By: magic-gigapans
Image: ahochstaedter ⧉
License: Copyright, All Rights Reserved

Uploaded: 10 Jul 2020
Last Updated: 10 Jul 2020

694 megapixels
37,640 x 18,436 pixels
125.5 in X 61.5 in at 300dpi

Cretaceous turbidites crop out along the sea cliff at Garrapata Beach in Big Sur, CA. Turbidites are characterized by graded bedding with coarser clasts at the bottom and finer material at the top of the deposit. They are recognized here by the alternating sands and shales in the sea cliff. Turbidites are deposited by turbidity currents, density-driven flows that occur when sediment and water mix to create a fluid with a density higher than that of water. This high density slurry flows down slope and can keep moving over a long horizontal distance after it reaches the bottom of the slope. This processes produces submarine fans at the base of continental slopes; turbidity currents are one of the most important mechanisms for transporting sediment from the continent into the deep ocean. Idealized turbidite deposits have five layers distinguished by their sedimentary structures. These layers were first described by Bouma, and bear his name today. From bottom to top, the Bouma sequence consists of sands or larger grains, parallel laminated sands, cross laminated sands, parallel laminated silts, and muds. Seeing these various layers may be beyond the focus limits of this image, but they are easily visible on close-up images of these beds: The turbidite beds are overlain in angular unconformity by beach sands with a basal boulder layer, visible in the center right portion of the image. This angular unconformity formed while these rocks were being eroded on the wave-cut platform of a previous beach. As uplift continued, the rocks and the overlying sand and gravel beach sediments rose above sea level to form a marine terrace. Marine terraces are visible above the sea cliff left of center in the image. Close-up images of the turbidites are here: http://zoom.it/dKU6 http://zoom.it/4v4T