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Abstract

Stratigraphic shifts in the oxygen isotopic (δ 18 O) and trace element (Mg and Sr) composition of biogenic carbonate from tropical lake sediment cores are often interpreted as a proxy record of the changing relation between evaporation and precipitation (E/P). Holocene δ 18 O and Mg and Sr records from Lakes Salpetén and Petén Itzá, Guatemala were apparently affected by drainage basin vegetation changes that influenced watershed hydrology, thereby confounding paleoclimatic interpretations. Oxygen isotope values and trace element concentrations in the two lowland lakes were greatest between ~ 9000 and 6800 14 C-yr BP, suggesting relatively high E/P, but pollen data indicate moist conditions and extensive forest cover in the early Holocene. The discrepancy between pollen-and geochemically-inferred climate conditions may be reconciled if the high early Holocene δ 18 O and trace element values were controlled principally by low surface runoff and groundwater flow to the lake, rather than high E/P. Dense forest cover in the early Holocene would have increased evapotranspiration and soil moisture storage, thereby reducing delivery of meteoric water to the lakes. Carbonate δ 18 O and Mg and Sr decreased between 7200 and 3500 14 C-yr BP in Lake Salpetén and between 6800 and 5000 14 C-yr BP in Lake Petén Itzá. This decline coincided with palynologically documented forest loss that may have led to increased surface and groundwater flow to the lakes. In Lake Salpetén, minimum δ 18 O values (i.e., high lake levels) occurred between 3500 and 1800 14 C-yr BP. Relatively high lake levels were confirmed by 14 C-dated aquatic gastropods from subaerial soil profiles ~1.0 -7.5 m above present lake stage. High lake levels were a consequence of lower E/P and/or greater surface runoff and groundwater inflow caused by human-induced deforestation.

Quantification of soil erosion rates related to ancient Maya deforestation

“…In this study, we combined information from seismic data with accelerator mass spectrometry (AMS) 14 C radiocarbon dates on lake sediment cores. We dated only terrestrial organic matter, enabling us to obtain a reliable sediment chronology (Rosenmeier et al, 2002a(Rosenmeier et al, , 2002b; see GSA Data Repository Fig. DR1 1 ).…”

“…All presented depths refer to this composite depth scale. Four main lithologic units were defi ned (L1-L4) on the basis of changes in sediment composition and chemistry (Rosenmeier et al, 2002b). Lithologic units were recognized by sharply contrasting organic matter content, as expressed by total organic carbon (TOC) concentrations (Fig.…”

“…Sediment volumes were converted to dry sediment mass using a grain density of 2.5 g/cm 3 and average porosities of 90% and 70% for gyttja and clay, respectively, on the basis of empirical measurements in several Salpetén cores (Rosenmeier et al, 2002b). Using the seismic to core correlation and AMS 14 C age model (Rosenmeier et al, 2002a(Rosenmeier et al, , 2002bFig. 2; Table DR2 and Fig.…”

Considering lacustrine erosion records and the De Ploey erosion model in an examination of mountain catchment erosion susceptibility and precipitation reconstruction

“…The representation of vegetation cover, described in Table 3 (and Table 1) as 'indicative small tree % vegetation cover', is derived from the corrected pollen vegetation reconstruction in the temporal datasets. This catchment characteristic correlated with Es C values, suggesting that the erosion susceptibility in the temporal dataset may follow similar trends and illustrating the known driving influence of vegetation cover and change on erosion (Noël et al, 2001;Rosenmeier et al, 2002). Allen et al Catena xxx (xxxx) xxx-xxx…”

The Apparent Resilience of the Dry Tropical Forests of the Nicaraguan Region of the Central American Dry Corridor to Variations in Climate Over the Last C. 1200 Years

“…These formations are primarily distributed according to climate (temperature and precipitation), soil type (e.g., volcanic, alluvial), and elevation (highlands and lowlands). Past [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] and the transition between the two [21]. These changes in hydroclimate are reported to be primarily driven by the interactions of three climatic forces: (i) the position of the Inter Tropical Convergence Zone (ITCZ); (ii) the North Atlantic Oscillation; and (iii) the El Niño Southern Oscillation (ENSO) [22].…”