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Trophic resources are an important control governing carbonate production. Though this importance has long been recognized, no calibration exists to quantitatively compare biogenic assemblages within trophic resource fields. This study presents a field calibration of carbonate producers in a range of settings against high-resolution in situ measurements of nutrients, temperature and salinity. With its latitudinal extent from 30°to 23°N, the Gulf of California, Mexico, spans the warm-temperate realm and encompasses nutrient regimes from oligo-mesotrophic in the south to eutrophic in the north. Accordingly, from south to north carbonates are characterized by: (i) coral-dominated shallow carbonate factories (5-20 m water depth) with average sea-surface temperatures of 25°C (min. 18°C, max. 31°C), average salinities of 35AE06& and average chlorophyll a levels, which are a proxy for nutrients, of 0AE25 mg Chl a m )3 (max. 0AE48, min. 0AE1). (ii) Red algal-dominated subtidal to inner-shelf carbonate formation (10-25 m) in the central Gulf of California exhibiting average temperatures of 23°C (min. 18°C, max. 30°C), average salinities of 35AE25&, and average Chl a levels of 0AE71 Chl a m )3 (max. 5AE62, min. 0). (iii) Molluskan bryozoan-rich inner to outer shelf factories in the northern Gulf of California (20-50 m) with average sea surface temperatures of only 20°C (min. 13°C, max 29°C), average salinities of 35AE01&, and average contents of 2AE2 mg Chl a m )3 (max. 8AE38, min. 0). By calibrating sedimentological data with in situ measured oceanographic information in different environments, the response of carbonate producers to environmental parameters was established and extrapolated to carbonates on a global scale. The results demonstrate the importance of recognizing and quantifying trophic resources as a dominant control determining the biogenic composition and facies character of both modern and fossil carbonates.

[1] In order to determine the sensitivity of coastal upwelling tracers to seasonal wind forcing and El Niño-Southern Oscillation (ENSO) off Baja California and Chile, nearshore salinity, cadmium (Cd), and nutrients phosphate, silicate, nitrate+nitrite were monitored in surf zone waters at six locations along the North and South American coasts during 1997-2000. The clearest responses to upwelling favorable wind forcing were observed at the southern tip of Baja California (23.3°N) and off central-southern Chile (36.5°S). Upwelling tracers at 23.3°N were also the most sensitive to El Niño: average summer Cd and nutrient enrichments were 60% lower following El Niño than during the previous non-El Niño upwelling season. At two sites on the northern and central Chile coasts, conditions associated with El Niño resulted in salinity anomalies >1. Such large shifts in nearshore water properties suggest it may be possible to reconstruct past ENSO patterns from geochemical paleonutrient/paleosalinity proxy records preserved in nearshore archives such as mollusc or foraminifera shells. INDEX TERMS: 4215

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