Understanding the provenance and production process of historic mortars—a novel approach employing calcareous nannofossils

Abstract Limestones (CaCO 3 ) have been an important source for masonry and mortars throughout approx. 10,000 years of human history. They are often composed calcitic shells minute marine algae, known as calcareous nannofossils. The 0.25–30-µm large skeletons these primary producers well documented from various archaeological materials including building stones masonry. Surprisingly, tiny microfossils were recently also observed in medieval mortar-based materials, even though the carbonate-based rocks heated kilns quicklime production. Burning experiments carbonate-rich sedimentary rocks, containing well-preserved abundant nannofossils, a deteriorating preservation decrease diversity relative abundance nannofossils with increasing temperatures. Alongside lime-based binder historic contain under- overburnt lime lumps aggregates; latter added after heating process. Lime aggregates offer additional, so far not yet fully understood information on burning Here, studied ultra-thin sections mortars, resulting separate analysis binder, aggregates. findings allow (i) more precise provenance limestones (ii) accurate reconstruction temperatures reached during Our study thus improves approach sheds light technology mortar production by using