Submerged paleoshoreline mapping using high-resolution Chirp sub-bottom data, Northern Channel Islands platform, California, USA

Abstract

High-resolution Chirp sub-bottom data were obtained offshore from the Northern Channel Islands (NCI), California, to image submerged paleoshorelines and assess local uplift rates. Although modern bathymetry is often used for modeling paleoshorelines, Chirp data image paleoshorelines buried beneath sediment that obscures their seafloor expression. The NCI were a unified landmass during the last glacial maximum (LGM; ~20 ka), when eustatic sea level was ~120 m lower than present. We identified seven paleoshorelines, ranging from ~28 to 104 m in depth, across this now-submerged LGM platform. Paleoshoreline depths were compared to local sea-level curves to estimate ages, which suggest that some were reoccupied over multiple sea-level cycles. Additionally, previous studies determined conflicting uplift rates for the NCI, ranging from 0.16 to 1.5 m/ka. Our results suggest that a rate on the lower end of this range better fits the observed submerged paleoshorelines. Using the uplift rate of ~0.16 m/ka, we estimate that paleoshorelines formed during Marine Oxygen Isotope Stage 3, the LGM, and the Younger Dryas stade are preserved on the NCI platform. These results help clarify uplift rates for the NCI and illustrate the importance of sub-bottom data for mapping submerged paleoshorelines.

Zastosowanie atrybutów sejsmicznych odbić o wysokiej rozdzielczości do badania struktur 3D płytkiej geologii morskiej

“…The reflection signals reveal boundaries of sedimentary matters as mud, sand dunes, clay mixtures, Holocene structures, seabed, river channel sedimentation processes or even seagrass meadow distribution (Ianniruberto et al, 2012, Bui Viet et al, 2013, Le et al, 2020, Laws et al, 2019, Monnier et al, 2021. For improving the reflection seismic interpretation, computation of seismic attributes can be used for revealing many valuable structures or features hidden in abundant information raw seismic data.…”

Modeling and monitoring submerged prehistoric sites during offshore sand dredging and implications for the study of Early Holocene Coastal Occupation of Southern California

“…Despite the early discovery of archaeological materials and improved understanding of submerged paleolandscapes (Braje et al, 2019; Laws et al, 2020), there has been relatively little progress in underwater prehistoric site documentation off Southern California in the past few decades. At the same time, the existing coastline is increasingly threatened by reinvigorated sea‐level rise related to climate change (Reeder et al, 2012) as well as a scarcity of terrestrial sand input due to damming of local rivers (Brownlie & Taylor, 1981).…”

Sound Velocity in a Thin Shallowly Submerged Terrestrial-Marine Quaternary Succession (Northern Adriatic Sea)

“…Therefore, the shallow-most near-shore parts of presently submerged continental shelves extend over a considerable area globally and represent an important and often poorly studied geological environment. Due to the steadily increasing interest of the geological and archaeological research communities in shallow, presently submerged, and often buried landscapes [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41], accurate depth conversion is crucial for future geological studies and paleoenvironmental reconstructions in such settings. We investigate an example of a transgressed and submerged alluvial plain in the Bay of Koper (Gulf of Trieste, northern Adriatic Sea; Figure 1) to provide sound velocity values for thin (up to 20 m thick) Quaternary sediments deposited in terrestrial-marine sedimentary environments located in shallow near-shore environments a few tens of meters deep.…”