The Lower Miocene (Aquitanian to ?lower Burdigalian) type locality of the Wiesbaden Formation in the northern region of the Mainz Basin (abandoned ‘Kalkofen Quarry’, Wiesbaden, State of Hesse, Germany) is known to reveal a regressive-dominated sequence encompassing marine, brackish to terrestrial sediments. Our documentation of this depositional setting includes a detailed sedimentological description, geochemical study and palynological analysis of the succession. Our new data suggest significant environmental turnovers such as changes in the siliciclastic fraction and variation from arid to warm humid climatic conditions. Based on macroscopic fossil evidence, we suggest the presence of an autochthonous mangal root system-bearing horizon, with a lateral extent of over 200 sq. m in the uppermost limestone bed of the sequence. Consistent with this, our geochemical analyses indicate subtropical climatic conditions within a marginal marine environment just before the silting up of the coastline. The almost monospecific mass occurrence of hydrobiid gastropods within the root horizon, as well as the algal buildups outcropping in the underlying strata, further point towards a marginal marine to brackish environment, probably with episodic hypersaline conditions. Palynological analysis revealed no mangrove pollen but point to warm and humid climatic conditions. This is the first indication that mangal environments may have existed along the Early Miocene coastline of the northwestern Mainz Basin.