. Bulletins of American paleontology. 170 160 150 140 130 120 110 Annual Rainfall (cm) NOAA Area 5 5-year running mean Park Core 23A Mg/Ca (mmol/mol) L. matagordensis 30 35 40 45 I I I I. 50 I—I—I—I—1—I—1—I 1—I—1—I 170 160 150 140 130 120 110 Annual Rainfall (cm) NOAA Area 5 5-year running mean Bob Allen Core 6A Mg/Ca (mmol/mol) P. setipunctata 5 10 15 20 25 30 2000 .... 1 .... 1 .... 1 .... 1 .... 1 1990- 1980- o-^--fiS^^ 1970- 0^=^^^ 1960- 1950- 1940- ^^ 1930- ^^^ 1920- ^^^ 1910- ^^"^ 1900- ^^ 1890- tr*"^ 1880- 1870- 1 > 1860- ^^' 1850- ©=^, IftdO % . , . 1 . , . 1 . 1 . 1 170 1
. Bulletins of American paleontology. 170 160 150 140 130 120 110 Annual Rainfall (cm) NOAA Area 5 5-year running mean Park Core 23A Mg/Ca (mmol/mol) L. matagordensis 30 35 40 45 I I I I. 50 I—I—I—I—1—I—1—I 1—I—1—I 170 160 150 140 130 120 110 Annual Rainfall (cm) NOAA Area 5 5-year running mean Bob Allen Core 6A Mg/Ca (mmol/mol) P. setipunctata 5 10 15 20 25 30 2000 .... 1 .... 1 .... 1 .... 1 .... 1 1990- 1980- o-^--fiS^^ 1970- 0^=^^^ 1960- 1950- 1940- ^^ 1930- ^^^ 1920- ^^^ 1910- ^^"^ 1900- ^^ 1890- tr*"^ 1880- 1870- 1 > 1860- ^^' 1850- ©=^, IftdO % . , . 1 . , . 1 . 1 . 1 170 160 150 140 130 120 110 Annual Rainfall (cm) NOAA Area 5 5-year running mean Text-figure 8.—Ostracode Mg/Ca ratios versus age from RusselL Park, and Bob Allen Keys sediment cores plotted along with 5-year running mean of annual rainfall. Solid bars along left axis mark years of strong El Nino events. with salinity compared to that of Mg/Ca (Text-fig. 5). As a result of these potential temperature and water chemistry effects on Sr/Ca ratios, ostracode Mg/Ca ra- tios may be a more a sensitive indicator of salinity changes in Florida Bay. This contention is generally supported by the higher dynamic range displayed by the down-core Mg/Ca records and the apparent corre- lation between shell Mg/Ca ratios and rainfall (below). Comparison of Mg/Ca and Historical Rainfall To investigate whether the ostracode Mg/Ca ratios might be related to salinity variability, we compared downcore trends to historical rainfall records. We fo- cus our discussion on the records from Russell, Bob Allen, and Park cores as they have the most robust chronostratigraphy. Text-figure 8 shows the down-core records of ostracode Mg/Ca ratios versus year. Because rainfall derived runoff from peninsular Florida is such an important factor controlling the salinity of Florida Bay, we also show an instrumental record of south Florida annual rainfall which is available back to 1895 (NOAA Data Arch
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