Adomat, F. and Gischler, E., 2015. Sedimentary patterns and evolution of coastal environments during the Holocene in central Belize, Central America.

Coastal lagoons, marshes, and swamps cover large areas of the Belize coast. Twenty-six sediment cores collected along five transects along the central Belize coast and 58 radiocarbon dates from these cores reveal stratigraphic details of coastal sediment deposition. Marine inundation of the mainland and coastal lagoon formation started between 7980 calendar years before present (cal BP) and >5547 cal BP. As a response to sea-level rise during the Holocene transgression, facies retrograded toward the coast, as seen in marginal marine overlying brackish mollusk faunas. Evidence for late Holocene progradation of facies due to sea-level stagnation is largely lacking. The occurrence of landward thinning sand beds, hiatuses, and marine fauna in lagoonal successions are indications of event (overwash) sedimentation. Sediments recovered are largely of Holocene age (<7980 cal BP), overlying Pleistocene sections. Analyses of sediment composition and texture, radiocarbon dating, and mollusk shell identification were used to describe and correlate sedimentary facies. X-ray diffraction analyses have identified quartz as the dominant mineral, with the Maya Mountains as main source of coastal lagoon sediments. The most common sedimentary facies include peat and peaty sediment, mud, sand, and poorly sorted sediments. Pleistocene soil forms the basement of Holocene sediments. Holocene mud represents lagoon background permanent sedimentation. Peats and peat-rich sequences were deposited in mangrove swamp environments, whereas sandy facies mainly occur in the shoreface, beach, barriers, bars, barrier spits, and overwash deposits. Facies successions could be identified for each locality, but it has proven difficult to correlate the stratigraphic sequences, especially among localities. These differences among the five locations studied suggest that apart from regional influence such as sea-level rise, local environmental factors such as small-scale variation in geomorphology and resulting facies heterogeneity, connectivity of the lagoon with the sea, antecedent topography, and river discharge were responsible for coastal sedimentation and lagoon development in the Holocene of Belize.

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