Burrow Preservation Research Articles

Influence of hypoxia on biogenic structure in sediments on the Louisiana continental shelf

As part of a study of the effects of seasonal hypoxia on sediment properties, samples were collected during the spring and late summer of 2009 from four sites of similar sediment type and water depth (30–39 m), but different recent history of bottom water oxygen concentration on the continental shelf of Louisiana. Sediment profile imaging (SPI), box coring, X-radiography, and computed tomography (CT) imaging were employed to characterize the biogenic structural differences in surficial sediments among a normoxic control site and three sites subjected to hypoxic events varying in frequency of occurrence. Results of the CT imagery indicated that macrobenthic biogenic structures were the most numerous at the H7 site that had experienced the least hypoxia in the past 23 years. The E4 site that had experienced hypoxia seasonally with a frequency between 50% and 75% of the time had the fewest biogenic structures in spring 2009, but exhibited recovery in terms of their abundance and diameter in summer 2009. E4 also exhibited high rates of bioturbation during the late-summer sampling as determined from excess 234Th. This suggests that the macrobenthos community at this site was in an active phase of recovery from hypoxia. At the A6 site, exposed to hypoxia with an annual frequency ≥75%, biogenic structures were numerous but dimensionally small, correlating with the average individual size of macrobenthos found there. The total volume maxima occupied by biogenic structures in the sediment occurred below the uppermost sediment intervals, with the exception of the spring sample from the D5 site that experienced hypoxia between 25% and 50% of the time. CT-imagery indicating effects of seasonal hypoxia on biogenic structure in the top 10 cm of sediments detected more structures than SPI, X-radiographic imagery, or macrobenthos census data. The presence of relict burrows probably inflated estimates of biogenic structures in the subcores, rendering an integrated result that included creation, destruction, and preservation of burrows and voids over time.

Interactions between Ediacaran animals and microbial mats: Insights from Lamonte trevallis, a new trace fossil from the Dengying Formation of South China

A new ichnogenus and ichnospecies, Lamonte trevallis, is formally described from the Shibantan Member limestone of the upper Ediacaran Dengying Formation, Yangtze Gorges area, South China. It is characterized by horizontal tunnels connected with short vertical burrows and surface trails. The horizontal burrows are elliptical or bilobed in transverse cross-section, preserved in full relief, and filled with carbonate intraclasts, micrites, as well as calcite and silica cements. They occur exclusively in silty, crinkled, and microlaminated layers that are interpreted as amalgamated cyanobacterial microbial mats; no burrows have been found in intraclastic layers adjacent to the microlaminated layers. The vertical traces are filled with the same material as the burrows, but they typically project through the crinkled microlaminae and are exposed on the bedding surface. The surface tracks are always preserved in negative epirelief or positive hyporelief and consist of two parallel series of either sharp scratch marks or small knobs. The burrow infill has δ18Ocarb and δ13Ccarb values distinct from, but intermediate between, microlaminated and intraclastic layers, consistent with petrographic observation that burrow infill consists of a mixture of early carbonate cements, intraclasts, and micrites. Bedding plane bioturbation intensity (20–40%)—measured as percentage of bedding plane area covered by L. trevallis traces—is comparable to similar measurements in pre-trilobite Cambrian carbonates. The exclusive occurrence of L. trevallis within microbial mats may have both taphonomic and ecological significance. These mats may have provided firm substrates and localized geochemical conditions that contributed to the structural integrity of the burrows, and they may have also facilitated early diagenetic cementation of burrow infill, thus facilitating burrow preservation. The close association of these burrows with microbial mats implies that the trace producers actively mined cyanobacterial mats to exploit oxygen or nutrient resources. The trace makers of L. trevallis were better able to utilize the resources around them than many other Ediacaran trace makers and provide an ichnological record of a flourishing benthic ecology in late Ediacaran oceans at the dawn of the agronomic revolution.

Microorganism-mediated preservation of Planolites, a common trace fossil from the Harkless Formation, Cambrian of Nevada, USA

Specimens of Planolites, a tubular ichnofossil, from the Harkless Formation (Cambrian of Nevada) are commonly rimmed by thin layers of limonite, a probable pseudomorph after pyrite, suggesting that bacterially induced biomineralization played a key role in the preservation of the burrows. Organic material secreted by a vermiform, infaunal tracemaker is inferred to have formed the substrate for a biofilm that facilitated iron sulfide biomineralization by bacteria under localized anaerobic or dysaerobic conditions. Rapid, microbially mediated biomineralization of mucus-lined burrow walls is inferred to have promoted three-dimensional preservation of burrows by strengthening them against sediment compaction, and possibly providing sufficient support for burrows to allow time for sediment infill. Decomposition of organic materials in Planolites also left evidence in sediment layers immediately above the burrows: undulose sediment surfaces and small, round, pimpleform gas escape structures.

