calcite sea
...that carbonate hardgrounds were most commonly formed during calcite sea intervals in the Ordovician and Jurassic periods in Earth's history, but were virtually absent from the aragonite seas of the Permian era?
...that <a href="./Carbonate_hardgrounds" id="mwF8c" rel="mw:WikiLink" title="Carbonate hardgrounds">carbonate hardgrounds</a> were most commonly formed during <b id="mwF8g"><a href="./Calcite_sea" id="mwF8k" rel="mw:WikiLink" title="Calcite sea">calcite sea</a></b> intervals in the <a href="./Ordovician" id="mwF8o" rel="mw:WikiLink" title="Ordovician">Ordovician</a> and <a href="./Jurassic" id="mwF8s" rel="mw:WikiLink" title="Jurassic">Jurassic</a> <a class="mw-redirect" href="./Period_(geology)" id="mwF8w" rel="mw:WikiLink" title="Period (geology)">periods</a> in <a href="./Earth" id="mwF80" rel="mw:WikiLink" title="Earth">Earth</a>'s history, but were virtually absent from the <a href="./Aragonite" id="mwF84" rel="mw:WikiLink" title="Aragonite">aragonite</a> seas of the <a href="./Permian" id="mwF88" rel="mw:WikiLink" title="Permian">Permian</a> era?