Stable carbon and oxygen isotope rates of Maastrichtian ODP samples from Shatsky Rise

We present new isotopic and micropaleontological data from a depth transect on Shatsky Rise that record the response of the tropical Pacific to global biotic and oceanographic shifts during the mid-Maastrichtian. Results reveal a coupling between the upper ocean, characterized by a weak thermocline and low to intermediate productivity, and intermediate waters. During the earliest Maastrichtian, oxygen and neodymium isotope data suggest a significant contribution of relatively warm intermediate water from the North Pacific. Isotopic shifts through the early Maastrichtian suggest that this warmer water mass was gradually replaced by cooler waters originating in the Southern Ocean. Although the cooler water mass remained dominant through the remainder of the Maastrichtian, it was displaced intermittently at shallow intermediate depths by North Pacific intermediate water. The globally recognized "mid-Maastrichtian event" ~69 Ma, manifested by the brief appearance of abundant inoceramid bivalves over shallow portions of Shatsky Rise, is characterized by an abrupt increase (~2°-3°C) in sea surface temperatures, a greater flux of organic matter out of the surface ocean, and warmer (~4°C) intermediate waters. Results implicate simultaneous changes in surface waters and the sources/distribution patterns of intermediate water masses as an underlying cause for widespread biotic and oceanographic changes during mid-Maastrichtian time.

本研究报道了取自Shatsky海隆（Shatsky Rise）一条深度断面的全新同位素与微古生物学数据，这些数据记录了热带太平洋在马斯特里赫特期中期对全球生物与海洋学变化的响应。研究结果显示，以弱温跃层、低至中等初级生产力为特征的上层海洋与中层水之间存在耦合关系。在马斯特里赫特期早期，氧与钕同位素数据表明，北太平洋来源的相对温暖中层水占据了显著贡献份额。马斯特里赫特期早期的同位素偏移现象显示，这支暖水团逐渐被源自南大洋的冷水团所取代。尽管在马斯特里赫特期剩余时段内冷水团始终占据主导地位，但在浅中层深度处，它仍会间歇性地被北太平洋中层水所置换。全球公认的“马斯特里赫特期中期事件”（约69 Ma）以在Shatsky海隆浅水区短暂出现大量固着蛤双壳类（inoceramid bivalves）为典型表现，其特征为海表温度骤升约2℃-3℃、表层海洋有机质输出通量提升，以及中层水升温约4℃。本研究结果表明，表层海洋与中层水团的来源及分布格局同时发生变化，是马斯特里赫特期中期全球广泛出现生物与海洋学变化的核心诱因。