USGS Open-File Report 01-282 -- Table 2

Open-File Report 01-282

Sediment-Deposition Rates and Organic Compounds in Bottom Sediment at Four Sites in Lake Mead, Nevada, May 1998

Table 2. Physical characteristics of bottom-sediment cores at four sites in Lake Mead, May 1998

[Abbreviation: cm, centimeter. Symbol: --, not reported]

Characteristics	Site 1: Las Vegas Bay, shallow -- length of core below lake bottom (cm)
Characteristics	Top 0-15	15-27	27-36	36-100	100-114	Bottom 114-125
Water content	Saturated	Saturated	Medium saturation	Medium saturation	Minimal saturation	Minimal saturation
Particle size	Medium silt-clay mix with fine-grained sand	Medium silt with fine-grained sand	Medium silt with small amounts of fine-grained sand	Medium silt with small amounts of clay	Medium silt	Fine to coarse sand
Color¹	Pale yellow-brown, olive gray	Olive gray	Grayish black and olive gray	Olive gray	Light olive-brown	Light brown
Odor	--	--	--	--	--	--
Special comments	No benthos or organic debris	No benthos or organic debris	Fine grain sand	Crumbly texture, very homogenous	Stiff silt texture	Pre-impoundment deposition layer at 116 cm

Characteristics	Site 2: Las Vegas Bay, deep -- length of core below lake bottom (cm)
Characteristics	Top 0-41	41-75	75-105	105-115	115-120	120-130	130-140	Bottom 140-150
Water content	Saturated	Saturated	Medium saturation	Medium saturation	Medium saturation	Medium saturation	Medium saturation	Medium saturation
Particle size	Medium to fine silt	Medium silt, fine clay	Moderate clay, fine silt	Moderate clay, fine silt	Moderate clay, fine silt	Fine to coarse sand	Coarse sand	Coarse sand to gravel
Color¹	Olive-gray, light brown	Olive-gray	Olive-gray	Olive-gray	Light olive-brown	Light olive-brown	Light olive-brown	Light olive-brown
Odor	--	--	--	--	--	--	--	--
Special comments	No benthos or organic debris	No benthos or organic debris	75-80 cm disturbed during core dissection	Distinct color change from light olive to olive	Fine sand layer, Pre-impoundment deposition layer at 118 cm	--	--	Gravel sizes up to 2 cm in diameter

Characteristics	Site 3: Overton Arm -- length of core below lake bottom (cm)
Characteristics	Top 0-12	12-19	19-35	35-60	60-70	70-73	Bottom 73-85
Water content	Saturated	Saturated	Medium saturation	Medium saturation	Medium saturation	Minimal saturation	Minimal saturation
Particle size	Medium silt	Medium silt with minimal fine-grained sand	Medium silt with minimal fine-grained sand	Medium silt with minimal fine-grained sand	Medium silt, minimal clay	Clay	Firm clay to medium-coarse sand
Color¹	Yellow brown	Gray brown and olive gray	Brown	Olive black with brown stripes	Olive gray with brown stripes	Brown	Brown
Odor	--	--	--	--	--	--	--
Special comments	No benthos or organic debris, homogenous texture	Corbicula fluminea alive at 18 cm	Corbicula fluminea dead at 25 cm	Smooth, homogenous texture, no organic debris	Smooth, homogenous texture	Stiff texture	Pre-impoundment deposition layer at 75 cm

Characteristics	Site 4: Colorado and Virgin Rivers confluence (pre-impoundment) -- length of core below lake bottom (cm)
Characteristics	Top 0-5	5-16	16-21	21-45	45-70	70-85	Bottom 85-147
Water content	Saturated	Medium saturation	Medium saturation	Minimal saturation	Minimal saturation	Minimal saturation	Minimal saturation
Particle size	Silt with minimal fine sand	Silt	Silt	Silt	Silt	Medium silt, fine sand, clay	Medium to fine sand
Color¹	Yellowish brown	Yellowish range with brown stripes	Brown-black with yellowish stripes and olive-black stripes	Gray-black with olive-black stripes and yellowish brown stripes	Olive-gray with brown-gray stripes and yellowish brown stripes	Olive-gray with brown-gray stripes and yellowish brown stripes	Yellow-brown with olive-gray stripes
Odor	--	Medium hydrogen sulfide odor	Minimal hydrogen sulfide odor	Medium hydrogen sulfide odor	Minimal hydrogen sulfide odor	Minimal hydrogen sulfide odor	--
Special comments	Very fluid texture	Soft texture	Smooth texture	No benthos or debris, smooth texture	Smooth texture	Fine sand layer	Pre-impoundment deposition layer at 85 cm

¹Rock color chart (Geological Society of America, 1991).