Allogenic and autogenic processes combined in the formation of shallow-water carbonate sequences (Middle Berriasian, Swiss and French Jura Mountains)

Abstract

Sediment production and accumulation on shallow carbonate platforms are controlled by allogenic, externally controlled processes (such as sea level, climate, and/or platform-wide subsidence patterns) as well as by autogenic factors that are inherent to the sedimentary system (such as lateral migration of sediment bodies). The challenge is to determine how and in which proportion these processes interacted to create the observed sedimentary record. Here, a case study of Middle Berriasian, shallowmarine carbonates of the Swiss and French Jura Mountains is presented. Based on vertical facies evolution and bedding surfaces, different orders of depositional sequences (elementary, small-scale, medium-scale) have been identified in the studied sections. The hierarchical stacking pattern of these sequences and the time span represented by the investigated interval imply that eustatic sea-level fluctuations in the Milankovitch frequency band were an important controlling factor. The small-scale and medium-scale sequences relate to the 100 and 400-kyr orbital eccentricity cycles, respectively. The elementary sequences are attributed to the 20-kyr precession cycle. Differential subsidence additionally produced accommodation changes. The present study focuses on one specific small-scale sequence situated at the base of the transgressive systems tract of large-scale sequence Be4, which is identified also in other European basins. This small-scale sequence has been logged in detail at eight different outcrops in the Jura Mountains. Detailed facies analysis reveals that different depositional environments (tidal flats, internal lagoons, open lagoons, carbonate sand shoals) were juxtaposed and evolved through time, often shifting position on the platform. The boundaries of the small-scale (100-kyr) sequence can be followed over the entire study area and thus must have formed through predominantly allogenic processes (eustatic sea-level fall, the effect of which was locally modified by differential subsidence). In two sections, five well-developed elementary sequences constitute the smallscale sequence. In the other sections, the identification of elementary sequences often is difficult because sedimentation was dominated by autogenic processes that overruled the influence of sea-level fluctuations. In low-energy, tidalflat and internal-lagoonal settings, orbitally induced sea-level changes were recorded more faithfully, while high-energy shoals were mainly submitted to autogenic processes and the allogenic signal is masked. Consequently, the studied Jura platform experienced a combination of auto-and allogenic processes, which created a complex facies mosaic and a complex stacking of depositional sequences. Nevertheless, the 100-kyr orbital signal was strong enough to create correlatable sequence boundaries. Within a 100-kyr sequence, however, the unambiguous definition of sequences related to the 20-kyr orbital cycle is often difficult and the prediction of their lateral or vertical facies evolution impossible.

Inside a sediment‐stressed Middle Devonian carpet reef: Cave exposes details of three‐dimensional facies architecture and palaeoecology

“…Lateral facies changes are in part abrupt, and the level of complexity is so high that they cannot be explained by extrinsic factors, such as changes in energy level or water depth. In contrast, the patterns observed are typical of a system controlled by intrinsic parameters (see Walker & Alberstadt, 1975; Trensch & Strasser, 2011, for discussion), including local patterns in energy level, current velocity, seafloor topography and related sedimentation rates. Models from Burgess & Wright (2003) indicate variable regional transport, the development of sediment transport paths and mosaic of carbonate deposits to increase the complexity of reefal architecture.…”

Global, regional and local controls on the development of a Triassic carbonate ramp system, Western Balkanides, Bulgaria

“…The formation of small-scale shallowing-upward sequences in peritidal settings can result from allocyclic (allogenic) and/or autocyclic (autogenic) processes (Strasser, 1991; Tresch & Strasser, 2011). Allocyclic controls are independent of the depositional environment and include orbitally driven eustatic sea-level fluctuations (Goldhammer, Dunn & Hardie, 1987; Strasser et al .…”

“…The relative influence of allocyclic and autocyclic processes is difficult to estimate as they commonly interact (Strasser, 1991; Lehrmann & Goldhammer, 1999; Burgess, 2006; Bosence et al . 2009; Tucker & Garland, 2010; Tresch & Strasser, 2011; Hill et al . 2012; Laya, Tucker & Perez-Huerta, 2013).…”

“…A complex array of different mechanisms and processes controls the growth and demise of marine carbonate depositional systems (Tucker & Wright, 1990; Jones & Desrochers, 1992; Wright & Burchette, 1996; Schlager, 2005; Warrlich, Bosence & Waltham, 2005; Wright & Burgess, 2005; Pomar & Kendall, 2008; Tresch & Strasser, 2011; Williams et al . 2011; Pomar et al .…”