THE HOLOCENE HIGH ENERGY INTERVAL—A CLASSIC “NEUMANNISM”

Those of us who knew Conrad Neumann were aware of his gift to see concepts hidden from view but, in fact, were in broad daylight. All that was needed was a simple, but imaginative phrase or term, coined by a gifted observer, to bring these concepts into full view. “Bioerosion”, “lithoherm” ‘stiffification”, “carbogarbage”, “reefs shot in their back ”, and “catch up, keep up, give up” come to mind. Another was the “Holocene high energy interval”. We called these “Neumannisms” since they became common in Conrad’s view of the world. But, they all rang true and have been widely used by many not knowing their origin.

The Holocene high energy interval was not about some newly discovered global climate event. This Neumannism explained how sedimentological systems responded to the deceleration of sea level rise as the Last Glacial Maximum receded into the past. Barrier islands, coral reefs, carbonate sediment production and transport, seagrass/algal mat stabilization, and eolianite deposition as well as many other depositional systems all responded to this late Holocene deceleration of sea level rise. This allowed physical processes to be more focused spatially. Back in early 1970’s this was a near clairvoyant observation. Now, we take it for granted. Conrad could clearly see across the rigid boundaries that separated carbonate sedimentologists from siliciclastic sedimentologists, sediment process types from sediment facies distribution types, geophysicists from stratigraphers, and catastrophists from uniformitarianists.

The focus will be on the early flooding of the Bahamian carbonate platform and how depositional systems responded to the Holocene high energy interval. During early platform flooding the seafloor experienced vigorous physical energy from waves, tidal currents, and storm generated currents. Sands were transported offbank burying marginal reefs. As water depth increased due to continued, but slow sea level rise, benthic energy level decreased allowing seagrasses and algal mats to stabilize the substrate. Carbonate mud was produced changing the nature of sediments being exported seaward. Altogether, minor changes in sea level can significantly alter the depositional processes and resulting product along carbonate platform margins.