A Deep-Tow Magnetometer, SEABEAM, and Airgun Study of the Pacific Jurassic Quiet Zone

在过去三十年的地球科学研究中，冻结在海洋地壳中的磁反转模式的“录音机”类比是主要发现之一。虽然海洋磁力线的确定可以追溯到M38，但在太平洋，没有一个比M25更早的磁力线被证实是由磁场逆转引起的。评估这些最古老的异常的部分困难是由于它们具有典型的低振幅和明显的短周期。约翰逊和他的同事们建议建造一个磁力计，它将被拖到海底附近，与传统的船上或空中仪器相比，它更接近线的来源，它将探测到特别细微的特征。在22天的调查中，约翰逊和他的同事们还将分别收集海洋地壳和海底的地形测量数据，其中包括地震反射剖面和SEABEAM带状地图。将在西太平洋的三个地区进行调查，那里的m25后磁力线从以前的研究中已知。这些新数据将使建模研究能够比较三个研究领域的细节。如果发现波长和振幅的相似性，它们将有力地支持它们是磁场反转的真实记录的解释。如果未来的海洋钻探能够恢复并确定这些地层上沉积物的年代，那么海洋地磁逆转的时间尺度可能会再延长数百万年，回到侏罗纪。

The "tape recorder" analogy of magnetic reversal patterns frozen into oceanic crust has been one of the major discoveries in the last three decades of earth science research. Though marine magnetic lineations have been identified back to M38, none in the Pacific that are older than M25 have yet been proven conclusively to result from field reversals. Part of the difficulty in evaluating these oldest anomalies results from their characteristically low amplitudes and apparently short periods. Johnson and his colleagues propose to construct a magnetometer that will be towed near the seafloor, and being closer to the source of the lineations than conventional shipboard or airborne instruments, this device will detect especially subtle features. During 22 days of surveying, Johnson and his colleagues will also gather topographic measurements of the oceanic crust and the seafloor with seismic reflection profiles and SEABEAM swath maps, respectively. Three regions will be surveyed in the western Pacific where post-M25 magnetic lineations are known from previous studies. These new data will allow modelling studies to compare details among the three study areas. If similarities in wavelength and amplitude are found, they will strongly support the interpretation that they are true records of magnetic field reversals. If future ocean drilling recovers and dates the sediments resting on these lineations, the marine magnetic reversal time scale could be extended several millions of years further back into the Jurassic.