Lecture 4: Sedimentary Structures Produced by Sediment Transport

MIT RES.12-003 Fluid Motions, Sediment Transport, and Current-Generated Sedimentary Structures, Fall 2025 Instructor: John Southard View the complete course: https://ocw.mit.edu/courses/res-12-003-fluid-motions-sediment-transport-and-current-generated-sedimentary-structures-fall-2025/ YouTube Playlist: https://www.youtube.com/playlist?list=PLUl4u3cNGP60q1Ib4pyz_FBs_lYUPr9MN A detailed exploration of cross‑stratification reveals how sedimentary structures record the history of flowing water and waves. The video explains how bedforms such as ripples and dunes migrate and deposit layers that are later preserved as inclined laminae separated by erosion surfaces, allowing geologists to interpret past flow directions and conditions. It highlights different styles of cross‑stratification—such as climbing ripples, trough structures, and large dune deposits—and shows how their geometry depends on the balance between sediment supply and bedform movement. The discussion also extends to oscillatory and combined flows, introducing complex features like hummocky cross‑stratification and emphasizing the challenges of distinguishing between flow types in the rock record. Overall, the presentation demonstrates how careful observation of sedimentary patterns can be used to reconstruct ancient environments and flow dynamics. License: Creative Commons BY-NC-SA More information at https://ocw.mit.edu/terms More courses at https://ocw.mit.edu Support OCW at http://ow.ly/a1If50zVRlQ We encourage constructive comments and discussion on OCW’s YouTube and other social media channels. Personal attacks, hate speech, trolling, and inappropriate comments are not allowed and may be removed. More details at https://ocw.mit.edu/comments.