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The research on Quaternary geology in Tianjin Center has been experienced two stages divided approximately in the middle of 1980s. The first phase was mainly focused on the Quaternary glacio-stratigraphical study, while the second had being gradually oriented to the coastal geological investigations and study as well. This paper reviews succinctly the profound achievements in the field of fundamental researches, including litho- , bio- and chronostratigrahies and applied geology serving for the coastal ecosocietal development. Then, taking the local marine regressive processes as a case study, this paper re- emphasizes the hypothesis of‘Barrier- island- lagoon cause’for the land formation of Bohai Bay. Based on multi- disciplinary approaches on sea- level change, stratigraphic significance of the existing sea- level indicators, microgeomophology and chronology, we found : (1) The RMSLc (corrected relative mean sea level) belt is to fall into the global ESL (ice-volume equivalent sea level) belt or even slightly higher than the latter after eliminating the local subsidence caused by the groundwater withdrawal. It suggests that the regional isostatic uplift can fully offset the local subsidence given by both neotectonics and self- compaction. As a result, a configuration of the palaeo altitudes of being formed land following marine regression since the last ~7 ka have been basically under the simultaneous tidal water influences and, thus, it provides a precondition for the‘Berrier- island- Lagoon System’of the study area. (2) The muddy mounds, found in the Chenier Plain, are equivalent to the muddy mounds of the Oyster Reef Plain and can be characterized as the‘muddy cheniers’. Both shelly and muddy cheniers altogether form a number of the palaeo barrier- shaped shorelines. Based on our previous study, this paper re-depicts a temporo-spatial distribution of the regional palaeoshorelines under such a new concept of the shelly-muddy cheniers. (3) A coastal wetland, ~30 km wide apart in between the maximum marine transgression boundary and the oldest morphologically- remarkable shoreline (a linkage of the Chenier V and the Muddy Mound Shizhuang- Dongjituo- Mengzhuang), with time span ~7- 4.5 ka, should be attributed to the‘Palaeo Lagoon I’. Afterwards, following periodically formed barrier shorelines, new lagoons may disconsecutively occur behind the each barrier shoreline simultaneously and/or even obviously later (The younger high waters may even farther pour into those previously older lagoons). This cyclicity is thus a basic characteristic of the area and is an essential feature named Canghaisangtian, i.e., seas change into mulberry fields. (4) Although such processes have been greatly impacted by human activities during the past two centuries, facing to the predicted coming rise of sea level this century and potential environmental deterioration (ground subsidence, landward- reversed groundwater table, etc.), this paper forecasts the Barrier- island- Lagoon environment will reappear obviously again in the coming future. Fortunately, the geographical layout of‘Green Coastal Defence Belt’perfectly tallies with the aforementioned cyclicity and the youngest lagoonal area. Nevertheless, it is necessary to re- examine closely this urban plan under the geologic evolution point of view and better to further aggrandize its strategic position in order to meet the mid- and long time scale coastal sustainability.
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