Distribution of phosphorus in the Middle and Upper Ordovician Baltoscandian carbonate palaeobasin

• Main Authors: Leho Ainsaar, Toivo Kallaste, Tarmo Kiipli, Enli Kiipli
• Format: Article
• Language: English
• Published: Estonian Academy Publishers 2010-12-01
• Series: Estonian Journal of Earth Sciences
• Subjects: phosphorus; Ordovician; Baltoscandia; kukersite.
• Online Access: http://www.kirj.ee/public/Estonian_Journal_of_Earth_Sciences/2010/issue_4/earth-2010-4-247-255.pdf

Baltoscandian Middle and Upper Ordovician carbonate rocks are relatively poor in phosphorus, with the P2O5 content of 0.05–0.5%, rarely exceeding 1%. Phosphorus distribution in the Ordovician carbonate succession shows spatial and temporal variations. In the Estonian Shelf P content is the highest in the Middle Ordovician, close to the Tremadocian P-rich siliciclastic sediments, decreasing towards younger carbonate rocks. In the basinal, i.e. deep shelf, sections two intervals of elevated P contents occur: the first is similar to the shallow shelf in the lowermost Darriwilian, the second is a moderate P increase in the upper Darriwilian–Sandbian interval. The Darriwilian–Sandbian interval of elevated P content in the deep shelf sections roughly corresponds to algal kukersite accumulations in the shallow shelf. Multiple processes determined phosphorus distribution in the studied sediments. Regional processes influencing P distribution include seawater circulation, e.g. P influx by coastal upwellings, and sedimentation rate. Global oceanic variation in bioproduction (δ13C trends) had no positive effect on P accumulation in the Baltoscandian epeiric sea.