An Integrated Paleomagnetic, Isotopic, and Stratigraphic Test of the Inertial Interchange True Polar Wander Hypothesis, Bitter Springs Stage, Australia

自20世纪50年代以来，惯性交换真极移（IITPW）被认为是一个物理上可行的过程，在这个过程中，整个固体地球可能移动多达90。在106 - 107年之间。然而，IITPW事件在地质记录中没有得到令人信服的证明，主要有两个原因：（1）从不同大陆的各种岩石中收集的古磁极的年代、质量和相关性的不确定性一直困扰着研究;（2）没有认真努力将IITPW可能对地层记录的影响与全球气候结构、海洋环流、海平面、营养循环、有机碳埋藏、甲烷储存和大陆风化。IITPW假说提供了一系列可检验的预测，因为IITPW事件会对每个大陆产生不同的影响，但可以预测，这取决于大陆相对于地球自转轴的位置变化。例如，克拉通离惯性交流轴（Imin）越远，海平面和古地磁倾角的变化就越大。Maloofet等人[70]在东斯瓦尔巴特群岛（挪威）的8亿年（Ma）碳酸盐岩中发现了一个相对较轻的碳同位素区间，该区间被相对海平面和古地磁方向的大幅变化所包围。他们认为，这些同位素，磁性和地壳变化的巧合，可以解释与一对惯性交换真正的极地漂移IITPW事件相关的全球古地理的快速变化。在澳大利亚的苦泉组中也发现了相同的同位素间隔。澳大利亚是检验IITPW假说的理想地点，因为大多数新元古代中期古地理模型都将澳大利亚置于离伊敏更远的地方，而且与东斯瓦尔巴特群岛的方向不同。因此，thestratigraphy跨越这段时间在澳大利亚应显示独特的古地磁和海平面的变化，都是更大的幅度和不同的形状比那些记录在斯瓦尔巴特群岛。这一建议将测试IITPW假说，通过综合调查的物理，地球化学和磁性地层的苦泉阶段在澳大利亚。迄今为止所有的古地理重建都依赖于两个基本假设：（1）大陆的运动受板块构造的支配;（2）地球磁场在104年的时间尺度上是地心的和偶极的。此外，记录800年IITPW事件的沉积学和地球化学后果将有助于阐明至少三次新元古代冰川作用中的第一次之前的地球系统平衡。对IITPW假说的证伪将导致一系列同样重要的结果，这些结果记录了地磁场的古代长期变化或可能是意想不到的新元古代古地理。(1)大陆的分布对于理解地球上的流体循环至关重要。因此，从地质学和古地磁学角度研究真实的古地理学，对于建立古气候模型和理解全球变化的极限是必要的。(2)该提案将是PI领导的研究项目的开始，涉及与麻省理工学院（S.A.）的实验室合作。鲍林，B.P.韦斯），耶鲁大学（D.A.D.埃文斯）和加州理工学院（J.L. Kirschvink）。这些合作不仅将产生重要的科学成果，而且还将开始向普林斯顿大学进行技术转让，PI将于2006年在那里建立一个古地磁学实验室。(3)苦泉期的研究是一个理想的学生项目，因为它需要一套互补的学科知识，从基本的野外测绘和层序地层学到古地磁学，稳定和放射性同位素系统，以及整个地球物理学。PI将招募代表性不足的学生接受广泛的实地和分析方法培训，并在基于发现的研究科学中发挥积极作用。

Since the 1950s, inertial interchange true polar wander (IITPW) has been recognized as a phys-ically viable process in which the entire solid Earth may shift as much as 90. with respect to thespin axis in 106-107 years. Nevertheless, IITPW events have not been demonstrated convincinglyin the geologic record for two main reasons: (1) studies have been plagued by uncertainties inthe age, quality, and correlation of paleomagnetic poles collected from various types of rocks ondifferent continents, and (2) no serious effort has been made to link the effects IITPW may haveon the stratigraphic record due to changes in global climate structure, ocean circulation, sea level,nutrient cycling, organic carbon burial, methane storage, and continental weathering.The IITPW hypothesis provides a series of testable predictions because an IITPW event willaffect every continent differently, but predictably, depending on the continent's changing positionrelative to Earth's spin axis. For example, the further a craton is from the inertial interchangeaxis (Imin), the greater the changes in sea level and paleomagnetic inclination will be. Maloofet al. [70] identified an interval of relatively light carbon isotopes in *800 million year old (Ma)carbonate rocks of East Svalbard (Norway) that is bracketed by large shifts in relative sea leveland paleomagnetic orientation. They argue that the coincidence of these isotopic, magnetic, andeustatic changes can be explained by rapid shifts in global paleogeography associated with a pairof inertial interchange true polar wander IITPW events. The same isotopic interval has also beenidentified in Bitter Springs Formation equivalents in Australia. Australia is an ideal locality totest the IITPW hypothesis because most models of middle Neoproterozoic paleogeography placeAustralia further away and in a different direction from Imin than East Svalbard. Therefore, thestratigraphy spanning this interval in Australia should show unique paleomagnetic and sea levelshifts that are both larger in amplitude and different in shape than those documented in Svalbard.This proposal will test the IITPW hypothesis through an integrated investigation of the physical,geochemical, and magnetic stratigraphy of the Bitter Springs Stage in Australia.Intellectual Merit. All paleogeographic reconstructions to date rely on two fundamental as-sumptions: (1) the motion of continents is dominated by plate tectonics, and (2) Earth's magneticfield is geocentric and dipolar on time scales *104 yrs. Documenting IITPW in the geologic recordwould have profound implications for interpreting plate motions over the last 2 billion years. Fur-thermore, documenting the sedimentological and biogeochemical consequences of an IITPW eventat *800 would shed light on the equilibrium Earth System prior to the first of at least three majorNeoproterozoic glaciations. A falsification of the IITPW hypothesis would lead to an equally im-portant suite of results documenting ancient secular variation of the geomagnetic field or perhapsan unexpected Neoproterozoic paleogeography.Broader Impacts. (1) The distribution of continents is crucial to any first order understandingof general fluid circulation on the Earth. Therefore, the science of developing geologically andpaleomagnetically realistic paleogeographies is necessary for generating models of ancient climatesand for understanding the limits of global change. (2) This proposal will be the start of a researchproject led by the PI and involving laboratory collaborations with MIT (S.A. Bowring, B.P. Weiss),Yale (D.A.D. Evans), and Caltech (J.L. Kirschvink). These collaborations not only will produceimportant science, but also will begin a technology transfer to Princeton, where the PI will setup a paleomagnetics laboratory in 2006. (3) Study of the Bitter Springs Stage is an ideal studentproject because it requires the knowledge of a suite of complementary subjects, from basic fieldmapping and sequence stratigraphy to paleomagnetism, stable and radiogenic isotope systems, andwhole-Earth geophysics. The PI will recruit underrepresented students to receive extensive trainingin field and analytical methods, and to play active roles in discovery-based research science.