Rare travertine systems in Jordan: evolution, chemical and biogenic composition

This study examines two rare travertine systems in Jordan, shedding light on distinctive hydrogeochemical and environmental processes. Uniquely, the Maqarin travertines form through absorption of atmospheric CO₂, interacting with oil shale and leading to the precipitation of distinctive biogenic-rich travertine, unlike most travertines that form by CO₂ degassing. In Maqarin, hyper-alkaline spring waters (pH > 12) absorb atmospheric CO₂ and react with oil shale to precipitate biogenic-rich travertine. In contrast, the Zarqa Ma'in–Zara region hosts thermal springs emerging from sandstone aquifers that are either enriched or depleted in trace metals, producing stratified travertine facies with varied mineralogy and colours (black, brown, whitish). Analyses of fabric, fossils, and depositional features show that groundwater evolution, microbial activity, and seasonal changes control travertine precipitation. These deposits record dynamic water–rock interactions, tectonic activity, past climate, and biological influence, based on this study's findings and supported by previous research, enhancing understanding of travertine formation in complex geological settings.