NSL1 borehole, Soda Lake, Carrizo Plain, San Luis Obispo County, California, USAi

Regional Level Types
NSL1 borehole	Borehole
Soda Lake	Lake
Carrizo Plain	- not defined -
San Luis Obispo County	County
California	State
USA	Country

Paleoredox proxies indicate that the NSL1A core formed in a mainly subreduction environment. The NSL1A core is divided into four zones based on the results of the proxies. Zone 4 (5.0–5.8 m) of the sediment core indicates stable hydroclimatic conditions with low and constant sand and silt content, suggesting a warm and relatively humid environment. Zone 3 (3.35–5.0 m) represents the early half of the Last Glacial Maximum interval and a high lake stand. The elevated sand content suggests postflood events due to the northerly migration of westerly storm tracks. Zone 2 (1.075–3.35 m) reveals nuanced changes, including decreasing salinity, slight increases in wetness, detrital trace metals, and paleoproductivity. These subtle shifts suggest a multifaceted environmental evolution: a trend toward wetter conditions alongside a prolonged shift from cooler to warmer periods. Zone 1 (0.15–1.075 m) spans the Lateglacial to Holocene transition as well as Early and Middle Holocene, marked by significant hydrologic and ecologic variability including rapid warming during the Bølling–Allerød and rapid cooling linked to the Younger Dryas.
The NSL core consists of two drill sites with the core top at an elevation of ~584 masl (meters above sea level) on a portion of the former lake floor, NSL1A and NSL1B. Initial drilling of the lake sediments was obstructed at NSL1A, leading to its abandonment. Subsequently, drilling was carried out roughly two feet from the original location, and core collection began at a depth of 6 m below the ground surface. This second core site, NSL1B, has a total length of approximately 34 m. The total depth for the NSL core is approximately 40 m.

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