodus kentuckyensis
Walliserodus obliquicostatus
Walliserodus curvatus
Kockellela? manitoulinensis?

15. Conclusions
A Late Llandoverian-Early Wenlockian karsting in the Hidden Valley Dolomite had greater lithostratigraphic effects than terminal Ordovician glacio-eustacy in the Nopah Range, CA.
Conodont faunas change abruptly from late Ordovician forms to a low diversity fauna of Early Silurian aspect.
Terminal Ordovician glacio-eustatic sea-level fall did not produce a lithostratigraphically recognizable unconformity in the Nopah Range.

16. Sample
Feet above base

17. Ozarkodina hassi
S element
Pa element
Pa element

18. Oulodus? kentuckyensis
S element
Pa element
Distomodus kentuckyensis
Pa element

21. Shingle Pass--Ibex Graphic Correlation
Conodont Range Data

22. Conodont Occurrence Table
Tippecanoe Sequence 3
Conodont Occurrence Table