The interplay between deformation, erosion and sedimentation in the deep-water Mexican Ridges foldbelt, western Gulf of Mexico basin

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• 作者：Ismael Yarbuh and Juan Contreras
• 刊名：Basin Research
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：29
• 期：S1
• 页码：446-464
• 全文大小：6487K
• ISSN：1365-2117

文摘

We analyse a regional 2D seismic section of the Mexican Ridges foldbelt (MRFB), western Gulf of Mexico, and construct excess-area diagrams for each of the structures comprising the foldbelt to estimate shortening, the onset of folding and the degradation of the folded seafloor. From the chronostratigraphy, we derive rates of tectonic and superficial mass transport and illustrate how they change across the MRFB. The resulting tectonic transport in the MRFB is 11.8 km forming a train of twelve buckle folds above a detachment at a depth of ca. 6 s of two-way travel time, with an average strain of ca. 10%. The fold train grew at a mean uplift rate of ca. 0.21 mm year⁻¹. Cross-sectional balancing demonstrates that shortening balances the down-slip motion of the Quetzalcoatl extensional system (QES), suggesting that horizontal compaction, volume loss and other penetrative deformation mechanisms are negligible. By assuming steady-state denudation, we are able to distinguish sediments derived locally from sediments transported from distant sources. The constant of mass diffusivity, a parameter controlling the degradation rate, is ca. 0.42 m² year ⁻¹, which is characteristic of rapid, episodic, superficial mass movements. The combined sedimentation rate from both, local and distal sources is ca. 0.23 mm year ⁻¹. Those values are not constant; structures proximal to the continental shelf are rising rapidly and are being degraded more intensely than those in the distal part of the MRFB, where sedimentation outweighs tectonic uplift. Our results indicate deformation initiated up to 3 Myr earlier than estimated from stacking patterns. Moreover, we find deformation started synchronously during the Late Miocene throughout the MRFB and not in two episodes as the stacking relations suggest. The discrepancy can be explained by a delay in the sedimentary response to folding. During early fold growth, nearly constant thickness strata are deposited before a progressive unconformity and other converging geometries develop. The development of growth strata is fast in the folds near the QES, which are being uplifted rapidly and degraded vigorously. Under these conditions, the stratigraphic relations give only a broad estimate of the pretectonic/syntectonic limit when compared to the excess-area method. On the other hand, the development of growth strata took twice as much time for folds near the abyssal plain, which are being uplifted at a slower rate and where degradation is less intense. Consequently, the delay takes more time, and the use of stratigraphic relations introduces an even more pronounced bias towards younger ages in the identification of the onset of folding.