Biophysical Model of Intertidal Beach Crab Burrowing:Application and Significance

The biophysical principles and mechanisms involved in intertidal beach-crab burrowing have been studied. These answer some important and fundamental questions, such as how and what basic burrow patterns evolve in dynamic environmental conditions through a delicate balance struck between physical and biological (ethological) processes, and how does a burrow form faithfully record its environmental history in a sedimentary sequence? The study is primarily based on field and experimental data collected on the amphibious brachynuran crab family Ocypodidae (four species of Ocypodeand one species of Ilyoplax) from modern intertidal beach sectors on the Bay of Bengal coast, India. The model introduces a new concept of crab burrow cycle that includes three phases and involves three genetic categories of burrow forms—occupied, abandoned, and collapsed. The first phase (subaerial) begins with the excavation of simple (I or J types) occupied burrow populations and terminates with the development of plugged burrow apertures and sub-surface trapped air-column systems. Pressure equilibrium is reached between the burrow-base capillary water, air columns and sediment plugs. Formation of an air column is a mechanical means of supporting hollow burrow from collapse and creating an underwater quasi-terrestrial condition of living. The second phase (subaqueous) starts with tidal inundation and results in the final burrow architecture (Y, U, multibranched Y, and multiform U). The continued effects of external dynamic pressure fields on the plugs increases the internal air-column pressure causing pressure disequilibrium and lowering of capillary water levels unfavorable to the crabs for gill respiration. The burrower neutralizes the extra pressure to achieve previous pressure equilibrium and capillary water levels by excavating secondary branch(es) advantageously on the landward side of the main shaft and dumping the materials at the burrow-base. This mechanism, besides adding morphological complexities, ensures continued pressure equilibrium, the failure of which in any stage results in burrow collapse. The third phase (subaerial) creates a permanent pressure imbalance as the tidal water quickly recedes and protects the burrower inside as the air column bursts to set the crab free to start another burrow cycle afresh. The model has application potential in varied post-Jurassic coastal intertidal environmental settings occupied by quasiterrestrial crabs. It provides insight into various aspects of ichnology (taxonomy and recognition of ancient crab burrows; characterization and variability of the Psilonichnusichnofacies and intertidal ichnocoenoses; burrowing life habits of crabs and modalities of burrow preservation), environment (influence of bathymetry, tide and wave action, substrate properties, storm-induced episodic erosion and deposition on burrow architecture; environmental zonation of burrows; paleotidal range and marine transgression-regression events) and geomorphology (recognition of shoreline features). Being the first biophysical model of intertidal crab burrows, it contributes original data to the theoretical background of ichnology.

Use of axial tomography to follow temporal changes of benthic communities in an unstable sedimentary environment (Baie des Ha! Ha!, Saguenay Fjord)

In the upper layer of the sediment column, organic matter recycling is greatly influenced by bioturbation. However, there are many physical changes in the nature of the sediment that may disturb benthic communities and create a biogeochemical imbalance. Following a very heavy rainfall between 26 and 29 July 1996, an intense flash flood in the Saguenay Fjord caused discharges of 6 million cubic metres of sediments into Baie des Ha! Ha!. Unstable sediment deposits located at the top of the delta of the Rivière des Ha! Ha! were sporadically exported to the deep basin. After this physical disturbance, meiobenthic and macrobenthic organisms progressively re-colonised the sediment column. To determine the impacts of such sedimentary depositions on benthic fauna, two stations, one at the head and one at the mouth of the Baie des Ha! Ha!, have been monitored since 1996. During this survey, we developed a new method for the quantification of biogenic structures using computer axial tomography (CAT-Scan). Benthic fauna analysis showed that the two stations were characterised by different temporal changes in the benthic dynamics according to their geographic location. Using CAT-Scan analysis of sediment cores, we were able to characterise the stability of the sediment column for the two stations in 1999 and 2000. Scan results suggest that colonisation processes were closely linked with the stability of the sediment column. Erosion and re-deposition of surficial sediments caused a succession in the formation of biogenic structures. These variations were characterised for the first time using CAT-Scan, which is a nondestructive, rapid, and precise method. Tomographic analysis showed the importance of the production and destruction rates of biogenic structures and the sedimentation rate for the preservation of burrows and potentially reactive components. This study finally demonstrated that each erosional event could be followed by a rapid formation of biogenic structures, allowing the re-oxidation of old deposits.

