Research Summary:

This work demonstrates that low latitude surface seawater temperatures (SST) during the Middle Ordovician were similar to modern values. Oxygen isotopic values from marine cements were used as a proxy to constraint Ordovician SST's. This work is significant because the Middle Ordovician is a greenhouse period with elevated atmosphere pCO2 values in excess of 10 present atmospheric levels. Results support the premise that Phanerozoic low latitude SST's have remained constant around 25 to 30 C.

Funding Record:

Walker, K.R., and Tobin, K.J., Feb. 1994 to Jan. 1997, $154,960, Isotopic composition of early diagenetic carbonate from the Ordovician: implications for greenhouse paleoceanography and paleoclimate and pre-vascular plant meteoric diagenesis. National Science Foundation.

Papers:

Tobin, K.J., and Bergstrom, S. M., 2002, Implications of Ordovician (460 m.y.) marine cement for constraining seawater temperature and atmospheric pCO2, Palaeogeography, Palaeoclimatology, Palaeoecology. 181: 399-417.

Tobin, K.J., Steinhauff, D.M., and Walker, K.R., 1999, Ordovician meteoric carbon and oxygen values: implications for the latitudinal variations of ancient stable isotopic values, Palaeogeography, Palaeoclimatology, Palaeoecology. 150: 331-342.

Tobin, K.J., and Walker, K.R., 1997, Ordovician oxygen isotopes and paleotemperatures. Palaeogeography, Palaeoclimatology, Palaeoecology, 129: 269-290.

Abstracts:

Tobin, K.J., 2000, Implications of early Caradoc (460 m.y.) marine cement for constraining near-surface seawater temperature and atmospheric pCO2. GSA Abstract. 32(7), 299.

Tobin, K.J., 1999, Middle Caradocian (Ordovician) climate change on a greenhouse earth. GSA Abstract, 31(7): 417.

Tobin, K.J., and Walker, K.R., 1999, The MgCO3 contents of marine calcite: a record of Ordovician sea water chemistry and atmospheric CO2. EOS, Transactions. 80, S196.

Tobin, K.J., Steinhauff, D.M., and Walker, K.R., 1997, Ordovician meteoric carbon and oxygen values: is the present the key to the past. GSA Abstract, 29(7): 395.

Tobin, K.J. and Walker, K.R., 1995, Ordovician marine oxygen isotopes and low latitude seawater temperature, GSA Abstract, 27(7): 157.

Tobin, K.J., Walker, K.R., and Steinhauff, D.M., 1994, Least-altered, non-luminescent fibrous calcite from the Holston and Effna formations and Ordovician sea water temperature. GSA Abstract, 26(7): 131.