The Joint History of Tróia Peninsula and Sado Ebb-Delta

Abstract

Traditionally, the study of coastal evolution has focused on emergent barriers or stratigraphic sequences on the adjacent shelf, but seldom are these two systems studied holistically or the information combined into a single model. Here, we combine data sets from the emerged and submerged sectors of a prograding coast, from the coastal dune to the innermost continental shelf, to reconstruct the long-term history of shelf reworking and spit elongation of Tr oia Peninsula in Portugal. This analysis involves synthesizing high-resolution reflection seismic profiles from the shoreface, Ground Penetrating Radar images from the emerged sand barrier, high resolution digital terrain models, and Optically Stimulated Luminescence and radiocarbon dating of sediment samples from the emergent sand barrier and backbarrier. The results document the growth of the sandy peninsula in five major phases of progradation represented by massive foredunes separated by hiatuses of sedimentation and periods of shoreline stability. Formation of the peninsula began circa 6,500 years ago by spit elongation from the south as documented by the oldest beach sediments within the spit. The spit enlarged until a tidal inlet was formed around 3,300 years ago, which caused the construction of the ebb-tidal delta. The latter sequestrated the sand supplied to the spit inhibiting spit progradation until the ebb delta reached an equilibrium volume, allowing shoreline

Distribution patterns of microplastics in subtidal sediments from the Sado river estuary and the Arrábida marine park, Portugal

“…Likewise, MPs at stations 3-6, may be under permanent resuspension into the water column, which consequently decrease their availability on the seabed (Näkki et al, 2019;Shamskhany et al, 2021). An additional explanation is that, eventually, MPs might get buried at the submerged ebb-tide delta (Costas et al, 2015) located at the estuary mouth south margin, preventing the exportation of higher MPs abundances to the Arrábida coast. However, as sampling in this study was only conducted at the north margin, further studies would be necessary to clarify this possibility.…”

The role of climate, marine influence and sedimentation rates in late-Holocene estuarine evolution (SW Portugal)

“…BP (Costas et al, 2016b, and references therein). Costas et al (2015) mentioned an episode of shoreline retreat at the Tróia spit ca. 4000 cal.…”

“…Rodríguez-Ramírez et al, 2015) and along the Portuguese coast (e.g. Costas et al, 2015).…”

“…Ground Penetrating Radar and OSL dating at Tróia spit documented the growth history of the Peninsula in the last 6500 years (Costas et al, 2015). The northwards elongation of the Tróia spit from this date onwards reduced water exchange between the sea and the river and promoted the onset of low-energy conditions allowing sediment deposition within the estuary (Costas et al, 2015) and favouring the aggradation of the alluvial plain. The estuary has a Mediterranean flow regime with discharge of ca.…”

Simplified Marsh Response Model (SMRM): A Methodological Approach to Quantify the Evolution of Salt Marshes in a Sea-Level Rise Context

“…Sado estuary is separated from the Atlantic Ocean by Tróia sandspit, a 25 km-long barrier trending NNW-SSE. Five growing phases were identified in Tróia sandspit, dated from 6500 years to present (Figure 1C) [41]. Two test areas featuring salt marshes were selected on the estuarine margin of this spit (Figure 1C-E) to apply the SMRM and the SLAMM.…”