Carbonate systems along nutrient and temperature gradients: some sedimentological and geochemical constraints

Abstract

Research over the past several decades has clearly demonstrated that changes in the ocean environment have had major impacts on carbonate systems. Changes in climate, ocean circulation and seafloor spreading rates have influenced temperature and seawater chemistry, including carbonate saturation state and nutrient availability, and thereby have determined boundary conditions for the biota that form carbonate platforms. In turn, the biota determine accumulation rates and facies zonations, thus controlling platform geometry and facies dynamics. In the first section of this paper, we examine how nutrient availability influences carbonate facies associations. We first discuss the role of temperature and nutrient gradients in the modern ocean and their influence on biotic associations. Then we discuss how carbonate sedimentation can be characterized along nutrient gradients. In the second section, we review proxies currently used to reconstruct paleoproductivity in open ocean environments and discuss their applicability to neritic carbonate systems. We highlight the variety of existing proxies and their limitations, and suggest that multiple lines of evidence are needed for valid interpretations. Our short review discusses sedimentological, biogenic, and geochemical proxies that can be used to reconstruct past nutrient fluxes and to constrain paleoceanographic controls over the distribution of carbonate associations. However, it also reveals that more data and case studies are needed that integrate shallow and deep water carbonate sequences and elucidate the links between temperature vs. nutrient supplies changes and facies in ancient carbonate sequences.

Heterozoan carbonates in subtropical to tropical settings in the present and past

“…However, they also occur in the tropics where the oceanographic situation suppresses typical tropical chlorozoan carbonates Simone and Carannante 1988;Hallock et al 1988;Carannante et al 1988). Controls that influence the formation of heterozoan versus chlorozoan carbonates in the tropics include temperature, salinity, water depth, trophic conditions, oxygen and CO 2 concentrations and Mg/Ca ratio in the seawater, alkalinity, morphology and bathymetry of the sea-floor, the type of substrate, transparency of the water column, internal waves and water stratification (Hallock and Schlager 1986;Hallock et al 1988;Carannante et al 1988;Bourrouilh-Le Jan and Hottinger 1988;Stanley and Hardie 1998;Ward 1995, 1999;Pomar 2001a;Mutti and Hallock 2003;Pomar et al 2004;Wright and Burgess 2005). Some of these conditions are strongly influenced by coupled atmospheric and oceanographic circulation patterns.…”

“…The most important biolimiting nutrients for carbonate depositional systems are phosphorous, iron, silica and nitrogen (Brasier 1995a). Nutrients can be introduced into the sedimentary system by several processes including oceanic upwelling, fluvial transport, wind transport and volcanic eruptions (Vogt 1989;Mutti and Hallock 2003;J. Michel, G. Mateu-Vicens, H. Westphal, 2010, Eutrophic tropical carbonate grain associations-the Golfe d'Arguin, Mauritania, submitted).…”

Platform-induced clay-mineral fractionation along a northern Tethyan basin-platform transect: implications for the interpretation of Early Cretaceous climate change (Late Hauterivian-Early Aptian)

“…Then, from the Gerhardtia sartousiana ammonite zone onward, carbonate production took up again on the platforms of the northern Tethys, and this especially in the Vercors and the Helvetic Alps (Arnaud-Vanneau and Arnaud, 1990;Fö llmi et al, 1994Fö llmi et al, , 2006Bodin et al, 2006c); corals, green algae, stromatoporoids and associated rudists recovered in the platform sediments of this period are typical of a photozoan assemblage (e.g., James, 1997;Mutti and Hallock, 2003). During the time of carbonate production in a photozoan mode, the presence of a barrier or a reef that separated the platform from the basin, as well as the morphology of the platform may have led to a fractionation of clay minerals during their transfer to the ocean.…”

Bryozoan beds in northern Italy as a shallow-water expression of environmental changes during the Oligocene isotope event 1

“…While in modern environments phototrophs such as scleractinian corals and larger foraminifera are found in waters with winter surface temperatures above 20°C (James, 1997), bryozoan-bearing heterotrophic communities dominate in cool waters (b 20°C) or in warm settings below the photic zone. Besides water temperature and light penetration, nutrients have an important influence on biotic carbonate production (Hallock and Schlager, 1986;Hallock, 2001;Pomar, 2001;Brandano and Corda, 2002;Mutti and Hallock, 2003;Halfar et al, 2004). While phototrophs, with the exception of red algae, need oligotrophic to slightly mesotrophic conditions to thrive, heterotrophic carbonate producers dominate in nutrient-rich settings (Hallock and Schlager, 1986;Hallock, 2001;Mutti and Hallock, 2003;Halfar et al, 2004Halfar et al, , 2006Wilson and Vecsei, 2005;Westphal et al, 2010).…”