Firmground Ichnofabrics in Deep-water Sequence Stratigraphy, Tertiary Clinoform-toe Deposits, New Jersey Slope

Abstract Sixteen erosional surfaces are recognized in a 144-m-thick condensed package of Tertiary (Eocene-Pliocene) clinoform-toe sediments recovered at ODP Site 1073 on the New Jersey slope. Most of these surfaces are associated with significant hiatuses or extremely condensed intervals defined by Sr isotopes or biostratigraphic data, and many can be linked to sequence boundaries defined in onshore and shelf seismic studies. All surfaces define the bases of fining upward sequences; they separate clay or biogenic muds below from authigenic glauconitic sandy muds or sands above. The entire Tertiary package is thoroughly bioturbated and dominated by ichnotaxa representing softground conditions. Burrow densities, burrow preservation, and the relative importance of certain ichnotaxa vary through the Tertiary package, reflecting changes in water depth, relative degree of condensation, and associated glaucony authigenesis, all related to margin progradation. Nonetheless, when individual sequences are considered...

Firmground Ichnofabrics in Deep-Water Sequence Stratigraphy, Tertiary Clinoform-Toe Deposits, New Jersey Slope

Other| June 01, 2001 Firmground Ichnofabrics in Deep-water Sequence Stratigraphy, Tertiary Clinoform-toe Deposits, New Jersey Slope CHARLES E. SAVRDA; CHARLES E. SAVRDA 1Department of Geology and Geography, 210 Petrie Hall, Auburn University, AL 36849-5305 Search for other works by this author on: GSW Google Scholar JAMES V. BROWNING; JAMES V. BROWNING 2Department of Geological Sciences, Rutgers University, Piscataway, NJ 08855-1179 Search for other works by this author on: GSW Google Scholar HANNELORE KRAWINKEL; HANNELORE KRAWINKEL 3Institut für Geologie und Paläontologie, Universität Stuttgart, Herdweg 51, D-70174 Stuttgart, Germany Search for other works by this author on: GSW Google Scholar STEPHEN P. HESSELBO STEPHEN P. HESSELBO 4Department of Earth Sciences, University of Oxford, Oxford OX1 3PR, UK Search for other works by this author on: GSW Google Scholar PALAIOS (2001) 16 (3): 294–305. https://doi.org/10.1669/0883-1351(2001)016<0294:FIIDWS>2.0.CO;2 Article history accepted: 25 Dec 2000 first online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation CHARLES E. SAVRDA, JAMES V. BROWNING, HANNELORE KRAWINKEL, STEPHEN P. HESSELBO; Firmground Ichnofabrics in Deep-water Sequence Stratigraphy, Tertiary Clinoform-toe Deposits, New Jersey Slope. PALAIOS 2001;; 16 (3): 294–305. doi: https://doi.org/10.1669/0883-1351(2001)016<0294:FIIDWS>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyPALAIOS Search Advanced Search Abstract Sixteen erosional surfaces are recognized in a 144-m-thick condensed package of Tertiary (Eocene-Pliocene) clinoform-toe sediments recovered at ODP Site 1073 on the New Jersey slope. Most of these surfaces are associated with significant hiatuses or extremely condensed intervals defined by Sr isotopes or biostratigraphic data, and many can be linked to sequence boundaries defined in onshore and shelf seismic studies. All surfaces define the bases of fining upward sequences; they separate clay or biogenic muds below from authigenic glauconitic sandy muds or sands above. The entire Tertiary package is thoroughly bioturbated and dominated by ichnotaxa representing softground conditions. Burrow densities, burrow preservation, and the relative importance of certain ichnotaxa vary through the Tertiary package, reflecting changes in water depth, relative degree of condensation, and associated glaucony authigenesis, all related to margin progradation. Nonetheless, when individual sequences are considered, little or no change in softground ichnofossil assemblages is recognized across bounding surfaces. However, most surfaces are marked clearly by firmground Thalassinoides, burrow systems that penetrate deeply (up to 2 m) into subjacent clays and are characterized by extremely sharp walls and coarser glauconitic fills. In shallower shelf sequences, firmground ichnofabrics develop at sequence boundaries in response to subaerial exposure and transgressive ravinement. In contrast, the Tertiary firmgrounds on the New Jersey margin formed in deep water in response to phases of rapid transgression and net erosion; consolidated mud substrates were exhumed as a result of sediment starvation and bottom-current winnowing, facilitated by bioerosion, at or near the bases of slope clinoforms. These observations extend the previously established sequence stratigraphic utility of the substrate-controlled Glossifungites ichnofacies to deeper water facies. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Formation and diagenesis of bedding cycles in uppermost Cretaceous chalks of the Dan Field, Danish North Sea

