The influence of rock uplift rate on the formation and preservation of individual marine terraces during multiple sea-level stands

Luca C Malatesta,Emily I Carreño,Kimberly L Huppert,Noah J Finnegan

doi:10.1130/g49245.1

Abstract

AbstractMarine terraces are a cornerstone for the study of paleo sea level and crustal deformation. Commonly, individual erosive marine terraces are attributed to unique sea-level high stands based on the reasoning that marine platforms could only be significantly widened at the beginning of an interglacial. However, this logic implies that wave erosion is insignificant at other times. We postulate that the erosion potential at a given bedrock elevation datum is proportional to the total duration of sea-level occupation at that datum. The total duration of sea-level occupation depends strongly on rock uplift rate. Certain rock uplift rates may promote the generation and preservation of particular terraces while others prevent them. For example, at rock uplift of ~1.2 mm/yr, the Marine Isotope Stage (MIS) 5e (ca. 120 ka) high stand reoccupies the elevation of the MIS 6d–e mid-stand, favoring creation of a wider terrace than at higher or lower rock uplift rates. Thus, misidentification of terraces can occur if each terrace in a sequence is assumed to form uniquely at successive interglacial high stands and to reflect their relative elevations. Developing a graphical proxy for the entire erosion potential of sea-level history allows us to address creation and preservation biases at different rock uplift rates.

Highlights

Marine terraces are key landforms for the study of paleo sea level (e.g., Broecker et al, 1968; Chappell, 1974; Machida, 1975) and crustal deformation (e.g., Otuka, 1934; Ota and Yoshikawa, 1978; Lajoie, 1986; Armijo et al, 1996)
We failed to identify a geological process that would explain an abundance of uplift rates between 0.8 and 1.1 mm/yr or a lower representation around 0.6 mm/yr. We suggest that this bimodality in apparent rock uplift rates may arise from a propensity for rock uplift rates of ∼0.9–1.2 mm/yr to favor the creation and preservation of Marine Isotope Stage (MIS) 5e terraces
Marine terraces provide a direct means of constraining the magnitude and timing of past sea level and solid earth deformation

Summary

INTRODUCTION

Marine terraces are key landforms for the study of paleo sea level (e.g., Broecker et al, 1968; Chappell, 1974; Machida, 1975) and crustal deformation (e.g., Otuka, 1934; Ota and Yoshikawa, 1978; Lajoie, 1986; Armijo et al, 1996). 120 ka terrace on San Nicolas Island, in the Channel Islands of California, which resulted in a mismatch between the ages of carbonate deposition and platform erosion at a true rock uplift of ∼0.25–0.27 mm/yr (Muhs et al, 2012) This potential for age-platform mismatch can be tracked across a spectrum of uplift rates in Figure 3 by comparing the elevations of high stands and those of long sea-level occupation. A global compilation of presumed MIS 5e marine terrace ages and elevations (Pedoja et al, 2014) suggests that time-averaged rock uplift rates at convergent margins since MIS 5e cluster around a primary peak at 0.2–0.3 mm/yr and a secondary peak around 0.9 mm/yr (Fig. 4A) We calculated these uplift rates assuming a globally consistent MIS 5e sea level equivalent to that of the present. We expect a large platform carved by repeated long-term sea-level occupation and wave erosion at and below sea level as is observed in the bathymetry (Figs. 4D and 4E)

DISCUSSION

CONCLUSIONS