Calcareous algae and Middle Jurassic facies of southern England

Abstract

SummaryThe rarity of calcareous green algae (Order Dasycladales, and family Udoteaceae) in apparently suitable Middle Jurassic facies of southern England is summarized. They are well known from Tethyan areas to the south and opportunities for migration and establishment existed then. It is concluded that tolerance for warm but extra-tropical conditions, which exists in some but not all modern representatives of these algae, has developed gradually since Triassic time and was not well established until Cenozoic time. In Middle Jurassic time few species showed this tolerance, hence the very limited occurrences north of the Tethys.