Metre‐scale lithologic cycles, visible in core and on logs from Maastrichtian chalks of the Dan Field, were examined to determine their mechanisms of deposition and relation to hydrocarbon production. The lower parts of cycles consist of porous, cream‐coloured, largely non‐stylolitic, commonly laminated chalk with limited bioturbation (mainly escape burrows). Cycles are capped by thinner intervals of white to grey, hard, stylolitic chalk with concentrations of bioclastic material, intense burrowing and few preserved primary sedimentary structures. The cycle caps contain nearly twice as much Mg as compared to the more porous parts of cycles and also have slightly larger δ18O values (−4·1‰ for the caps; −4·4‰ for porous zones). There is a significant reduction of average cycle thickness, as well as total thickness of the Maastrichtian chalk section, from SW to NE across the Dan Field. The cycle thinning largely results from a reduced thickness of porous chalks from the lower parts of cycles and thus is reflected in lower average porosity and permeability on the NE side of the field. These data indicate that episodic winnowing removed fine‐grained constituents from highstanding northeastern areas. Porous cycle bases were deposited at relatively high rates that precluded complete bioturbation; preserved laminae, coupled with escape burrows, reflect episodic sediment influx in areas that flank the seafloor highs. Cycle tops apparently accumulated more slowly (throughout the region, but especially on seafloor highs), perhaps because of reduced productivity of planktic organisms. Slower sedimentation allowed more complete bioturbation and destruction of sedimentary structures, and also led to incipient high‐magnesium calcite seafloor cementation (sufficient to yield firmer sediment and enhanced burrow preservation, but not to form true hardgrounds). Thus, the elevated magnesium contents and reduced porosity of the cycle caps reflect very early diagenetic processes that were only partially modified by burial diagenesis.Rates of chalk deposition, as inferred from physical and geochemical evidence, appear to be a significant control on reservoir characteristics in North Sea chalks. The highest average porosities and permeabilities are found in areas with the highest sediment accumulation rates where seafloor diagenesis is minimized. Topographic depressions at the time of sedimentation can thus be expected to have the best production characteristics, and synsedimentary topographic highs should have the thinnest sections and the poorest petrophysical properties.

Lungfish Burrows in the Upper Triassic Chinle and Dolores Formations, Colorado Plateau

ABSTRACT Vertical-to-inclined, cylindrical trace fossils that occur in the Upper Triassic Chinle and Dolores Formations on the Colorado Plateau are interpreted to be the casts of lungfish burrows. The casts, which are as much as 11 cm in diameter and as much as 1.6 m long, were formed by passive silicilastic and carbonate sedimentation into apparently abandoned lungfish burrows. Locally, the burrow fillings are overwhelmingly abundant, and many intersect and have destroyed former burrow fillings. Superposition of bioturbation episodes has obliterated most primary sedimentary structures. This bioturbation has contributed to the mottled coloration and the knobby-weathering texture of the rocks. The burrow-fillings occur ubiquitously in three lithofacies, comprising 1) purple- and white-mottled, ilicified sandstone and siltstone, 2) red and brown siltstone and mudstone, and 3) pink and green limestone. These strata were deposited in a continental environment that included fluvial channels and floodplains, sand sheets and playa mudflats, and lacustrine basins, marshes, and deltas. The identification of the trace fossils as the positive casts of lungfish burrows is based on their morphologic similarity to previously identified lungfish burrows and to available hand specimens. The widespread occurrence of the lungfish burrows in the Chinle and Dolores Formations attests to the extensive habitat that supported lungfish in the Late Triassic and to conditions favorable for burrow preservation. Analogy with the environments that support modern lungfish populations suggests that the Late Triassic climate in the study area provided sufficient moisture to support large populations of lungfish and that this climate was probably punctuated by seasonally dry periods.

