美国地质调查局伍兹霍尔海岸和海洋科学中心Marcie Purkey Phillips团队近日揭示了自更新世以来波多黎各海沟内壁的千米级下沉。2025年5月29日，《地质学》杂志发表了这一成果。

研究组在波多黎各西北部的海山Mona Block的南侧观察到一层薄薄的更新世碳酸盐岩，水深1800米。Mona Block位于波多黎各海沟内壁内。1976年，阿尔文号深潜器（DSV）在莫纳地块北侧3650-2900米深处潜水时，遇到了类似的碳酸盐岩（珊瑚和路面）。

他们还观察到该地块东侧2080米深处有一个残留的渐新世-上新世碳酸盐台地。将碳酸盐露头恢复到接近海平面意味着，Mona地块目前的最高点为海拔670米，在更新世中期之前是一个海拔≥1000米的岛屿，此后已经下沉并向北倾斜。

研究组认为，观测到的沉降是由北美板块的沉没或退缩引起的，这导致了波多黎各海沟异常深。他们估计的沟槽壁沉降从远端约800m到沟槽附近≥3700m呈非线性变化。波多黎各北部的碳酸盐台地沉降更为古老（上新世中期），这表明沉降以及由此推断的海沟坍塌随着时间的推移向西传播。因此，蒙纳地块是研究与板块后退和沉没相关的地幔过程的标尺。

附：英文原文

Title: Kilometers-scale subsidence of the inner Puerto Rico Trench wall since the Pleistocene

Author: Uri ten Brink, Claudia Flores, Jason Chaytor, Marcie Purkey Phillips

Issue&Volume: 2025-05-29

Abstract: We have observed a thin veneer of Pleistocene-age carbonate rocks on the southern side of Mona Block, a seamount northwest of Puerto Rico, above a water depth of 1800 m. Mona Block is located within the inner wall of the Puerto Rico Trench. A similar veneer of carbonate rocks (corals and pavement) was encountered during a deep submergence vehicle (DSV) Alvin dive in 1976 on the north side of Mona Block at depths of 36502900 m. We also observed a remnant OligocenePliocene carbonate platform at a depth of 2080 m on the east side of the block. Restoring the carbonate outcrops to near sea level implies that Mona Block, with a summit currently at 670 m bsl, was an island with an elevation of ≥1000 m until the mid-Pleistocene and has subsided and tilted to the north thereafter. We suggest that the observed subsidence was caused by the foundering or retreating North American slab, which gave rise to the anomalously deep Puerto Rico Trench. Our estimated trench wall subsidence varies nonlinearly from ～800 m in the distal part to ≥3700 m near the trench. Carbonate platform subsidence north of Puerto Rico is older (mid-Pliocene), suggesting that subsidence and, by inference, trench collapse had propagated westward with time. Mona Block is thus a yardstick for studying mantle processes associated with slab retreat and foundering.

DOI: 10.1130/G53315.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G53315.1/654866/Kilometers-scale-subsidence-of-the-inner-Puerto