AgeGrid dataset: age, spreading rates and spreading asymmetry of the world's ocean crust

The EarthByte Group presents four open-access companion datasets (grids). Four companion digital models of the age, age uncertainty, spreading rates and spreading asymmetries of the world's ocean basins are presented as geographic and Mercator grids with 2 minute resolution. The datasets include data from all the major ocean basins as well as detailed reconstructions of back-arc basins.
The age, spreading rate and asymmetry at each grid node is determined by linear interpolation between adjacent seafloor isochrons in the direction of spreading. Ages for ocean floor between the oldest identified magnetic anomalies and continental crust are interpolated by geological estimates of the ages of passive continental margin segments. The age uncertainties for grid cells coinciding with marine magnetic anomaly identifications, observed or rotated to their conjugate ridge flanks, are based on the difference between gridded age and observed age. The uncertainties are also a function of the distance of a given grid cell to the nearest age observation, and the proximity to fracture zones or other age discontinuities.
Asymmetries in crustal accretion appear to be frequently related to asthenospheric flow from mantle plumes to spreading ridges, resulting in ridge jumps towards hotspots. EarthByte Group also uses a new age grid to compute global residual basement depth grids from the difference between observed oceanic basement depth and predicted depth using two alternative age-depth relationships. The new set of grids helps to investigate prominent negative depth anomalies, which may be alternatively related to subducted slab material descending in the mantle or to asthenospheric flow. A combination of digital grids and the associated relative and absolute plate motion model with seismic tomography and mantle convection model outputs represent a valuable set of tools to investigate geodynamic problems.
Grid data, images and supporting documentation is available from the EarthByte website.  Images are available in .JPEG and .PDF format. Grid datasets may be read using GPlates, an open source software application developed in partnership with the EarthByte Group. For further information please refer to the associated publication and the EarthByte website.

EarthByte 团队发布了四套开放获取的配套网格数据集。本次发布的四款配套数字模型分别对应全球洋盆的年龄、年龄不确定性、扩张速率与扩张不对称性，以分辨率为2角分的地理坐标系与墨卡托（Mercator）网格形式呈现。该数据集涵盖全球所有主要洋盆的数据，同时包含弧后盆地的精细重建结果。

每个网格节点处的洋底年龄、扩张速率与不对称性，均通过沿扩张方向对相邻海底等时线（seafloor isochrons）进行线性插值计算得到。对于最古老已识别磁异常与大陆地壳之间的洋底年龄，则通过被动大陆边缘（passive continental margin）段的年龄地质估算值进行插值。与海洋磁异常识别点重合、或经旋转至对应洋脊侧翼的网格单元，其年龄不确定性基于网格化年龄与实测年龄的差值计算。该不确定性同时取决于目标网格单元到最近年龄观测点的距离，以及其与断裂带或其他年龄不连续界面的临近程度。

地壳增生过程中的不对称性通常与地幔柱（mantle plumes）向洋中脊（spreading ridges）输送的软流圈流动（asthenospheric flow）相关，进而导致洋中脊向热点（hotspots）方向跃迁。EarthByte 团队还基于两套可选的年龄-深度关系模型，通过实测洋壳基底深度与预测深度的差值，利用新的年龄网格计算得到全球残余基底深度网格。这套全新的网格数据集可用于研究显著的负深度异常，此类异常可能与地幔中俯冲板片（subducted slab）的下沉过程或软流圈流动相关。数字化网格、配套的相对与绝对板块运动模型，结合地震层析成像（seismic tomography）与地幔对流（mantle convection）模型的输出结果，构成了一套可用于地球动力学（geodynamic）问题研究的宝贵工具集。

网格数据、图像及配套文档可从 EarthByte 官网获取。图像格式支持 .JPEG 与 .PDF。网格数据集可通过 GPlates 读取，该软件是与 EarthByte 团队联合开发的开源应用程序。如需更多信息，请参考相关学术论文及 EarthByte 官网。