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

协作研究：坡道设置中序列几何和边界表面的控制

• 批准号: 9205811
• 负责人: Dag Nummedal
• 金额: $ 7.07万
• 依托单位: Louisiana State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1992
• 资助国家: 美国
• 起止时间: 1992-07-15 至 1994-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9205811&HistoricalAwards=false
• 关键词: COLLABORATIVE; RESEARCH; Controls; Sequence; Geometry

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.

输送到许多沉积盆地边缘的碎屑沉积物通常形成三角洲序列，这些序列在均匀加深的斜坡上前进和后退，而不是更常见的陆架-斜坡-盆底测深模型。 这种坡道设置中层序边界的属性以及层序元素（“系统域”）的几何形状和堆叠具有很大争议性，并且很少有已发表的示例得到很好的约束。 该项目是对坡道设置中序列几何的综合研究。 该项目将包括概念和数值建模，并在世界上暴露程度最好的碎屑斜坡序列之一：新墨西哥州圣胡安盆地的上白垩统边缘海洋沉积物中进行严格的现场测试。 该项目的主要目标是 (1) 识别、评估和绘制地层表面图，这些地层表面满足层序边界的客观标准，例如旧海洋地层的上重叠和地下暴露的向下移动，(2) 测试瞬时与层序边界的历时形成，（3）记录层序不同元素（系统域）之间沉积物的堆积模式和体积划分，（4）响应不同构造速率的层序几何形状的正演模型变化沉降、海平面变化的速率和幅度以及沉积物供应。 将应用二维弯曲背剥离来重建沉积表面随时间的几何形状。 建模将基于两种数值方法的组合。 一种是运动学模型，使用预设的沉积坡度和沉积物供应来生成对海平面和构造波动的地层响应。 第二个是模拟“前陆”盆地环境中沉积物输送的扩散模型。 该项目的总体目标是提高模型的精度，预测具有斜坡边缘的盆地中岩性单元的空间和时间分布，并能够从地层记录中提取有关过去海平面波动的更精确信息。