Thomas M. Cronin

The North American Genus Climacoidea Puri, 1956, and the Tribe Campylocytherini (Neogene and Quaternary)

The genera Reticulocythereis Puri, 1960, and Climacoidea Puri, 1956, which occur in Pliocene to Holocene marine deposits of the Atlantic and Gulf Coastal Plain, have been examined and found to possess a vertical row of four adductor muscle scars and two frontal scars, a carapace that is subovate in lateral view and widest behind the middle, and an amphidont hinge having a conical anterior tooth in the right valve. These and other characteristics indicate placement in the North American ostracode tribe Campylocytherini. Climacoidea and Reticulocythereis differ from one another and from the campylocytherine genus Proteoconcha Plusquellec and Sandberg, 1969, only in details of carapace ornament. We propose that Proteoconcha and Reticulocythereis be relegated to subgenera of the genus Climacoidea. As do other genera of the tribe, species of Climacoidea inhabit inner sublittoral to brackish environments in mild-temperate to subtropical waters. Two new species C. (Reticulocythereis) foresteri , and C. (Reticulocythereis) reticulata are diagnosed.

Mid-Pliocene deep-sea bottom water temperatures based on ostracode Mg/Ca ratios, supplement to: Cronin, Thomas M; Dowsett, Harry J; Dwyer, Gary S; Baker, Paul A; Chandler, Mark A (2005): Mid-Pliocene deep-sea bottom-water temperatures based on ostracode Mg/Ca ratios. Marine Micropaleontology, 54(3-4), 249-261

We studied magnesium:calcium (Mg/Ca) ratios in shells of the deep-sea ostracode genus Krithe from a short interval in the middle Pliocene between 3.29 and 2.97 Ma using deep-sea drilling sites in the North and South Atlantic in order to estimate bottom water temperatures (BWT) during a period of climatic warmth. Results from DSDP and ODP Sites 552A, 610A, 607, 658A, 659A, 661A and 704 for the period Ma reveal both depth and latitudinal gradients of mean Mg/Ca values. Shallower sites (552A, 610A and 607) have higher mean Mg/Ca ratios (10.3, 9.7, 10.1 mmol/mol) than deeper sites (661A, 6.3 mmol/mol), and high latitude North Atlantic sites (552A, 610 and 607) have higher Mg/Ca ratios than low latitude (658A: 9.8 mmol/mol, 659A: 7.7 mmol/mol, 661A: 6.3 mmol/mol) and Southern Ocean (704: 8.0 mmol/mol) sites. Converting Mg/Ca ratios into estimated temperatures using the calibration of Dwyer et al. (1995) [Dwyer, G.S., Cronin, T.M., Baker, P.A., Raymo, M.E., Buzas, J.S., Correge, T., 1995. North Atlantic deepwater temperature change during late Pliocene and late Quaternary climatic cycles. Science 270, 1347–1351] suggests that mean middle Pliocene bottom water temperatures at the study sites in the deep Atlantic were about the same as modern temperatures. However, brief pulses of elevated BWT occurred several times between 3.29 and 2.97 Ma in both the North and South Atlantic Ocean suggesting short-term changes in deep ocean circulation.