Anatomy and implications of bioturbated beds in black shale sequences: Examples from the Jurassic Posidonienschiefer (Southern Germany)

Journal Article · Tue Aug 01 00:00:00 EDT 1989 · Palaois; (USA)

DOI:https://doi.org/10.2307/3514557· OSTI ID:7154351

Savrda, C E ^[1]; Bottjer, D J ^[2]

---

1. Auburn Univ., AL (USA)
2. Univ. of Southern California, Los Angeles (USA)

Sequences of organic-rich, laminated mudrocks deposited under oxygen-deficient conditions commonly contain interbedded, bioturbated intervals that reflect periodic episodes of improved bottom-water oxygenation. On the basis of differential ichnofossil preservation, many of these redox event beds are divisible into two parts: a primary stratum and a piped zone. Primary strata, characterized by vague burrow mottling and the lack of discrete biogenic structures, represent sediments that have passed through the surface mixed layer. Piped zones, which occur at the interfaces between primary strata and subjacent darker laminated strata, are characterized by well-preserved, discrete trace fossils that represent the earliest emplacement of transition layer burrows in sediments that have not passed through the surface mixed layer. The anatomy of these bioturbated beds can be used to infer the relative durations and magnitudes of the oxygenation events responsible. Based on the thickness of primary strata and the extent of cross-cutting of ishnofossils in the piped zones, two general types or redox events can be recognized: (1) short-term events, and (2) extended events. Systematic increases in burrow diameter, depth of burrow penetration, and diversity of trace-fossil assemblages within piped zones provide evidence for increasing magnitude of oxygenation episodes. The utility and limitations of this approach are illustrated through an example application to twelve bioturbated intervals within black shales of the Jurassic Posidonienschiefer of southern Germany. These beds can be categorized as one of three types, each of which are interpreted to reflect differences in oxygenation-event histories.

• OSTI ID: 7154351
• Journal Information: Palaois; (USA), Vol. 4:4
• Country of Publication: United States
• Language: English

Related Subjects

04 OIL SHALES AND TAR SANDS
FEDERAL REPUBLIC OF GERMANY
OIL SHALE DEPOSITS
PALEONTOLOGY
BLACK SHALES
DEPOSITION
FOSSILS
GEOLOGIC HISTORY
GEOLOGIC STRATA
JURASSIC PERIOD
ORGANIC MATTER
OXIDATION
REDUCTION
THICKNESS
TIME DEPENDENCE
VARIATIONS
BITUMINOUS MATERIALS
CARBONACEOUS MATERIALS
CHATTANOOGA FORMATION
CHEMICAL REACTIONS
DIMENSIONS
ENERGY SOURCES
EUROPE
FOSSIL FUELS
FUELS
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC FORMATIONS
GEOLOGIC STRUCTURES
MATERIALS
MESOZOIC ERA
MINERAL RESOURCES
OIL SHALES
RESOURCES
WESTERN EUROPE
040200* - Oil Shales & Tar Sands- Reserves
Geology
& Exploration