The Down-dip Preferential Sequence Record of Orbital Cycles in Greenhouse Carbonate Ramps

Bádenas, Beatriz; Aurell, Marcos

Abstract

High-frequency sequences of different scales were recorded in the distinct carbonate ramps developed in the Iberian Basin (Spain) in the Jurassic times. This work reviews and compares the sedimentary record of these sequences in four Iberian carbonate ramps: (1) inner-to proximal outer ramp areas of a non skeletal-dominated homoclinal ramp (upper Sinemurian-lowermost Pliensbachian); (2) middle-to proximal outer ramp areas of a skeletal-dominated homoclinal ramp (upper Pliensbachian); (3) shallow to relatively deep domain of a microbial/siliceous sponge-dominated distally steepened ramp (Bajocian); and (4) inner-to open ramp domains of a homoclinal ramp with coral-microbial reefs (upper Kimmeridgian). The comparative review reveals that the sequences were recorded differently from shallow to deep ramp areas. In shallow ramp areas there is a preferential record of eccentricity-related sequences, whereas high-frequency (precession) sequences are ubiquitous in relatively deep ramp settings. This preferential preservation was likely controlled by the interplay between accomodation changes and internal processes controlling accummulation above and below fair-weather and storm wave base levels, rather than by climate (warm vs. cold greenhouse climate modes) and type of carbonate production. Comparison with cyclostratigraphic analysis performed in similar settings indicates that this variable down-dip sequence record seems to be a common feature in greenhouse carbonate ramps: eccentricity-related, meter-thick facies sequences are dominant in shallow ramp areas whereas the deep outer ramp-basin is characterized by preservation of precession or sub-Milankovitch cycles. It is emphasized that the middle to outer ramp sedimentary domain (located around the storm wave base) has the greatest potential for cyclostratigraphic analysis, because this domain is more likely to record both eccentricity- and/or precession-related sequences.

Citation

Bádenas, B., & Aurell, M. (2018). The Down-dip Preferential Sequence Record of Orbital Cycles in Greenhouse Carbonate Ramps. In M. Montenari (Ed.), Stratigraphy & Timescales (285-325). Elsevier. https://doi.org/10.1016/bs.sats.2018.07.002

• Online Publication Date: Aug 29, 2018
• Publication Date: 2018
• Deposit Date: Jun 5, 2023
• Publisher: Elsevier
• Pages: 285-325
• Series Title: Cyclostratigraphy and Astrochronology
• Series ISSN: 2468-5178
• Book Title: Stratigraphy & Timescales
• Chapter Number: 7
• ISBN: 978-0-12-815098-6
• DOI: https://doi.org/10.1016/bs.sats.2018.07.002