Paleogene orbitally calibrated climate cycles

就像树木年轮可以用来计算过去的天文年，古代珊瑚生长年轮可以用来估计过去每年的天数一样，未受干扰的沉积岩层可能会记录地球和其他行星轨道结构的周期性变化。这些天文变化影响大气顶部接收的太阳光的量，透过气候系统(例如冰期)，最终影响沉积在例如深海中的沉淀物的数量和类型。这些天文参数的变化：地球的偏心率、倾角(倾角)和气候进动(自旋轴的摆动)，发生在数千到数十万年的时间尺度上。最近才通过国际大洋钻探计划获得了深海必要的地质记录，该计划在几英里深的海床下数百米处采集沉积物岩心。以前的工作已经利用了岩石记录中内置的“节拍器”产生的各种机会，特别是如果这些相同的沉积层包含例如地球磁场方向的额外信息，海底的磁性线条告诉我们例如北美和欧亚大陆漂移的速度有多快，最重要的是可以更准确地确定日期的气候指标，从而提供关于气候变化发生的速度以及地球系统对外加的强迫或扰动的反应的信息。这种研究基本上是从现在到过去进行的，最近才公布了非常好的记录，可以追溯到3400万年前的始新世/渐新世地质界线。我们的中期目标是将这些校准和高分辨率的气候记录延伸到恐龙灭绝的时代，大约6500万年前，也就是众所周知的新生代。为了实现这一目标，在已知鳄鱼生活在北极圈内的一段时间内，世界处于更温暖的温室状态，我们想要分析针头大小(有孔虫)大小的海洋化石的化学成分，以获得有关气候循环、世界海洋某些位置的温度以及冰川和地球两极周围，特别是南极洲周围被困为冰的水量的信息。通过分析碳酸盐化石贝壳中的碳原子，我们还调查了二氧化碳消费者和生产者的演变，众所周知，二氧化碳消费者和生产者对气候周期做出反应。为了将岩石记录的‘天文时钟’倒流到我们长期目标的三分之二左右，我们通过向海底钻探获得了新的样本，以便恢复以每千年约1至2厘米的速度沉积的未受干扰的沉积物。

Just as tree rings can be used to count astronomical years back into the past and ancient coral growth rings can be used to estimate the number of days per year in the past, layers of undisturbed sedimentary rocks can potentially record cyclical variations in the orbital configuration of Earth and other planets. These astronomical variations affect the amount of sunshine received at the top of the atmosphere, filtered through the climate system (e.g. ice ages), which finally influences the amount and type of sediment deposited in, e.g., the deep sea. Changes of these astronomical parameters: the Earth's eccentricity, obliquity (tilt), and climatic precession (wobble of the spin axis), occur on time scales of thousands to hundreds of thousands of years. The necessary geological records from the deep sea have only recently become available through the international Ocean Drilling Program, which recovers sediment cores from hundreds of metres below the sea bed in waters several miles deep. Previous work has already exploited the various opportunities that arise from having a built-in 'metronome' in the rock record, and particularly if these same sediment layers contain additional information about, for example, the direction of the Earth's magnetic field, magnetic lineations on the sea-floor that tell us how quickly, for example, North America and Eurasia are drifting apart, and most importantly, climate indicators that can be more accurately dated, and thus give information on how fast climatic change can occur, and with what response of the Earth system to an applied forcing or perturbation. Such research has essentially been proceeded from the present into the past, and very good records were just recently published back to the Eocene/Oligocene geological boundary ca. 34 million years ago. Our medium term aim is to extend these calibrations and climate records at high resolution back to the age when the dinosaurs went extinct, ca. 65 million years ago, also known as the Cenozoic. To achieve this goal, for a time period when crocodiles were known to live within the Arctic circle, and the world was in a warmer, 'green-house' state, we want to analyse the chemical composition of fossilised marine fossils the size of a pin-head ('foraminifera') to gain information about climate cycles, the temperature at certain locations in the world's oceans, and the amount of water that was trapped as ice in glaciers and around the Earth's poles, particularly Antarctica. By analysing carbon atoms in carbonate fossil shells, we also investigate the evolution of carbon dioxide consumers and producers, which have been known to respond to climate cycles. To extend the 'astronomical clock' of the rock record back in time, to around two thirds of our longer term goal, we have obtained new samples through drilling into the sea-floor, in order to recover undisturbed sediments that are deposited at a rate of around 1 to 2 cm per thousand years.