Stacked fluvial and tide‐dominated estuarine deposits in high‐frequency (fourth‐order) sequences of the Eocene Central Basin, Spitsbergen

Abstract

Eighteen coastal-plain depositional sequences that can be correlated to shallow-to deep-water clinoforms in the Eocene Central Basin of Spitsbergen were studied in 1 · 15 km scale mountainside exposures. The overall mud-prone (>300 m thick) coastal-plain succession is divided by prominent fluvial erosion surfaces into vertically stacked depositional sequences, 7-44 m thick. The erosion surfaces are overlain by fluvial conglomerates and coarse-grained sandstones. The fluvial deposits show tidal influence at their seaward ends. The fluvial deposits pass upwards into macrotidal tide-dominated estuarine deposits, with coarse-grained riverdominated facies followed further seawards by high-and low-sinuosity tidal channels, upper-flow-regime tidal flats, and tidal sand bar facies associations. Laterally, marginal sandy to muddy tidal flat and marsh deposits occur. The fluvial/estuarine sequences are interpreted as having accumulated as a series of incised valley fills because: (i) the basal fluvial erosion surfaces, with at least 16 m of local erosional relief, are regional incisions; (ii) the basal fluvial deposits exhibit a significant basinward facies shift; (iii) the regional erosion surfaces can be correlated with rooted horizons in the interfluve areas; and (iv) the estuarine deposits onlap the valley walls in a landward direction. The coastal-plain deposits represent the topset to clinoforms that formed during progradational infilling of the Eocene Central Basin. Despite large-scale progradation, the sequences are volumetrically dominated by lowstand fluvial deposits and especially by transgressive estuarine deposits. The transgressive deposits are overlain by highstand units in only about 30% of the sequences. The depositional system remained an estuary even during highstand conditions, as evidenced by the continued bedload convergence in the inner-estuarine tidal channels.

Late Quaternary drainage dynamics in northern Brazil based on the study of a large paleochannel from southwestern Marajó Island

“…Although not diagnostic, the cross sets with abundant reactivation surfaces marked by mud drapes, which are particularly developed in the lower parts of the fining upward successions, lead to suggest possible sediment reworking by tidal currents, similarly to what has been recorded in many tidal channel successions (e.g., Boersma and Terwindt 1981, Mowbray and Visser 1984, Yang and Nio 1985, Leckie and Singh 1991, Shanley et al 1992, Hori et al 2001, Plink-Bjorklund 2005. In particular, the double mud drapes separating alternating thicker and thinner foreset packages their imprint in these sediments, which is probably due to the influence of strong fluvial inflow.…”

Márgenes costeros híbridos de la Cuenca Neuquina (Formación Allen, Cretácico Superior, Argentina).

“…In this paper, that tool made it possible to define facies associations with strong tidal influence. The deposits may have low preservation, and occur in drape forming rhythmites, or concentrated at the base of strata as intraclasts (Plink-Björklund, 2005;Yang et al, 2005). The presence of mud drape in the sedimentary record also contributes to infer periods of subaerial exposure of the plain because intense solar insolation and high temperatures promote the consolidation of muds during exposure and thus increases the potential for preservation (Anderson and Howell, 1984;Krogel and Fleming, 1998).…”

“…The sigmoidal sets in particular are generated by vortices in the flow separation area related to the acceleration and subsequent deceleration of the tidal flow. The alternating layers of sandstone and claystone reflect ebb and flow cycles in tidally dominated environments (Plink-Björklund, 2005). The sandy sets are deposited in the strong flow of the dominating current, while the mud layers correspond to the period of slack water where the flow velocity decreases and allows the deposition of suspended materials (Mellere and Steel, 1995).…”

Analisis estratigrafico secuencial de las formaciones Anacleto y Allen (Cretacico Tardio) en el borde nororiental de Cuenca Neuquina, Argentina

“…Los lotes sigmoidales, en particular, se generan por vórtices en la zona de separación de flujo relacionados con la aceleración y posterior desaceleración del flujo de la marea. La estratificación de bajo ángulo es el resultado del lavado de las ondas de arenas por acciones de retrabajo de las corrientes subordinadas (Plink-Björklund, 2005). En ambientes dominados por mareas la alternancia de láminas de areniscas y pelitas refleja los ciclos de 'flujo' y 'reflujo ' (Plink-Björklund, 2005).…”

“…La estratificación de bajo ángulo es el resultado del lavado de las ondas de arenas por acciones de retrabajo de las corrientes subordinadas (Plink-Björklund, 2005). En ambientes dominados por mareas la alternancia de láminas de areniscas y pelitas refleja los ciclos de 'flujo' y 'reflujo ' (Plink-Björklund, 2005). Los lotes arenosos se depositan durante el fuerte flujo de la corriente dominante, mientras que las capas pelíticas corresponden al período de agua calma en donde la velocidad del flujo disminuye y permite la depositación de materiales en suspensión (Mowbray y Visser, 1984;Mellere y Steel, 1995).…”