BH250-239
Title
BH250-239
Subject
Diamictite/Breccia
Description
Major Minerals: calcite, quartz, oxides
The diamictite exposed in Death Valley is part of the well-known Neoproterozoic glacial deposits preserved throughout the region. These rocks are associated with the Kingston Peak Formation, a unit famous for recording dramatic environmental change during the Cryogenian Period, when Earth may have experienced the extreme global glaciations known as Snowball Earth.
These diamictites are coarse, poorly sorted sedimentary rocks composed of a muddy to sandy matrix containing scattered pebbles, cobbles, and angular to rounded clasts of many rock types. In outcrop they can resemble breccia, especially where clasts are angular and locally derived. Their mixed texture suggests deposition by high-energy mass flows, debris flows, or glacial processes. Geologists interpret the Kingston Peak diamictite as the product of glaciers descending from uplifted highlands into marine basins, dropping unsorted debris into water or generating subaqueous debris flows.
The age of these deposits is Cryogenian (about 720–635 million years old), corresponding to the two major global glaciations: the Sturtian (~717–660 Ma) and Marinoan (~650–635 Ma). Death Valley preserves one of the best North American records of these intervals. These glacial episodes may have covered much of Earth’s surface with ice, even extending into tropical latitudes, hence the term Snowball Earth.
Comparable Cryogenian diamictites are also preserved in the Tambien Group of Tigray Ethiopia, where they record the lead-up to and onset of Sturtian glaciation along the northern margin of the Arabian-Nubian Shield. Integrated stratigraphy, chemostratigraphy, and geochronology from these Ethiopian successions have provided some of the most important age constraints on Snowball Earth events. U-Pb zircon ages and carbon-isotope data indicate that environmental instability and major carbon-cycle perturbations preceded the Sturtian glaciation, with critical dates clustering around 719 million years ago, just prior to global ice advance. Key studies by Yuem Park, Nicholas L. Swanson-Hysell, Scott A. MacLennan, Adam C. Maloof, Bereket Haileab and collaborators (2015, 2018, 2019) demonstrated globally synchronous carbon-isotope change and helped constrain the timing of the Sturtian Snowball Earth.
These rocks are especially important because they record a turning point in Earth history. Immediately above some glacial diamictites worldwide are “cap carbonates,” unusual carbonate layers deposited during rapid greenhouse warming after global ice retreat. These strata mark profound shifts in ocean chemistry, atmospheric CO₂, and early biological evolution.
The diamictite exposed in Death Valley is part of the well-known Neoproterozoic glacial deposits preserved throughout the region. These rocks are associated with the Kingston Peak Formation, a unit famous for recording dramatic environmental change during the Cryogenian Period, when Earth may have experienced the extreme global glaciations known as Snowball Earth.
These diamictites are coarse, poorly sorted sedimentary rocks composed of a muddy to sandy matrix containing scattered pebbles, cobbles, and angular to rounded clasts of many rock types. In outcrop they can resemble breccia, especially where clasts are angular and locally derived. Their mixed texture suggests deposition by high-energy mass flows, debris flows, or glacial processes. Geologists interpret the Kingston Peak diamictite as the product of glaciers descending from uplifted highlands into marine basins, dropping unsorted debris into water or generating subaqueous debris flows.
The age of these deposits is Cryogenian (about 720–635 million years old), corresponding to the two major global glaciations: the Sturtian (~717–660 Ma) and Marinoan (~650–635 Ma). Death Valley preserves one of the best North American records of these intervals. These glacial episodes may have covered much of Earth’s surface with ice, even extending into tropical latitudes, hence the term Snowball Earth.
Comparable Cryogenian diamictites are also preserved in the Tambien Group of Tigray Ethiopia, where they record the lead-up to and onset of Sturtian glaciation along the northern margin of the Arabian-Nubian Shield. Integrated stratigraphy, chemostratigraphy, and geochronology from these Ethiopian successions have provided some of the most important age constraints on Snowball Earth events. U-Pb zircon ages and carbon-isotope data indicate that environmental instability and major carbon-cycle perturbations preceded the Sturtian glaciation, with critical dates clustering around 719 million years ago, just prior to global ice advance. Key studies by Yuem Park, Nicholas L. Swanson-Hysell, Scott A. MacLennan, Adam C. Maloof, Bereket Haileab and collaborators (2015, 2018, 2019) demonstrated globally synchronous carbon-isotope change and helped constrain the timing of the Sturtian Snowball Earth.
These rocks are especially important because they record a turning point in Earth history. Immediately above some glacial diamictites worldwide are “cap carbonates,” unusual carbonate layers deposited during rapid greenhouse warming after global ice retreat. These strata mark profound shifts in ocean chemistry, atmospheric CO₂, and early biological evolution.
Coverage
Location: Death Valley, California, USA
Nearby Geographic Feature: Death Valley
GPS Coordinates: 35.820258, -116.090953
Nearby Geographic Feature: Death Valley
GPS Coordinates: 35.820258, -116.090953
Date
2023
Creator
Bereket Haileab
Source
From the rock collection of Bereket Haileab. Sample 239. Housed at Carleton College in Minnesota.
Type
Thin section and hand sample
Relation
Collection
Citation
Bereket Haileab, “BH250-239,” BH250 Mineralogy Teaching Collection, accessed April 24, 2026, https://bereket-haileab.geology.sites.carleton.edu/items/show/312.