Trace Fossils in Middle and Upper Austin Chalk near Dallas, Texas--Paleoecologic and Economic Significance: ABSTRACT

In outcrops throughout northeast Texas, the Austin Group consists of interbedded thin to very thick-bedded (0.3-1.5 m) chalk with thin intervening calcareous claystone (marl) layers. Both chalk and claystone are moderately to intensely bioturbated, and multiple generations of crosscutting burrows are common. Austin trace fossils occur as endogenic full-relief individuals filled with chalk, clay, or iron oxides. The abundance and diversity of ichnofossils within the Austin are in distinct contrast to the paucity of other megafossils, except large, locally conspicuous inoceramids with oyster epiliths. Variations in ichnofossil content, quality of burrow preservation, and petrographic character allow definition of three Austin substrate types. (1) Softground--vaguely mottled, argillaceous, foraminiferal biocalcilutite containing poorly preserved Planolites, Thalassinoides, and Chondrites. Burrowing is intense. Chondrites typically infests fillings of other ichnofossils. Inoceramids occur as widely scattered epifauna. (2) Bioclastic lenses--coarse-grained inoceramid biocalcirudite with interstitial chalk matrix. This lithology forms broad, low-relief channels; dense networks of Thalassinoides occur on lower surfaces. (3) Firmground--phosphatic, glauconitic, foraminiferal biocalcilutite containing well-preserved Rhizocorallium jenense and Pseudobilobites. South of Dallas, the disconfo mable Austin-Taylor contact is a Rhizocorallium-dominated firmground omission surface. The Austin contains a shallow marine (middle to inner shelf) ichno-assemblage. A vertical increase in the ratio of suspension to deposit-feeding burrows suggest that the Austin is a shallowing-upward sequence. Trace fossils impart textural heterogeneities to chalk which can either enhance or degrade reservoir quality and can also complicate wireline log interpretations and well completion procedures. End_of_Article - Last_Page 143------------

Sedimentologic Aspects of Bioturbation in Abyssal Atlantic Ocean: ABSTRACT

Relations between bioturbation features and sedimentologic aspects of abyssal pelagic ooze and clay were investigated in 26 box cores collected in 1,400 to 5,700 m of water in the central and southern Atlantic Ocean. Sediment composition, texture, and core stratigraphy were compared with the occurrences of biogenic structures and other aspects of bioturbation to determine the sedimentologic factors that most affect burrow preservation and biologic mixing of abyssal sediment. Box core surfaces typically exhibited a heterogeneous microtopography of mounds, lumps, trails, agglutinated tubes, and open holes. Benthic protists (foraminifera and xenophyophorids) and fecal strings of larger organisms were common. Remnants of shallow infaunal tunnel systems sometimes were evident on slightly washed box core surfaces. For example, Paleodictyon occurred in carbonate-rich ooze; Cosmorhaphe occurred in deposits containing 20 to 30% coarse fraction; and Spirorhaphe appeared to be cosmopolitan with respect to sediment type. Sediments of the mixed layer (upper 5 to 8 cm) and underlying Holocene transition layer were compared with respect to carbonate, organic carbon, and coarse fraction (> 62µm) percentages. Transition layer sediments, which contained the most visible burrows, were much more heterogeneous in terms of carbonate content than mixed layer deposits. However, the heterogeneity of organic carbon and coarse fraction concentrations were roughly equivalent in the two horizons. Visibility of specific burrows was highest in cores with low carbonate contents ( 70% CaCO3) throughout the entire core. End_of_Article - Last_Page 962------------

Selective preservation of burrows in deep-sea carbonates

Burrow preservation is a function of the rates of burrow production and burrow destruction and the rate of burial. These rates are related to water depth and therefore burrow preservation can be a depth indicator in deep-sea sediments. Box cores from fourteen localities in the eastern equatorial Pacific, taken from water depths of 3500–4850 m, showed a three-layer stratigraphy: a mixed layer with intense bioturbation (upper 5–7 cm), a transition layer (extending down to 20–35 cm), and a historical layer below. To be preserved, a burrow must reach below the mixed layer and into the transition layer. Abundance of vertical burrows is inversely proportional to water depth down to 4500 m, where vertical burrows disappear completely due to sediment shear and/or lack of burrow production. Within box cores the various burrow assemblages display an array of colors. Cross-cutting relationships of differently colored burrows help to establish a bioturbation chronology: burrow color fades with age. Two possible models for the observed burrow stratigraphy are presented: a steady-state model and a historical model. The steady-state model focuses on the activity of record-making burrowers versus the destruction of burrows by homogenizing burrowers, redox diagenesis and sediment flow. The historical model focuses on the effects of the early Holocene dissolution pulse on the observed burrow stratigraphy.