BH250-236
Title
BH250-236
Subject
Shale (red)
Description
BH250-236, exposed at 35.700839, -116.250706 in eastern Death Valley, is part of a shale, siltstone, and probable turbidite sequence that lies beneath the diamictite and is most likely within the lower Kingston Peak Formation, or within a transitional interval immediately below one of its glacially influenced diamictite units. This formation is one of the most significant Neoproterozoic successions in western North America because it preserves evidence of major environmental and tectonic change during the Cryogenian Period, approximately 720–635 million years ago. In many parts of Death Valley, the Kingston Peak Formation consists of repeated alternations of fine-grained shale and siltstone with coarser sandstone and diamictite, reflecting shifting basin conditions through time.
The shale beds were likely deposited in relatively quiet water, where clay and fine mud slowly settled onto the floor of a marine basin or restricted rift trough. The siltstones indicate occasional higher-energy pulses that transported somewhat coarser sediment into the basin. If the outcrop displays graded bedding, thin repetitive layers, fining-upward beds, or erosional soles, these rocks were probably deposited as turbidites (see photos), sediment laid down by underwater density currents or submarine avalanches moving downslope into deeper water. Such deposits suggest that nearby basin margins were tectonically active and periodically shed sediment into deeper parts of the basin, an interpretation also noted by Mike Smith, Class of 1999 (personal communication).
The diamictite (BH250-239) above marks a dramatic shift in depositional style. Whereas the shale and siltstone below record relatively calm marine sedimentation interrupted by turbidity flows, the overlying diamictite represents sudden emplacement of poorly sorted coarse debris. In the Kingston Peak Formation, these diamictites are commonly interpreted as products of Cryogenian glaciation, submarine debris flows, or glacially derived sediment reworked into marine basins. Their presence above the finer-grained beds may record the onset of colder climatic conditions, uplift of surrounding highlands, or increasing basin instability during regional rifting.
This outcrop preserves a fascinating transition from quiet-water basin sedimentation to high-energy glacial or mass-flow deposition more than 700 million years ago, capturing an important chapter in the tectonic and climatic evolution of the late Precambrian Earth.
The shale beds were likely deposited in relatively quiet water, where clay and fine mud slowly settled onto the floor of a marine basin or restricted rift trough. The siltstones indicate occasional higher-energy pulses that transported somewhat coarser sediment into the basin. If the outcrop displays graded bedding, thin repetitive layers, fining-upward beds, or erosional soles, these rocks were probably deposited as turbidites (see photos), sediment laid down by underwater density currents or submarine avalanches moving downslope into deeper water. Such deposits suggest that nearby basin margins were tectonically active and periodically shed sediment into deeper parts of the basin, an interpretation also noted by Mike Smith, Class of 1999 (personal communication).
The diamictite (BH250-239) above marks a dramatic shift in depositional style. Whereas the shale and siltstone below record relatively calm marine sedimentation interrupted by turbidity flows, the overlying diamictite represents sudden emplacement of poorly sorted coarse debris. In the Kingston Peak Formation, these diamictites are commonly interpreted as products of Cryogenian glaciation, submarine debris flows, or glacially derived sediment reworked into marine basins. Their presence above the finer-grained beds may record the onset of colder climatic conditions, uplift of surrounding highlands, or increasing basin instability during regional rifting.
This outcrop preserves a fascinating transition from quiet-water basin sedimentation to high-energy glacial or mass-flow deposition more than 700 million years ago, capturing an important chapter in the tectonic and climatic evolution of the late Precambrian Earth.
Coverage
Location: Death Valley, California, USA
Nearby Geographic Feature: Death Valley
GPS Coordinates: 35.700839, -116.250706
Nearby Geographic Feature: Death Valley
GPS Coordinates: 35.700839, -116.250706
Date
2023
Creator
Bereket Haileab
Source
From the rock collection of Bereket Haileab. Sample 236. Housed at Carleton College in Minnesota.
Type
Thin section and hand sample
Relation
Collection
Citation
Bereket Haileab, “BH250-236,” BH250 Mineralogy Teaching Collection, accessed October 22, 2026, https://bereket-haileab.geology.sites.carleton.edu/items/show/309.