Changes in the concentration and isotopic composition of the major constituents in seawater reflect changes in their sources and sinks. Because many of the processes controlling these sources and sinks are tied to the cycling of carbon, such records can provide insights into what drives past changes in atmospheric carbon dioxide and climate. Here, we present a stable strontium (Sr) isotope record derived from pelagic marine barite. Our δ^88/86Sr record exhibits a complex pattern, first declining between 35 and 15 million years ago (Ma), then increasing from 15 to 5 Ma, before declining again from ~5 Ma to the present. Numerical modeling reveals that the associated fluctuations in seawater Sr concentrations are about ±25% relative to present-day seawater. We interpret the δ^88/86Sr data as reflecting changes in the mineralogy and burial location of biogenic carbonates.

海水中主要成分的浓度和同位素组成的变化反映了其来源和汇的变化。由于控制这些源和汇的许多过程都与碳循环有关，因此此类记录可以提供洞察力，以了解过去二氧化碳和气候变化的驱动力。在这里，我们提出了来自上层海洋重晶石的稳定锶（Sr）同位素记录。我们的^δ88/86 Sr记录表现出复杂的模式，在35至1500万年前（Ma）之前下降，然后从15 Ma上升到5 Ma，然后再从^〜5 Ma下降到现在。数值模拟表明，海水中Sr浓度的相关波动相对于当今的海水约为±25％。我们解释^δ88/86Sr数据反映了生物碳酸盐的矿物学和埋藏位置的变化。