Geometrical Trends within sequences of Pleistocene marine Terraces: selected examples from California, Peru, Chile and New- Zealand

Description

Elevations of the shoreline angles of marine terraces have long been used to infer Pleistocene sea levels and/or uplift rates. We attempt to use morphologic properties of sequences of marine terraces-terrace width and slope-in order to track if these constitute a pattern showing similar alternations at different sites and if this alternation is comparable to the signal from the sea level highstand succession –duration and sea level-for Middle-Late Pleistocene. To do so, we focus on sequences of marine terrace including more than 10 successive strandlines from San Clemente Island and Santa Cruz (both in California, USA). We generated and analyzed 30 topographic profiles in order to confirm the occurrence or lack of each terrace, and to characterize their width and slope. To complement the observation of tenuous trends, we used additional data from previous works at Point Reyes (California, USA), Altos de Talinay (central Chile), San Juan de Marcona (central Peru) and South Taranaki (Northern Island, New Zealand). These additional data strengthen the observations made at San Clemente and Santa Cruz and prove that the most prominent terrace observed is usually carved during the Marine Isotopic Stage 5 (MIS5). Moreover, some terraces appear better expressed than the others: those formed during MIS7, MIS9 plus one of those formed during MIS15, MIS17 or MIS19 highstands. The terraces formed during MIS11 are not preeminent, contrary to what expected from its long highstand duration.

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