摘要
Geomorphological and sedimentological evidence and depositional ages of different geological units in the northern part of the lower Coatzacoalcos River basin suggest the existence of a previously unreported paleolagoon on the southern Gulf of Mexico coast.In this paper,we refer to it as the Coatzacoalcos paleolagoon.We developed a digital elevation model to simulate the accumu-lation of sand sediments that,over time,filled the paleolagoon,an event that began approximately 12,000-10,000 years ago.It collected 22 sediment sam-ples to analyze their grain size distribution,percentage,and color,revealing their affinity in defining the boundaries and shape of theCoatzacoalcospale-olagoon.The grain size distribution was obtained by sieving.The volume-grain size plots revealed differences between the two sediment types:cream-colored sand and red-orange silty sand and clay.Results showed that the sand sediments originated in the Chiapas Massif,which is formed by quartz-rich intrusive igneous rocks(granite and granodiorite)that filled the paleolagoon.Silty sand and clay sediments are present at the boundaries of the paleolagoon,having a distinct origin from the sand.They originate from extrusive igneous rocks of the Sierra de Santa Martha(andesites,andesitic tuffs,and basalts).
