COLLABORATIVE RESEARCH: Controls on Sequence Geometry and Bounding Surfaces in Ramp Settings

碎屑沉积物被运送到许多沉积物的边缘， 盆地通常形成三角洲序列， 在均匀加深的坡道上后退，而不是更常见的 模拟陆棚-斜坡-盆地底水深测量。 的性质 层序界面、层序的几何形态和叠置方式 在这样的斜坡设置中的元素（“系统域”）是高度 有争议的，很少有出版的例子是很好的限制。 本项目是一个综合性的研究序列几何在坡道 设置. 该项目将包括概念和数字 建模伴随着严格的现场测试， 世界碎屑岩斜坡序列的暴露序列： 圣胡安盆地晚白垩世边缘海相沉积， 新墨西哥州。 本项目的主要目标是（1） 确定、评价和绘制地层表面， 层序界面向下移动的客观标准 较老的海相地层的上超和陆上暴露，（2）测试 层序瞬时形成与历时形成的概念 边界，（3）文档堆叠模式和体积 沉积物在不同元素（系统）之间的分配 （4）层序的正演模式变化 几何学对不同的构造沉降率的反应， 海平面变化的速率和幅度以及沉积物供应。 二维弯曲回剥将应用于 通过时间重建沉积表面的几何形状。 建模将基于两个数值的组合 方法. 一种是使用预设沉积坡度的运动学模型 和沉积物供应，以产生地层对海洋的响应 水平和构造波动。 二是扩散模型 它模拟了“前陆”盆地环境中的沉积物迁移。 该项目的总体目标是提供更高的精度， 模型预测的空间和时间分布 岩性单位在盆地与斜坡边缘，并使 提取有关过去海平面的更精确信息 地层记录的波动

Clastic sediments delivered to the margins of many sedimentary basins commonly form deltaic successions which forestep and backstep on evenly deepening ramps, rather than the more commonly modeled shelf-slope-basin floor bathymetry. The properties of sequence boundaries, and the geometry and stacking of sequence elements ("systems tracts") in such ramp settings are highly controversial and very few published examples are well constrained. This project is an integrated study of sequence geometry in ramp settings. The project will consist of conceptual and numerical modeling accompanied by rigorous field testing in one of the best exposed successions of clastic ramp sequences in the world: the Upper Cretaceous marginal marine deposits of the San Juan basin, New Mexico. The primary objectives of this project are to (1) identify, evaluate and map stratigraphic surfaces, which meet such objective criteria for a sequence boundary as downward shift in onlap and subaerial exposure of older marine strata, (2) test the concepts of instantaneous versus diachronous formation of sequence boundaries, (3) document stacking patterns and volumetric partitioning of sediment between different elements (systems tracts) of the sequences, (4) forward model variations in sequence geometry in response to different rates of tectonic subsidence, rates and amplitudes of sea level change, and sediment supply. Two-dimensional, flexural backstripping will be applied to reconstruct the geometry of the depositional surfaces through time. The modeling will be based on a combination of two numerical methods. One is a kinematic model using preset depositional slopes and sediment supply to generate the stratigraphic response to sea level and tectonic fluctuations. The second is a diffusion model that simulates sediment transport in a "foreland" basin setting. The overall goal of the project is to provide improved precision in models predicting the spatial and temporal distribution of lithologic units in basins with ramp margins, and to enable the extraction of more precise information about past sea level fluctuations from the stratigraphic record.